U.S. patent number RE39,437 [Application Number 10/455,358] was granted by the patent office on 2006-12-19 for negative thermal expansion glass ceramic.
This patent grant is currently assigned to Kabushiki Kaisha Ohara. Invention is credited to Naoyuki Goto, Ayako Yamaguchi.
United States Patent |
RE39,437 |
Yamaguchi , et al. |
December 19, 2006 |
**Please see images for:
( Certificate of Correction ) ** |
Negative thermal expansion glass ceramic
Abstract
A negative thermal expansion glass ceramic having a negative
coefficient of thermal expansion, which is a sufficiently large
absolute value in a temperature range of -40.degree. C. to
+160.degree. C. and a method for producing the same are provided.
The negative thermal expansion glass ceramic has a coefficient of
thermal expansion of -25 to -100.times.10.sup.-7/.degree. C. in the
temperature range of -40.degree. C. to +160.degree. C., and
comprises main crystalline phases which are one or more types
selected from a group consisting of .beta.-eucryptite solid
solution (.beta.-Li.sub.2O.cndot.Al.sub.2O.sub.3.cndot.2SiO.sub.2
solid solution), .beta.-eucryptite
(.beta.-Li.sub.2O.cndot.Al.sub.2O.sub.3.cndot.2SiO.sub.2),
.beta.-quartz solid solution (.beta.-SiO.sub.2) solid solution),
and .beta.-quartz (.beta.-SiO.sub.2), wherein a total amount of
crystals of the main crystalline phases can be 70 to 100% in mass
percent.
Inventors: |
Yamaguchi; Ayako (Sagamihara,
JP), Goto; Naoyuki (Sagamihara, JP) |
Assignee: |
Kabushiki Kaisha Ohara
(Sagamihara, JP)
|
Family
ID: |
27475724 |
Appl.
No.: |
10/455,358 |
Filed: |
September 3, 2003 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
09418754 |
Oct 15, 1999 |
6506699 |
|
|
Reissue of: |
09973785 |
Oct 11, 2001 |
06521556 |
Feb 18, 2003 |
|
|
Foreign Application Priority Data
|
|
|
|
|
Oct 23, 1998 [JP] |
|
|
10-302585 |
Jul 8, 1999 [JP] |
|
|
11-194799 |
Aug 30, 1999 [JP] |
|
|
11-243726 |
Oct 7, 1999 [JP] |
|
|
11-287138 |
|
Current U.S.
Class: |
501/4; 501/7;
428/426 |
Current CPC
Class: |
C03C
10/0027 (20130101); G02B 6/0218 (20130101); G02B
6/3854 (20130101) |
Current International
Class: |
C03C
10/04 (20060101); C03C 10/12 (20060101) |
Field of
Search: |
;501/4,7,8 ;428/426 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
0812810 |
|
Dec 1997 |
|
EP |
|
1 178336 |
|
Mar 2000 |
|
EP |
|
61-242931 |
|
Oct 1986 |
|
JP |
|
63-201034 |
|
Aug 1988 |
|
JP |
|
02-205256 |
|
Aug 1990 |
|
JP |
|
2-208256 |
|
Aug 1990 |
|
JP |
|
10-073740 |
|
Mar 1998 |
|
JP |
|
10-90555 |
|
Apr 1998 |
|
JP |
|
10-93827 |
|
Apr 1998 |
|
JP |
|
10-096827 |
|
Apr 1998 |
|
JP |
|
63-201034 |
|
Aug 1998 |
|
JP |
|
2000-266943 |
|
Sep 2000 |
|
JP |
|
WO 97/14983 |
|
Apr 1997 |
|
WO |
|
WO 97/26572 |
|
Jul 1997 |
|
WO |
|
WO 97/28480 |
|
Aug 1997 |
|
WO |
|
WO 99/06859 |
|
Feb 1999 |
|
WO |
|
WO 99/64898 |
|
Dec 1999 |
|
WO |
|
01/04672 |
|
Jan 2001 |
|
WO |
|
Other References
J Shyu et al., "Sintering, Crystallizaiton, and Properties of
B.sub.2O.sub.3/P.sub.2O.sub.5-Doped
Li.sub.2OAl.sub.2O.sub.34SiO.sub.2 Glass-Ceramics", Journal of the
American Ceramic Society, vol. 78, No. 8, Aug. 1, 1995, pp.
2161-2167. cited by examiner .
E.G. Wolff, "Thermal Expansion in Metal/Lithia-Alumina-Silica (LAS)
Composites", Ninth International Thermal Expansion Symposium,
Pittsburgh, PA, Dec. 8-10, 1996 (Abstract No. XP002131090). cited
by examiner .
Y. Hori et al., "Temperature-compensated Packages for Fiber Bragg
Gratings," IEICE Electronics, p. 231, Mar. 1997. (w/English
explanation). cited by other .
G. Muller et al., "Glass-ceramics based on phases with NZP-type
structure," Glastech. Ber., vol. 67, No. 9, pp. 255-259, Sep. 1994.
cited by other .
A. Sakamoto et al., "Ceramic Substrate with Negative Thermal
Expansion for Athermalization of Fiber Bragg Gratings," Technical
Report of IEICE, vol. 99, No. 278, pp. 71-76, Aug. 1999. (w/English
explanation). cited by other .
M. Kato et al., "The Package with Glass Ceramics of Thermal
Compensated Fiber Bragg Gratings," IEICE Electronics, p. 208, Mar.
1999. (w/English explanation). cited by other.
|
Primary Examiner: Group; Karl
Attorney, Agent or Firm: Oliff & Berridge PLC
Parent Case Text
This is a Division of application Ser. No. 09/418,754 filed Oct.
15, 1999 .Iadd.now U.S. Pat. No. 6,506,699.Iaddend.. The entire
disclosure of the prior application(s) is hereby incorporated by
reference herein in its entirety.
Claims
What is claimed is:
1. A negative thermal expansion glass ceramic, comprising: 5.5-15
mass percent of Li.sub.2O; and 0.5-4 mass percent of BaO; wherein
the negative thermal expansion glass ceramic has a coefficient of
thermal expansion of -25 to -100.times.10.sup.-7/.degree. C. in a
temperature range of -40.degree. C. to +160.degree. C.
2. The negative thermal expansion glass ceramic of claim 1,
comprising 40-65 mass percent of SiO.sub.2.
3. The negative thermal expansion glass ceramic of claim 1,
comprising 25-45 mass percent of Al.sub.2O.sub.3.
4. The negative thermal expansion glass ceramic of claim 1,
comprising a main crystalline phase which is at least one
crystalline phase selected from the group consisting of
.beta.-eucryptite solid solution, .beta.-eucryptite, .beta.-quartz
solid solution, and .beta.-quartz.
5. The negative thermal expansion glass ceramic of claim 4, wherein
a total amount of crystals of the main crystalline phase is 70 to
100% in mass percent.
6. The negative thermal expansion glass ceramic of claim 1, wherein
the glass ceramic is a material that is essentially free of
anisotropy.
7. The negative thermal expansion glass ceramic of claim 1, wherein
the glass ceramic is applied to a temperature compensating member,
the glass ceramic being combined with a material having a positive
coefficient of thermal expansion.
8. The negative thermal expansion glass ceramic of claim 1, wherein
the glass ceramic is applied to a device securing an optical
fiber.
9. The negative thermal expansion glass ceramic, comprising: 40-65
mass percent Of SiO.sub.2; 25-45 mass percent of Al.sub.2O.sub.3;
5.5-15 mass percent of Li.sub.2O; and 0.5-4 mass percent of BaO;
wherein the negative thermal expansion glass ceramic has a
coefficient of thermal expansion of -25 to
-100.times.10.sup.-7/.degree. C. in a temperature range of
-40.degree. C. to +160.degree. C.
10. The negative thermal expansion glass ceramic, comprising: 34-45
mass percent of Al.sub.2O.sub.3; and 0.5-4 mass percent of BaO;
wherein the negative thermal expansion glass ceramic has a
coefficient of thermal expansion of -25 to
-100.times.10.sup.-7/.degree. C. in a temperature range of
-40.degree. C. to +160.degree. C.
.Iadd.11. A temperature compensating member comprising: a negative
thermal expansion glass ceramic which comprises: 5.5-15 mass
percent of Li.sub.2O; and 0.5-4 mass percent of BaO; wherein the
negative thermal expansion glass ceramic has a coefficient of
thermal expansion of -25 to -100.times.10.sup.-7/.degree. C. in a
temperature range of -40.degree. C. to +160.degree. C..Iaddend.
.Iadd.12. A temperature compensating member comprising: a negative
thermal expansion glass ceramic which comprises: 34-35 mass percent
of Al.sub.2O.sub.3; and 0.5-4 mass percent of BaO; wherein the
negative thermal expansion glass ceramic has a coefficient of
thermal expansion of -25 to -100.times.10.sup.-7/.degree. C. in a
temperature range of -40.degree. C. to +160.degree. C..Iaddend.
.Iadd.13. A negative thermal expansion glass ceramic comprising:
34-45 mass percent of Al.sub.2O.sub.3; 0.5-4 mass percent of BaO;
and 40-65 mass percent of SiO.sub.2; wherein the negative thermal
expansion glass ceramic has a coefficient of thermal expansion of
-25 to -100.times.10.sup.-7/.degree. C. in a temperature of
-40.degree. C. to +160.degree. C..Iaddend.
.Iadd.14. The negative thermal expansion glass ceramic of claim 13,
comprising a main crystalline phase which is at least one
crystalline phase selected from the group consisting of
.beta.-eucryptite solid solution, .beta.-eucryptite, .beta.-quartz
solid solution, and .beta.-quartz..Iaddend.
.Iadd.15. The negative thermal expansion glass ceramic of claim 14,
wherein a total amount of crystals of the main crystalline phase is
70 to 100% in mass percent..Iaddend.
.Iadd.16. The negative thermal expansion glass ceramic of claim 13,
wherein the glass ceramic is a material that is essentially free of
anisotropy..Iaddend.
.Iadd.17. The negative thermal expansion glass ceramic of claim 13,
wherein the glass ceramic is applied to a temperature compensating
member, the glass ceramic being combined with a material having a
positive coefficient of thermal expansion..Iaddend.
.Iadd.18. The negative thermal expansion glass ceramic of claim 13,
wherein the glass ceramic is applied to a device securing an
optical fiber..Iaddend.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a negative thermal expansion glass
ceramic being able to be used for wide purposes in an
energy-related field, an information communication field, an
electronics field, being used as a temperature compensating member
in a device containing an optical fiber, such as an optical fiber
refractive index grating, a connector, or the like, and a method
for producing the same.
2. Description of Related Art
The optical technique is applied to not only a field of
communication systems, but also wide fields, such as precise
processing techniques, medical techniques, home electronic
products, or industrial electronics. With the optical technique,
emitting of light, condensing of light, transmission and divergence
of light, or the like are carried out by using the optical
fiber.
The various devices using the optical fiber are required to have a
structure which does not harm characteristics of the optical fiber
itself. That is, in order to prevent changing of the optical
properties, which is caused by expansion, contraction, or the like
of the optical fiber by a temperature change, it is required to
combine materials having a desired coefficient of thermal
expansion. For example, a device using a material having a negative
coefficient of thermal expansion has been proposed.
For example, Japanese Patent Laid-open No. Hei 10-90555 discloses
that a material having a negative coefficient of thermal expansion,
concretely, liquid crystal polymer is used at a flanged portion of
ferrule made of zirconia or stainless steel having a positive
coefficient of thermal expansion, in a single-core optical
connector.
WO Publication No. 97/14983 discloses an optical fiber diffraction
grating in which liquid crystal polymer having a negative
coefficient of thermal expansion covers peripheries of an optical
fiber having a positive coefficient of thermal expansion in order
to prevent the expanding and contracting caused by temperature
changes of the optical fiber. The disclosed liquid crystal polymer
(polyesteramide) has a coefficient of thermal expansion of
-1.8.times.10.sup.-5/.degree. C. to -7.2.times.10.sup.-6/.degree.
C.
Further, Japanese Patent Laid-open No. Hei 10-96827 discloses a
package in which an optical fiber being provided with a refractive
index grating is mounted to a supporting member having compositions
based on Zr-tungstate or Hf-tungstate having a negative coefficient
of thermal expansion. Concretely, a sintered body having a
coefficient of thermal expansion of -12.4.times.10.sup.-6/.degree.
C. is formed from ZrW.sub.2O.sub.8 powders having a coefficient of
thermal expansion of -4.7 to -9.4.times.10.sup.-6/.degree. C.
For various instruments or apparatus in the energy-related field,
an information field, or other fields, in order to prevent
occurring strain or internal stress by temperature differences, a
material is required, which is able to adjust the coefficient of
thermal expansion to desired values, of the devices or precision
parts constituting the instruments or the apparatus, moreover,
which enables satisfying dimensional precision, dimensional
stability, strength, thermal stability, or the like. Further, a
material is required, which is mixed with organic substances or
inorganic substances, for example, an adhesive, a sealing compound,
or the like used in the various devices or precision parts, which
enables adjusting the coefficient of thermal expansion to desired
values, of these substances. Moreover, the material is required to
satisfy the dimensional precision, the dimensional stability, the
strength, the thermal stability, or the like of these
substances.
For these materials, because of having a large heat resistance, a
small coefficient of thermal expansion, or the like, ceramics,
glass ceramics, glasses, metals, or other materials have been used.
However, these materials have the positive coefficient of thermal
expansion, that is, the materials have a property that they expand
when the temperature raises. Accordingly, these materials are not
necessarily optimum materials.
Therefore, for the materials used in the various devices or mixed
with the substances used in the various devices, a material which
has a negative coefficient of thermal expansion to negate the
positive coefficient of thermal expansion of other materials used
with the materials, the organic substances or the inorganic
substances is desired. That is, the material having a property of
contraction when the temperature raises is desired.
For the materials having the negative coefficient of thermal
expansion, generally, inorganic substances, such as
.beta.-eucryptite crystals, Li.sub.2O--Al.sub.2O.sub.3--SiO.sub.2
system ceramics containing the crystals,
Li.sub.2O--Al.sub.2O.sub.3--SiO.sub.2 system glass ceramics,
ZnO--Al.sub.2O.sub.3--SiO.sub.2 system glass ceramics, lead
titanium, hafnium titanium, zirconium tungstate, tantalum tangstate
have been known.
For example, Japanese Patent Laid-open No. Sho 63-201034 discloses
a method for producing a crystallized glass (glass ceramics) having
a negative coefficient of thermal expansion, wherein
Al.sub.2O.sub.3 and Li.sub.2O powders within an amount of a
specific range are mixed with powders of volcanic vitreous
deposits, the mixture is heated and melted, thereafter processed to
remove strain thereof, further reheated at a temperature of a
specific range for 12 to 24 hours, and thereafter annealed to
obtain the crystallized glass.
With the method, by varying conditions of the heat-treatment times
and heat-treatment temperatures, the crystallized glass having the
negative coefficient of thermal expansion of approximately
-60.times.10.sup.-7/.degree. C. is obtained, which is the largest
absolute value among obtained values.
However, the various materials in the publications, having the
negative coefficient of thermal expansion have various problems as
follows.
In the Japanese Patent Laid-open No. Hei 10-90555 and WO
Publication No. 97/14983, the liquid crystal polymer used as the
negative thermal expansion material is crystalline resin, so that
orientation of the crystal is high. For example, there is a problem
that warping is occurred in an injection-molded product. In
addition, there is a problem that values of physical properties,
such as the coefficient of thermal expansion, flexural strength,
modulus of elasticity, or other values differ according to
directions of the liquid crystal molecules.
The ZrW.sub.2O.sub.8 or HfW.sub.2O.sub.8 used as the temperature
compensating members in the Japanese Patent Laid-open No. Hei
10-96827 is not thermally stable within a wide temperature range
because a phase transition occurs therein at nearly 157.degree. C.
to occur a bending in a curve of thermal expansion.
The crystallized glass disclosed in the Japanese Patent Laid-open
No. Sho 63-201034 is made from the volcanic vitreous deposits, so
that contents of respective components, such as alkaline metal
oxides, alkaline earth oxides, and transition metal oxides expect
SiO.sub.2 and Li.sub.2O, which are main components and necessary to
deposit the main crystalline phase are not able to be adjusted.
Accordingly, it has disadvantages that it is difficult to avoid a
composition change, to deposit desired crystalline phase of a
desired amount, and to produce a crystallized glass having the
stable physical properties and qualities.
Further, as shown in the disclosed examples of the publication,
mixed powders are melted to be cullets, the cullets are ground and
melted again at 1600.degree. C. in the producing method.
Accordingly, the processes are complicated and the melting
temperature of the glass is very high, so that there are problems
that the production requires labors, times and costs.
Japanese Patent Laid-open No. Hei 2-208256 discloses low thermal
expansion ceramics of ZnO--Al.sub.2O.sub.3--SiO2 system, wherein
the main crystalline phases are .beta.-quartz solid solution and/or
zinc petalite solid solution. The ceramics, as shown in examples,
have the coefficient of thermal expansion of at lowest
-2.15.times.10.sup.6/.degree. C. (-21.5.times.10.sup.-7/.degree.
C.), so that the ceramics do not have a sufficiently low
coefficient of thermal expansion.
Further, because these ceramics contain a large amount of ZnO
component which is easy to sublime at a high temperature, it is
described in the publication that when a parent glass (base glass)
is formed, too long melting is not preferable. As shown in the
examples in the publication, the melting time is ten minutes which
is extremely short. However, in such a short time, even if the
temperature is high, the SiO.sub.2 and Al.sub.2O.sub.3 components
do not melt sufficiently to remain, so that it is difficult to
obtain a homogeneous parent glass. Accordingly, if the
heterogeneous parent glass is crystallized, the production of the
homogeneous ceramics is difficult.
When the raw materials are melted, if they are melted for hours as
an ordinary way, it is possible to solve the problem about the
residues. In this case, however, the ZnO component sublimes to vary
the composition of the parent glass, so that it is difficult to
obtain the ceramics which is stably homogeneous.
Further, the melting temperature in the example is 1620.degree. C.
which is high, so that there are the same problems as the producing
method disclosed in the Japanese Patent Laid-open No. Sho
63-201034.
As described above, because the earlier materials having the
negative coefficient of thermal expansion have some problems,
actually, they are less used in the energy-related field, the
information field, the optical communication field, or other
various fields.
SUMMARY OF THE INVENTION
The present invention was developed in view of the above-described
problems. Therefore, an object of the present invention is to
provide a negative thermal expansion glass ceramic having a
negative coefficient of thermal expansion which is a sufficiently
large absolute value in a general temperature range of -40.degree.
C. to +160.degree. C. when the glass ceramics are used in the
energy-related fields, the information field, the optical
communication field, or other fields, being able to be produced
with a low cost and stably regarding to compositions and physical
properties, and being able to be used as a temperature compensating
member. Another object of the present invention is to provide a
method for producing the same.
Inventors have made various efforts and experiments to solve the
problems above-described. As a result, it is found that
Li.sub.2O--Al.sub.2O.sub.3--SiO.sub.2--BaO system glass of a
specific composition range is subjected to a heat treatment to
crystallize, thereby the glass ceramic having a negative
coefficient of thermal expansion which is a large absolute value
and having little anisotropy is obtained. Then, the inventors have
achieved the invention.
In order to accomplish the above-described object, in one aspect of
the present invention, a negative thermal expansion glass ceramic
has a coefficient of thermal expansion of -25 to
-100.times.10.sup.-7/.degree. C. in a temperature range of
-40.degree. C. to +160.degree. C.
The negative thermal expansion glass ceramic can comprise main
crystalline phases which are one or more types selected from a
group consisting of .beta.-eucryptite solid solution
(.beta.-Li.sub.2O.cndot.Al.sub.2O.sub.3.cndot.2SiO.sub.2 solid
solution), .beta.-eucryptite
(.beta.-Li.sub.2O.cndot.Al.sub.2O.sub.3.cndot.2SiO.sub.2),
.beta.-quartz solid solution (.beta.-SiO.sub.2 solid solution), and
.beta.-quartz (.beta.-SiO.sub.2).
In the negative thermal expansion glass ceramic, a total amount of
crystals of the main crystalline phases can be 70 to 100% in mass
percent.
The negative thermal expansion glass ceramic can be produced by
subjecting a base glass to a heat treatment, wherein the base glass
can comprise, in mass percent, the following components:
TABLE-US-00001 SiO.sub.2 40-65% Al.sub.2O.sub.3 25-45% Li.sub.2O
5-15% B.sub.2O.sub.3 0-3% BaO 0.5-4% MgO 0-2% CaO 0-3% ZnO 0-6%
F.sub.2O.sub.5 0-4% ZrO.sub.2 0-4% TiO.sub.2 0-4% As.sub.2O.sub.3 +
Sb.sub.2O.sub.3 0-2%
and the base glass can be essentially free of PbO, Na.sub.2O, and
K.sub.2O.
The negative thermal expansion glass ceramic can be produced by
melting a base glass, quenching the molten glass, reducing the
quenched glass to powders to form, and firing the formed product to
crystallize, wherein the base glass can comprise, in mass percent,
the following components:
TABLE-US-00002 SiO.sub.2 40-65% Al.sub.2O.sub.3 25-45% Li.sub.2O
5-15% B.sub.2O.sub.3 0-3% BaO 0.5-4% MgO 0-2% CaO 0-3% ZnO 0-6%
F.sub.2O.sub.5 0-4% ZrO.sub.2 0-4% TiO.sub.2 0-4% As.sub.2O.sub.3 +
Sb.sub.2O.sub.3 0-2%
and the base glass can be essentially free of PbO, Na.sub.2O, and
K.sub.2O.
The negative thermal expansion glass ceramic can be produced by
melting a base glass, forming the molten glass, annealing the
formed glass as needed; and heating the formed product to
crystallize, wherein the base glass can comprise, in mass percent,
the following components:
TABLE-US-00003 SiO.sub.2 40-65% Al.sub.2O.sub.3 25-45% Li.sub.2O
5-15% B.sub.2O.sub.3 0-3% BaO 0.5-4% MgO 0-2% CaO 0-3% ZnO 0-6%
F.sub.2O.sub.5 0-4% ZrO.sub.2 0-4% TiO.sub.2 0-4% As.sub.2O.sub.3 +
Sb.sub.2O.sub.3 0-2%
and the base glass can be essentially free of PbO, Na.sub.2O, and
K.sub.2O.
The negative thermal expansion glass ceramic has the negative
coefficient of thermal expansion, which is a large absolute
value.
In addition, although the negative thermal expansion glass ceramic
has a crystallized region, this glass ceramic does not have a
specific orientation as a whole material, so that the negative
thermal expansion glass ceramic can be a material having little
anisotropy.
Accordingly, the negative thermal expansion glass ceramic can be
applied to a temperature compensating member, with combined with a
material having a positive coefficient of thermal expansion.
Particularly, the negative thermal expansion glass ceramic can be
suitably applied to a device securing an optical fiber.
According to the negative thermal expansion glass ceramic, the
glass ceramic can be used as a temperature compensating member with
combined with a material having a positive coefficient of thermal
expansion, thereby it can be possible to the utmost to prevent a n
adverse effect of temperature change of the devices or the
like.
As the devices securing the optical fiber, for example, the optical
fiber diffraction grating, the optical connector, or the like used
in the optical communication field can be included.
In accordance with another aspect of the invention, a method for
producing a negative thermal expansion glass ceramic, comprises the
steps of: melting a base glass; quenching the molten base glass;
reducing the quenched base glass to powders to form; and firing the
formed product at a temperature range of 1200.degree. C. to
1350.degree. C. to crystallize; wherein the base glass comprises,
in mass percent, the following components:
TABLE-US-00004 SiO.sub.2 40-65% Al.sub.2O.sub.3 25-45% Li.sub.2O
5-15% B.sub.2O.sub.3 0-3% BaO 0.5-4% MgO 0-2% CaO 0-3% ZnO 0-6%
F.sub.2O.sub.5 0-4% ZrO.sub.2 0-4% TiO.sub.2 0-4% As.sub.2O.sub.3 +
Sb.sub.2O.sub.3 0-2%
and the base glass is essentially free of PbO, Na.sub.2O, and
K.sub.2O.
In accordance with further aspect of the invention, a method for
producing a negative thermal expansion glass ceramic, comprises the
steps of: melting a base glass; forming the molten base glass;
annealing the formed base glass as needed; subjecting the formed
product to a heat treatment at a temperature range of 620.degree.
C. to 800.degree. C. to nucleate; and subjecting the resulting
product to a heat treatment at a temperature range of 700.degree.
C. to 950.degree. C. to crystallize; wherein the base glass
comprises, in mass percent, the following components:
TABLE-US-00005 SiO.sub.2 40-65% Al.sub.2O.sub.3 25-45% Li.sub.2O
5-15% B.sub.2O.sub.3 0-3% BaO 0.5-4% MgO 0-2% CaO 0-3% ZnO 0-6%
F.sub.2O.sub.5 0-4% ZrO.sub.2 0-4% TiO.sub.2 0-4% As.sub.2O.sub.3 +
Sb.sub.2O.sub.3 0-2%
and the base glass is essentially free of PbO, Na.sub.2O, and
K.sub.2O.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, features and advantages of the
invention will become more apparent from the following description
taken in conjunction with the accompanying drawings wherein like
references refer to like parts and wherein:
FIG. 1 is a sectional side view of an assembly in which a glass
ceramic according to an embodiment of the present invention is used
as a temperature compensating member; and
FIG. 2 is a SEM photograph (scanning electron microscope
photograph) showing a surface of a glass ceramic according to an
embodiment of the present invention.
PREFERRED EMBODIMENT OF THE INVENTION
Hereinafter, the negative thermal expansion glass ceramic according
to an embodiment of the present invention will be explained in
detail.
In the present invention, the glass ceramic means material obtained
by subjecting a glass to a heat treatment to deposit a crystalline
phase in a glass phase to obtain the material. The glass ceramic
includes not only the material which has both a glass phase and a
crystalline phase but also the material in which all glass phases
are phase-transited to crystalline phases, that is, the material in
which an amount of crystals is 100 mass %.
The main crystalline phases of the negative thermal expansion glass
ceramic according to the present invention are one or more types
selected from a group consisting of .beta.-eucryptite solid
solution (.beta.-Li.sub.2O.cndot.Al.sub.2O.sub.3.cndot.2SiO.sub.2
solid solution), .beta.-eucryptite
(.beta.-Li.sub.2O.cndot.Al.sub.2O.sub.3.cndot.2SiO.sub.2),
.beta.-quartz solid solution (.beta.-SiO.sub.2 solid solution), and
.beta.-quartz (.beta.-SiO.sub.2).
The solid solution of the .beta.-eucryptite or .beta.-quartz
crystals shows the one in which part of the crystals are
substituted and/or atoms invade between the crystals.
These main crystalline phases are important factors contributing
the coefficient of thermal expansion of the negative thermal
expansion glass ceramic according to the present invention. The
base glass is subjected to a heat treatment under determined
conditions to deposit the main crystalline phase having the
negative coefficient of thermal expansion in the glass phase having
positive coefficient of thermal expansion or to phase-transit the
all glass phases to crystalline phases containing the main
crystalline phase, so that it is possible to control the
coefficient of thermal expansion of the whole glass ceramic within
the desired values.
Types and deposited amounts of these main crystalline phases are
determined by a containing ratio of Li.sub.2O, Al.sub.2O.sub.3 and
SiO.sub.2 in the particular composition range, and by a firing
crystallization temperature or a crystallization temperature,
described later. In order to obtain the objective coefficient of
thermal expansion in the present invention, it is preferable that
the total amount of crystals of the main crystalline phases are in
the range of 70 to 100% in mass percent, while if it is below 70%,
the coefficient of thermal expansion may become higher than the
objective range in the present invention.
The composition of oxides of the negative thermal expansion glass
ceramic according to the present invention is expressed by the
composition of oxides of the base glass thereof. The reasons for
limiting the composition range of the base glass to the range
above-described will be explained as follows.
The SiO.sub.2, Li.sub.2O, and Al.sub.2O.sub.3 components are
important as constituents of the main crystalline phases which are
the .beta.-eucryptite solid solution, the .beta.-eucryptite, the
.beta.-quartz solid solution, and the .beta.-quartz.
The SiO.sub.2 component is a main component of the main crystals
having the negative coefficient of thermal expansion. When the
SiO.sub.2 content is below 40 mass %, it is difficult to
sufficiently deposit the desired main crystalline phases. On the
other hand, when the SiO.sub.2 content exceeds 65 mass %, the base
glass is difficult to melt and the glass melt is difficult to
refine, moreover, a crystalline phase other than the desired main
crystalline phases deposits. Accordingly, preferable range of the
SiO.sub.2 content is 40-65 mass %.
When the Al.sub.2O.sub.3 content is below 25 mass %, it is
difficult to melt the base glass, so that the homogeneity thereof
is deteriorated, and it becomes difficult to cause the desired main
crystalline phase to be produced with the required amount. On the
other hand, when the Al.sub.2O.sub.3 content exceeds 45 mass %, a
melting point becomes too high, so that it becomes difficult to
melt and the glass melt is difficult to refine. Thus, preferable
range of the Al.sub.2O.sub.3 content is 25-45 mass %.
When the Li.sub.2O content is below 5 mass %, it becomes difficult
to obtain the desired main crystalline phases of the required
amount, while the Li.sub.2O content exceeds 15 mass %, the
vitrification becomes difficult, further, the strength of the
heat-treated glass ceramics deteriorates. Accordingly, preferable
range of the Li.sub.2O content is 5-15 mass %.
The B.sub.2O.sub.3 component can be added at will for the purpose
of improving melting property of the base glass or other purpose,
however, this component forms the glass phase of the negative
thermal expansion glass ceramic of the present invention. Thus,
when the content thereof exceeds 3 mass %, which becomes obstacle
to form the desired main crystalline phases, so that the
coefficient of thermal expansion becomes larger than the objective
value thereof.
The BaO, MgO, ZnO, and CaO components are important as constituents
of the .beta.-eucryptite solid solution
(.beta.-Li.sub.2O.cndot.Al.sub.2O.sub.3.cndot.2SiO.sub.2 solid
solution) and the .beta.-quartz solid solution (.beta.-SiO.sub.2
solid solution), however, when the content of each components
exceeds 4 mass %, 2 mass %, 6 mass %, and 3 mass % respectively,
the coefficient of thermal expansion becomes large and it is
difficult to obtain the glass ceramic having the desired
coefficient of thermal expansion.
Among the respective components, the BaO component has effects to
prevent alloying platinum of a crucible with other metallic
elements in the base glass when the base glass is melted, and to
maintain the resistance to devitrification of the base glass.
However, when the BaO content is below 0.5 mass %, these effects
can not be obtained sufficiently and the resistance to
devitrification of the base glass is deteriorated, thus preferable
content of the BaO component is not less than 0.5 mass %.
The P.sub.2O.sub.5, ZrO.sub.2 and TiO.sub.2 components work as
nucleating agents of the crystals. When these contents of
respective components exceed 4 mass %, the base glass is difficult
to melt and the glass melt is difficult to refine, so that an
unmelted thing may occur in the glass. Accordingly, among the each
components, it is particularly preferable that the TiO.sub.2
content is up to 3.5 mass %, and the ZrO.sub.2 content is up to 2
mass %.
The As.sub.2O.sub.3 and Sb.sub.2O.sub.3 components can be added as
refining agents in the melting process of the base glass in order
to obtain the homogeneous products, however, the total amount of
these are sufficient up to 2 mass %.
Other ingredients, such as coloring components may be added in the
range of maintaining the desired properties of the glass ceramic of
the present invention.
It is preferable that the glass ceramic is practically free of the
PbO, Na.sub.2O, and K.sub.2O components, because the PbO component
requires costs for the environmental pollution control measure, and
because if the glass ceramics contain Na.sub.2O or K.sub.2O ions
thereof will diffuse at following steps, such as a film formation
or a cleaning, so that the physical properties of the negative
thermal expansion glass ceramic of the present invention vary.
It is preferable that the glass ceramic having the compositions
according to the present invention is produced by two methods
described as follows.
With both methods, the raw materials which are such as oxides,
carbonates, hydroxides, nitrates, or the like are weighed, mixed to
have the compositions above-described, respectively. The resulting
mixture is charged in a crucible or the like, and melted with
stirring at the temperature of about 1400-1500.degree. C. for about
6-8 hours to obtain the base glass in a refined state. Then, the
crystallization is performed by the two methods described as
follows.
In the first method, the obtained base glass with a molten state is
quenched by a roller quenching method, a water quenching method or
other methods.
Then, the quenched glass is reduced to powders by known milling
methods, such as a wet method or a dry method, using known mills,
such as a ball mill, a planetary ball mill, or a roller mill. It is
preferable that grain sizes of the glass powders are not more than
100 .mu.m maximally, average grain size thereof is not more than 10
.mu.m, and it is more preferable that the average grain size
thereof is not more than 5 .mu.m. When the maximal grain size
exceeds 100 .mu.m, a required temperature for firing
crystallization described later becomes high and the homogeneity
and closeness of the obtained glass ceramic deteriorate.
The glass powders obtained in this manner are formed into a desired
shape by known forming methods, such as a press forming. In the
forming process, polyvinylalcohol, stearic acid, polyethylene
glycol or the like can be added as an organic binder. Particularly,
in a case that the glass powders are formed into a large block-like
shape, the mixing of the organic binder is preferable. For example,
it is preferable that the organic binder solution, such as
polyvinylalcohol of concentration of about 1-5% is added 5-15 mass
% against the powders as 100 mass %.
After the forming, a treatment of the firing to crystallize is
carried out as a heat treatment. After the temperatures of the
formed products are raised, the formed products are retained at
1200-1350.degree. C. for about 2-10 hours to fire. Thereby, the
desired main crystalline phases are deposited. After the
crystallization by firing, because the crystals having the negative
coefficient of thermal expansion are deposited, if they are
quenched, cracks will be occurred. Therefore, it is preferable that
they are annealed at a rate of not more than 50.degree. C./hr.
In the case of performing the firing to crystallize, a retention at
the nucleation temperature is not required, which is differ from
the second method described later.
With the first method above-described, it is possible to obtain
easily the products having the negative coefficient of thermal
expansion, of which absolute values are remarkably large. Further,
because the formed products are made from powders, a production of
large size of products is possible.
Next, the second method will be explained.
The obtained base glass with molten state is cast in iron molds or
the like to form, thereafter, the formed glass is annealed as
needed, such as removing strains of the formed glass.
Then, the treatment of crystallization is carried out as a heat
treatment. At first, the base glass is subjected to the heat
treatment at the temperature of 620-800.degree. C. to stimulate the
nucleation. Neither if the nucleation temperature is lower than
620.degree. C. nor higher than 800.degree. C., nuclei of crystals
are not generated.
After the nucleation, the base glass is subjected to the heat
treatment at temperature of 700-950.degree. C. to crystallize When
the crystallization temperature is lower than 700.degree. C., the
main crystalline phases of the sufficient amount are not grown,
while when it is higher than 950.degree. C., the base glass is
melted and the crystals, such as .beta.-spodumene or the like
having large coefficient of thermal expansion are deposited, so
that these are undesirable. After the crystallization, as described
in the first method, it is preferable that the crystallized product
is annealed at the rate of not more than 50.degree. C./hr.
In the second method, compared with the first method in which the
powders are formed to fire, the processes of milling the base glass
and forming the powders are not required, so that it is possible to
reduce the costs and times, which the production requires. Further,
because the formed products do not contain pores, the glass ceramic
having higher strength is able to be obtained.
EXAMPLES
The negative thermal expansion glass ceramics according to the
examples of the present invention will be explained as follows.
However, the invention is, of course, not limited to the
examples.
Tables 1 and 2 show composition ratios, firing crystallization
temperatures and retention times, or nucleation temperatures and
retention times, crystallization temperatures and retention times,
of the glass ceramics according to the examples No. 1 to No. 7 of
the invention.
The glass ceramics according to the examples No. 1 to No. 7 were
produced as follows.
At first, the raw materials which were such as oxides, carbonates,
hydroxides, nitrates, or the like were weighed and mixed to have
the compositions in Tables 1 and 2, respectively, charged in a
platinum crucible, melted with stirring at the temperatures of
about 1400-1550.degree. C. for 6-8 hours, using a general apparatus
for melting.
Thereafter, with regard to examples No. 1, No. 2, and No. 3, the
base glasses in molten state were quenched by submerging.
Subsequently, the obtained formed products of glasses were reduced
to powders having the average grain size of approximately 5 .mu.m
by an alumina ball mill.
Then, the organic binder was added to the powders and the powders
were formed by an uniaxial pressing.
Thereafter, resulting compacts were put in a furnace, heated to
raise temperatures and retained at the firing crystallization
temperatures shown in Table 1 for the determined times to
crystallize, thereafter, annealed at the rate of not more than
50.degree. C./hr. Thus, the glass ceramics were obtained.
With regard to examples No. 4, No. 5, No. 6 and No. 7, the base
glasses in the molten state were cast in the iron molds to form,
thereafter annealed, thus the formed products of glasses were
obtained, respectively.
Thereafter, the formed products of glasses were not milled, but put
in the furnace, heated to raise temperatures and retained at the
nucleation temperatures shown in Table 2 for the determined times
to generate nuclei of the crystals. Subsequently, the resulting
products were heated to raise temperatures and retained at the
crystallization temperatures shown in Table 2 for the determined
times to crystallize, thereafter annealed at the rate of not more
than 50.degree. C./hr. Thus, the glass ceramics were obtained.
From the glass ceramics according to the respective examples
obtained as above-described, samples having diameter of 5 mm and
length of 20 mm were cut out, and measured the coefficient of
thermal expansion in the temperature range of -40.degree. C. to
+160.degree. C. by RIGAKU Inc. TAS200 thermomechanical analytical
instrument.
The total amounts of crystals of the main crystalline phases of
these glass ceramics were calculated from peak areas obtained by
powder X-ray diffraction method.
The results are shown in Tables 1 and 2.
Prior glass ceramics as comparative examples No. 1 to No. 3 are
shown in Table 3, similarly in Tables 1 and 2.
The glass ceramics of the comparative examples No. 1 and No. 2 were
produced by the same method as that of the examples No. 4 to No. 7,
and the glass ceramics of the comparative example No. 3 were
produced by the same method as that of the examples No. 1 to No.
3.
The coefficients of thermal expansion and the total amounts of
crystals of the main crystalline phases of the glass ceramics of
comparative examples were measured by the same method as
above-described, and the results thereof are shown in Table 3.
TABLE-US-00006 TABLE 1 Examples No. 1 2 3 Glass composition (in
mass %) SiO.sub.2 47.0 46.0 48.0 Al.sub.2O.sub.3 40.0 40.0 38.0
Li.sub.2O 12.0 12.0 11.0 B.sub.2O.sub.3 1.0 BaO 1.0 1.0 0.5 MgO 0.5
ZnO 1.0 1.0 Total amount of crystals of main 95 85 70 crystalline
phases (in mass %) 3250 1300 1250 Firing crystallization
temperature (.degree. C.) Retention time (hr) 7 4 4 Coefficient of
thermal -93 -73 -36 expansion (.times.10.sup.-7/.degree. C.)
(-40.degree. C. to +160.degree. C.)
TABLE-US-00007 TABLE 2 Examples No. 4 5 6 7 Glass composition (in
mass %) SiO.sub.2 46.5 57.0 59.5 47.4 Al.sub.2O.sub.3 39.5 25.0
25.0 34.6 Li.sub.2O 11.5 5.5 5.0 33.0 BaO 0.5 1.0 0.5 2.0 CaO 0.5
2.0 ZnO 6.0 4.5 P.sub.2O.sub.5 0.5 TiO.sub.2 1.0 2.5 2.5 2.0
ZrO.sub.2 0.5 2.0 2.0 0.5 As.sub.2O.sub.3 1.0 Sb.sub.2O.sub.3 0.5
0.5 Total amount of crystals of 90 80 80 85 main crystalline phases
(in mass %) Nucleation temperature 640 700 720 640 (.degree. C.)
Retention time (hr) 5 5 5 5 Crystallization 720 780 800 720
temperature (.degree. C.) Retention time (hr) 5 5 5 5 Coefficient
of thermal -96 -28 -26 -80 expansion (.times.10.sup.-7/.degree. C.)
(-40.degree. C. to +160.degree. C.)
TABLE-US-00008 TABLE 3 Comparative examples No. 1 2 3 Glass
composition (in mass %) SiO.sub.2 57.5 56.5 46.0 Al.sub.2O.sub.3
24.0 26.3 38.0 Li.sub.2O 7.0 5.0 11.0 B.sub.2O.sub.3 4.0 BaO 3.0
0.5 MgO 1.0 1.0 ZnO 2.0 1.5 0.5 F.sub.2O.sub.5 4.9 TiO.sub.2 2.5
2.3 ZrO.sub.2 2.0 2.0 As.sub.2O.sub.3 1.0 0.5 Total amount of
crystals of main 65 65 40 crystalline phases (in mass %) Nuclation
temperature (.degree. C.) 700 700 Retention time (hr) 5 5
Crystallization temperature (.degree. C.) 780 780 Retention time
(hr) 5 5 Firing crystallization 1200 temperature (.degree. C.)
Retention time (hr) 4 Coefficient of thermal expansion -6 -2 -5
(.times.10.sup.-7/.degree. C.) (-40.degree. C. to +160.degree.
C.)
As shown in Tables 1 and 2, the glass ceramics according to the
examples of the present invention have the coefficients of thermal
expansion of -26 to -96.times.10.sup.-7/.degree. C. which are very
large negative absolute values.
As a result of the X-ray diffractometry, the main crystalline phase
of the glass ceramics of the examples No. 1 and No. 7 are the
.beta.-eucryptite
(.beta.-Li.sub.2O.cndot.Al.sub.2O.sub.3.cndot.2SiO.sub.2), the main
crystalline phases of the examples No. 2, No. 3, and No. 4 are the
.beta.-eucryptite solid solution
(.beta.-Li.sub.2O.cndot.Al.sub.2O.sub.3.cndot.2SiO.sub.2 solid
solution), and the main crystalline phases of the examples No. 5
and No. 6 are the .beta.-quartz solid solution (.beta.-SiO.sub.2
solid solution).
On the other hand, as a result of the X-ray diffractometry, the
.beta.-quartz solid solution is deposited in the comparative
examples No. 1, No. 2, and No. 3, so that the glass ceramics have
the negative coefficients of thermal expansion, as shown in Table
3, however, it is not possible to obtain the glass ceramics having
the negative coefficients of large absolute values.
The glass ceramic obtained in example No. 4 was cut and polished,
to make a plane plate 1 having a dimension of length of 30
mm.times.width of 15 mm.times.thickness of 2 mm and a cover plate 2
of the same dimension, as temperature compensating members. A
groove for setting the optical fiber was cut in the top surface of
the plane plate 1 by a diamond saw.
Then, an optical fiber 4 of quartz system, having a refractive
index grating 3 of length of 10 mm was fitted in the groove so that
the refractive index grating 3 would position at the center of the
plane plate 1.
Then, in a state that the optical fiber 4 and the refractive index
grating 3 were covered with the cover plate 2, the plane plate 1
and the cover plate 2 were bonded to join by using adhesives, so
that an assembly 5 shown in FIG. 1 was made. For the joining,
conventionally known adhesive, such as the thermally cured resin of
epoxy or the like can be used. In this example, thermally cured
epoxy adhesive was used.
An assembly which was the same as the one in FIG. 1 was made by
using the comparative example No. 1 (not shown).
Reflection wavelengths obtained from the respective refractive
index gratings of the assembly 5 in FIG. 1 and of the assembly with
the comparative example No. 1 were measured with varying the
temperatures in the range of -40.degree. C. to +100.degree. C., and
compared each other. As a result, with the assembly 5 using the
glass ceramic according to the present invention, temperature
dependence of the reflection wavelength from the refractive index
grating was drastically reduced and stable reflection wavelengths
were obtained within the temperature range, compared with the
assembly using the glass ceramic of the comparative example No.
1.
A SEM photograph (scanning electron microscope photograph) is shown
in FIG. 2, which was taken after the surface of the glass ceramic
of example No. 2 was mirror polished and etched by hydrofluoric
acid. As shown in FIG. 2, crystal grains which are deposited in the
glass ceramic disperse three-dimensionally without having the
orientation. Accordingly, it is presumed that the glass ceramic of
example No. 2 has little anisotropy inside.
As described above, the negative thermal expansion glass ceramic of
the present invention have coefficient of thermal expansion of -25
to -100.times.10.sup.-7/.degree. C. in the temperature range of
-40.degree. C. to +160.degree. C., that is, the glass ceramic has
the negative coefficient of thermal expansion which is a
sufficiently large absolute value. Accordingly, in optical
fiber-related devices, such as an optical fiber refractive index
grating or a connector of optical fiber in the optical
communication field or the like, influences by the temperature
changes can be prevented to the utmost by using the glass ceramic,
with combining with a material having a positive coefficient of
thermal expansion, so that the glass ceramic can function as
temperature compensating members. Further, because the glass
ceramic has little anisotropy as a material, the problems caused by
the anisotropy in the forming process or the problems of variation
of the physical properties are not occurred, thereby it is possible
to suitably apply the glass ceramic to the devices related to the
optical fiber, compared with the prior liquid crystal polymer or
the like.
Further, because of the negative thermal expansion, the glass
ceramic can be used as bulk-like materials in the wide use in the
energy-related field, the information communication field, the
electronics field of other fields.
The negative thermal expansion glass ceramic according to the
present invention is milled by the known mills, such as a ball
mill, a vibrating mill, a roller mill, or a jet mill to have grain
sizes of not more than 100 .mu.m, preferably not more than 50
.mu.m, and mixed with the organic substances or inorganic
substances used in the respective fields, thereby the coefficients
of thermal expansion of these substances are reduced. Therefore,
the milled glass ceramic can be used as a filler for reducing the
thermal expansion, which is superior in dimension stability.
These organic substances and the inorganic substances are, not
limited, for example, phenol resin, epoxy resin, polyamide resin,
polycarbonate resin, or low-melting point glass. These also have
wide uses, such as an industrial use or an architectural use.
The negative thermal expansion glass ceramic according to the
present invention can be produced by melting the base glass at a
relatively low temperature compared with the prior technology,
thereby it is possible to produce the glass ceramic with the low
cost. Moreover, the glass ceramic contains the components which can
easily control the composition ratio, but does not contain the
components which are unstable in the composition, so that the glass
ceramic can be produced stably in terms of the composition and
physical properties.
From the foregoing description, one skilled in the art can easily
ascertain the essential characteristics of this invention, and
without departing from the spirit and scope thereof, can make
various changes and modifications of the invention to adapt it to
various usage and conditions.
The entire disclosure of Japanese Patent Application No. Hei
10-302585 filed on Oct. 23, 1998, No. Hei 11-194799 filed on Jul.
8, 1999, No. Hei 11-243726 filed on Aug. 30, 1999 and No. Hei
11-287138 filed on Oct. 7, 1999 including specifications, claims,
drawings and summaries are incorporated herein by reference in its
entirety.
* * * * *