JPH05105508A - Glass-mullite whisker composite board and its production - Google Patents
Glass-mullite whisker composite board and its productionInfo
- Publication number
- JPH05105508A JPH05105508A JP3271535A JP27153591A JPH05105508A JP H05105508 A JPH05105508 A JP H05105508A JP 3271535 A JP3271535 A JP 3271535A JP 27153591 A JP27153591 A JP 27153591A JP H05105508 A JPH05105508 A JP H05105508A
- Authority
- JP
- Japan
- Prior art keywords
- thermal expansion
- mullite
- glass
- mechanical strength
- mullite whisker
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 229910052863 mullite Inorganic materials 0.000 title claims abstract description 47
- 239000002131 composite material Substances 0.000 title claims abstract description 16
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 4
- KZHJGOXRZJKJNY-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Si]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O KZHJGOXRZJKJNY-UHFFFAOYSA-N 0.000 claims abstract description 41
- 239000011521 glass Substances 0.000 claims abstract description 14
- 239000000843 powder Substances 0.000 claims abstract description 14
- 239000000203 mixture Substances 0.000 claims abstract description 3
- 239000000758 substrate Substances 0.000 claims description 16
- 238000010304 firing Methods 0.000 claims description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 abstract description 12
- 229910052710 silicon Inorganic materials 0.000 abstract description 9
- 239000010703 silicon Substances 0.000 abstract description 9
- 229910052906 cristobalite Inorganic materials 0.000 abstract description 5
- 239000011230 binding agent Substances 0.000 abstract description 3
- 230000000694 effects Effects 0.000 abstract description 3
- 239000011347 resin Substances 0.000 abstract description 2
- 229920005989 resin Polymers 0.000 abstract description 2
- 238000001354 calcination Methods 0.000 abstract 2
- 238000000465 moulding Methods 0.000 abstract 1
- 239000005388 borosilicate glass Substances 0.000 description 12
- 229910021493 α-cristobalite Inorganic materials 0.000 description 7
- 125000001475 halogen functional group Chemical group 0.000 description 5
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 3
- 239000000919 ceramic Substances 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000007606 doctor blade method Methods 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 239000011268 mixed slurry Substances 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000012827 research and development Methods 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 229910021494 β-cristobalite Inorganic materials 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K1/00—Printed circuits
- H05K1/02—Details
- H05K1/03—Use of materials for the substrate
- H05K1/0306—Inorganic insulating substrates, e.g. ceramic, glass
Landscapes
- Compositions Of Oxide Ceramics (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、例えば回路基板、特に
ＬＳＩ素子の実装に用いられるガラス・ムライトウィス
カー複合基板に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, a circuit board, and more particularly to a glass / mullite whisker composite board used for mounting an LSI element.
【０００２】[0002]
【従来の技術】従来より回路基板としてアルミナ基板が
使用されて来ているが、ＬＳＩ素子の高速化が進むにつ
れて素子間を結ぶ配線の信号伝播遅延が無視できなくな
り、誘電率の大きな（１ＭＨｚでの誘電率は９．５）ア
ルミナ基板は高周波回路等には不適であると言われてい
る。すなわち、信号を高速伝播させる為には基板材料の
誘電率は低いことが望まれており、又、素子を裸で基板
に直接高密度に搭載できるように熱膨張係数がシリコン
に近く、かつ、ＣｕやＡｕといった融点の低い電極材料
と同時焼成できるように１０００℃以下の低い温度で焼
結できることが要求されている。2. Description of the Related Art Conventionally, an alumina substrate has been used as a circuit substrate. However, as the speed of LSI devices has increased, the signal propagation delay of the wiring connecting the devices cannot be ignored and the dielectric constant is large (at 1 MHz). It is said that the alumina substrate is not suitable for high frequency circuits and the like. That is, in order to propagate a signal at high speed, it is desired that the dielectric constant of the substrate material is low, and that the coefficient of thermal expansion is close to that of silicon so that the element can be directly mounted on the substrate in a high density without being exposed, and It is required to be able to sinter at a low temperature of 1000 ° C. or lower so that it can be co-fired with an electrode material having a low melting point such as Cu or Au.
【０００３】このような要求を満足させる為に研究開発
が鋭意押し進められており、例えば低融点ガラスフリッ
トと無機耐火物フィラーとからなる低温焼成基板が提案
されている。In order to satisfy such requirements, research and development have been earnestly promoted, and for example, a low temperature fired substrate composed of a low melting point glass frit and an inorganic refractory filler has been proposed.
【０００４】[0004]
【発明が解決しようとする課題】しかしながら、前記提
案の基板は、強度の特性が充分でなく、又、熱膨張の大
きいクリストバライトが生成するという問題点があっ
た。そこで、本発明の目的は、回路基板としての機械的
強度が充分に有り、かつ、熱膨張係数がシリコンに近
く、さらには誘電率が低く、そして低温焼成が可能な基
板を提供することである。However, the above-mentioned substrate has problems that the strength characteristics are not sufficient and that cristobalite having a large thermal expansion is produced. Therefore, an object of the present invention is to provide a substrate which has sufficient mechanical strength as a circuit board, has a thermal expansion coefficient close to that of silicon, has a low dielectric constant, and can be fired at a low temperature. ..
【０００５】[0005]
【課題を解決する為の手段】前記本発明の目的は、ガラ
ス粉末５０〜９５重量部とムライトウィスカー５０〜５
重量部とを含有することを特徴とするガラス・ムライト
ウィスカー複合基板によって達成される。又、ガラス粉
末５０〜９５重量部とムライトウィスカー５０〜５重量
部との混合物を焼成することを特徴とするガラス・ムラ
イトウィスカー複合基板の製造方法によって達成され
る。The object of the present invention is to provide glass powder in an amount of 50 to 95 parts by weight and mullite whiskers 50 to 5 parts by weight.
And a glass-mullite whisker composite substrate. Further, it is achieved by a method for manufacturing a glass-mullite whisker composite substrate, which comprises firing a mixture of 50 to 95 parts by weight of glass powder and 50 to 5 parts by weight of mullite whiskers.
【０００６】尚、ガラス粉末とムライトウィスカーとの
配合割合は、ガラス粉末が５５〜６５重量部で、ムライ
トウィスカーが４５〜３５重量部のものであることが好
ましい。以下、本発明について詳しく説明する。例え
ば、ホウケイ酸ガラス粉末にムライトウィスカーを添加
し、バインダを用いてグリーンシートを作成し、１００
０℃で焼成させた複合セラミックスにおいて、ムライト
ウィスカーの添加量によってどのような変化が起きたか
をＸ線回折によって調べた所、ムライトウィスカーの添
加量が０のときは、熱膨張の大きなα−クリストバライ
トのピークだけが観察され、ホウケイ酸ガラスに観察さ
れるハローはほとんど確認できなかった。しかしなが
ら、ムライトウィスカーの添加量を少しづつ増加させて
行った所、α−クリストバライトのピークが徐々に小さ
くなり、ムライトのピークのなかでも強度の強いピーク
が表れてくることが判って来た。尚、ムライトウィスカ
ーの添加量が３ｗｔ％程度ではα−クリストバライトと
ムライトとが混在し、非晶質のホウケイ酸ガラスも存在
する。ムライトウィスカーの添加量が４ｗｔ％程度にな
ると、α−クリストバライトは大幅に減少し、ホウケイ
酸ガラスのハローがはっきりと表れる。この知見より、
ムライトウィスカーはホウケイ酸ガラスにおけるα−ク
リストバライト生成を抑制する効果があることが判明し
て来た。そして、ムライトウィスカーの添加量が５ｗｔ
％を超えるとα−クリストバライトのピークは消滅し、
ホウケイ酸ガラスのハローピークとムライトのピークだ
けが観察されたのである。The mixing ratio of the glass powder and the mullite whiskers is preferably 55 to 65 parts by weight of the glass powder and 45 to 35 parts by weight of the mullite whiskers. Hereinafter, the present invention will be described in detail. For example, mullite whiskers are added to borosilicate glass powder, and a green sheet is prepared by using a binder, and 100
In the composite ceramics fired at 0 ° C., what kind of change was caused by the addition amount of mullite whiskers was examined by X-ray diffraction. Was observed, and the halo observed in the borosilicate glass was hardly confirmed. However, when the addition amount of mullite whiskers was increased little by little, it was found that the peak of α-cristobalite gradually became smaller and a strong peak among mullite peaks appeared. When the addition amount of mullite whiskers is about 3 wt%, α-cristobalite and mullite are mixed and amorphous borosilicate glass is also present. When the amount of mullite whiskers added was about 4 wt%, α-cristobalite was significantly reduced and the halo of borosilicate glass was clearly visible. From this knowledge,
It has been found that mullite whiskers have an effect of suppressing α-cristobalite formation in borosilicate glass. And the addition amount of mullite whiskers is 5 wt.
%, The peak of α-cristobalite disappears,
Only the halo and mullite peaks of the borosilicate glass were observed.
【０００７】ところで、α−クリストバライトの（１０
１）のピークは２θが略２２°にあり、ホウケイ酸ガラ
スのハロー頂点の角度と一致する。そして、ムライトウ
ィスカーの添加量を減らしていくと、このブロードなハ
ローが尖ってくるような形でクリストバライトのピーク
が表れる。このクリストバライトは良く知られているよ
うにＳｉＯ2 の結晶の一つであるが、高温型のα−クリ
ストバライトから低温型のβ−クリストバライトへと２
００℃付近を境に可逆転移し、同時に熱膨張係数が大き
く変化する。ムライトウィスカーの添加量が４ｗｔ％以
下ではクリストバライトの生成量に応じて熱膨張率が大
きく、シリコンの熱膨張特性との相違が大きいものの、
ムライトウィスカーの添加量が５ｗｔ％を越えた位置で
は熱膨張率が急激に低下し、シリコンの熱膨張特性に近
いものとなって来る。By the way, α-cristobalite (10
In the peak of 1), 2θ is approximately 22 °, which coincides with the angle of the halo apex of borosilicate glass. Then, as the addition amount of mullite whiskers is reduced, the peak of cristobalite appears in a shape in which this broad halo sharpens. As is well known, this cristobalite is one of the crystals of SiO 2 , but from high temperature type α-cristobalite to low temperature type β-cristobalite, 2
Reversible transition occurs at around 00 ° C, and at the same time, the thermal expansion coefficient changes greatly. When the addition amount of mullite whiskers is 4 wt% or less, the coefficient of thermal expansion is large according to the amount of cristobalite produced, and although the difference from the thermal expansion characteristics of silicon is large,
At a position where the added amount of mullite whiskers exceeds 5 wt%, the coefficient of thermal expansion sharply decreases, and the thermal expansion coefficient comes close to that of silicon.
【０００８】このことは、ホウケイ酸ガラス粉末にムラ
イトウィスカーを５ｗｔ％〜５０ｗｔ％添加させること
により、シリコンの熱膨張特性に近いものとすることが
出来たことを示している。次に、ホウケイ酸ガラスにム
ライトウィスカーを添加した複合セラミックスの誘電率
を調べた所、ムライトウィスカーの添加量が多くなって
も、例えば５０ｗｔ％程度添加されてなるものでもそれ
程の変化はなく、アルミナの誘電率に比べれば約半分程
度のものであった。このことは、ガラス粉末とムライト
ウィスカーとの複合材料が高周波回路等の基板に適した
ものであることを推察できるのである。This indicates that by adding 5 wt% to 50 wt% of mullite whiskers to the borosilicate glass powder, the thermal expansion characteristics of silicon could be approximated. Next, when the dielectric constant of the composite ceramic in which mullite whiskers were added to borosilicate glass was examined, no significant change was observed even if the amount of mullite whiskers added increased, for example, even if it was added at about 50 wt%, It was about half of the dielectric constant of. From this, it can be inferred that the composite material of glass powder and mullite whiskers is suitable for a substrate such as a high-frequency circuit.
【０００９】さらに、ホウケイ酸ガラスにムライトウィ
スカーを添加した複合セラミックスの機械的強度を調べ
た所、ムライトウィスカーの添加量が多くなると機械的
強度も向上した。ところが、ムライトウィスカーの添加
量が５０ｗｔ％を越えると、逆に機械的強度が急激に低
下し始めた。このことは、ガラス粉末とムライトウィス
カーとの複合材料を高周波回路等の基板として利用する
為には、ムライトウィスカーの添加量が５０ｗｔ％以下
であることが大事であることを示している。特に、ムラ
イトウィスカーの添加量が３５ｗｔ％〜４５ｗｔ％であ
ることが好ましいものであった。Further, when the mechanical strength of the composite ceramics obtained by adding mullite whiskers to borosilicate glass was investigated, the mechanical strength was improved when the amount of mullite whiskers added was increased. However, when the amount of mullite whiskers added exceeded 50 wt%, the mechanical strength on the contrary began to drop sharply. This indicates that in order to use the composite material of glass powder and mullite whiskers as a substrate for a high-frequency circuit or the like, the addition amount of mullite whiskers is 50 wt% or less. In particular, it was preferable that the addition amount of mullite whiskers was 35 wt% to 45 wt%.
【００１０】又、ムライトウィスカーの添加量が５０ｗ
ｔ％以下、特に３５ｗｔ％〜４５ｗｔ％の場合には、１
０００℃以下の低温焼成によっても焼結密度が高いもの
であった。尚、ムライトウィスカーの代わりにムライト
粉末を用いた場合の複合材では、上記した本発明の特長
を発揮できないものであった。The addition amount of mullite whiskers is 50w.
t% or less, particularly in the case of 35 wt% to 45 wt%, 1
The sintered density was high even by low temperature firing at 000 ° C or lower. The composite material obtained by using mullite powder in place of mullite whiskers could not exhibit the above-mentioned features of the present invention.
【００１１】[0011]
【実施例】平均粒径３μｍのホウケイ酸ガラス粉末とア
スペクト比１０のムライトウィスカーとを表−１に示す
割合で有機溶剤中において超音波分散させた後、バイン
ダ樹脂を添加してボールミルで１０時間混合した。得ら
れた混合スラリーをドクターブーレード法にて成形して
グリーンシートを作成し、その後１０００℃で３時間焼
成し、ガラス・ムライトウィスカー複合材からなるＬＳ
Ｉ素子の実装に用いられる回路基板を得た。EXAMPLE Borosilicate glass powder having an average particle size of 3 μm and mullite whiskers having an aspect ratio of 10 were ultrasonically dispersed in an organic solvent at a ratio shown in Table 1, a binder resin was added, and a ball mill was used for 10 hours. Mixed. The obtained mixed slurry is formed into a green sheet by forming a green sheet by the doctor blade method, and then baked at 1000 ° C. for 3 hours to form an LS made of a glass / mullite whisker composite material.
A circuit board used for mounting the I element was obtained.
【００１２】このようにして得られた回路基板の特性の
評価結果を表−１に示す。 表−１ ムライトウィスカー 誘電率 熱膨張率（20〜400 ℃） 強度 密度 ｗｔ％ １ＭHz ×10-6／℃ ＭPa ％ ０ ４．０ ２．１ 60 100 比較例 ３５ ４．６ ３．０ 250 ９７ 実施例 ４５ ５．１ ３．２ 300 ９５ 実施例 ５５ ５．２ ３．２ 150 ９０ 比較例 これによれば、ホウケイ酸ガラスにムライトウィスカー
を添加したことにより、アルミナの誘電率９．５に対し
て著しい低誘電率化が図れ、又、熱膨張率がシリコンに
近いものであり、そしてムライトウィスカーの添加量が
３５ｗｔ％〜４５ｗｔ％にあっては機械的強度が大幅に
向上しており、ＬＳＩ素子の実装に用いられる回路基板
として好適なものであることが判る。Table 1 shows the evaluation results of the characteristics of the circuit board thus obtained. Table-1 Mullite whiskers Dielectric constant Thermal expansion coefficient (20 to 400 ° C) Strength Density wt% 1MHz × 10 -6 / ° C MPa% 0 4.0 2.1 60 100 Comparative example 35 4.6 3.0 3.0 250 97 Implementation Example 45 5.1 3.2 300 95 Example 55 5.2 3.2 150 90 Comparative Example According to this, by adding mullite whiskers to borosilicate glass, the dielectric constant of alumina was 9.5. A significantly low dielectric constant can be achieved, the coefficient of thermal expansion is close to that of silicon, and the mechanical strength is significantly improved when the amount of mullite whiskers added is 35 wt% to 45 wt%. It can be seen that it is suitable as a circuit board used for mounting.
【００１３】[0013]
【効果】本発明になるガラス・ムライトウィスカー複合
基板は、誘電率が低く、又、熱膨張率がシリコンに近い
ものであり、そして機械的強度に富んでおり、ＬＳＩ素
子の実装に用いられる回路基板として好適なものであ
る。[Effect] The glass-mullite whisker composite substrate according to the present invention has a low dielectric constant, a thermal expansion coefficient close to that of silicon, and a high mechanical strength, and is a circuit used for mounting an LSI element. It is suitable as a substrate.
Claims (2)
ウィスカー５０〜５重量部とを含有することを特徴とす
るガラス・ムライトウィスカー複合基板。1. A glass-mullite whisker composite substrate comprising 50 to 95 parts by weight of glass powder and 50 to 5 parts by weight of mullite whiskers.
ウィスカー５０〜５重量部との混合物を焼成することを
特徴とするガラス・ムライトウィスカー複合基板の製造
方法。2. A method for producing a glass / mullite whisker composite substrate, which comprises firing a mixture of 50 to 95 parts by weight of glass powder and 50 to 5 parts by weight of mullite whiskers.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3271535A JPH05105508A (en) | 1991-10-18 | 1991-10-18 | Glass-mullite whisker composite board and its production |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3271535A JPH05105508A (en) | 1991-10-18 | 1991-10-18 | Glass-mullite whisker composite board and its production |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH05105508A true JPH05105508A (en) | 1993-04-27 |
Family
ID=17501422
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3271535A Pending JPH05105508A (en) | 1991-10-18 | 1991-10-18 | Glass-mullite whisker composite board and its production |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH05105508A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6544913B2 (en) * | 2001-01-19 | 2003-04-08 | Agency For Defense Development | Alumina-silica ceramic |
| US20130244914A1 (en) * | 2010-09-21 | 2013-09-19 | Oxane Materials, Inc. | Light Weight Proppant With Improved Strength And Methods Of Making Same |
| US9670763B2 (en) | 2010-01-29 | 2017-06-06 | Halliburton Energy Services, Inc. | Self-toughened high-strength proppant and methods of making same |
-
1991
- 1991-10-18 JP JP3271535A patent/JPH05105508A/en active Pending
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6544913B2 (en) * | 2001-01-19 | 2003-04-08 | Agency For Defense Development | Alumina-silica ceramic |
| US9670763B2 (en) | 2010-01-29 | 2017-06-06 | Halliburton Energy Services, Inc. | Self-toughened high-strength proppant and methods of making same |
| US20130244914A1 (en) * | 2010-09-21 | 2013-09-19 | Oxane Materials, Inc. | Light Weight Proppant With Improved Strength And Methods Of Making Same |
| US20150368548A1 (en) * | 2010-09-21 | 2015-12-24 | Halliburton Energy Services, Inc. | Light Weight Proppant With Improved Strength And Methods Of Making Same |
| US9796915B2 (en) * | 2010-09-21 | 2017-10-24 | Halliburton Energy Services, Inc. | Light weight proppant with improved strength and methods of making same |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JPS6115532B2 (en) | ||
| JPH0388762A (en) | Production of mullite-cordierite combined ceramics | |
| JPH05105508A (en) | Glass-mullite whisker composite board and its production | |
| JP4645935B2 (en) | Low-temperature fired porcelain composition and method for producing the same | |
| JP3021586B2 (en) | Method for producing low dielectric constant ceramic substrate and green sheet | |
| TW202112692A (en) | Glass powder, dielectric material, sintered body, and high frequency circuit member | |
| JPH02225339A (en) | Calcined body of glass ceramics | |
| US4792537A (en) | Dielectric ceramic composition for high frequencies | |
| JPH0643258B2 (en) | Dielectric material for circuit boards | |
| JPH10194846A (en) | Production of substrate fired at low temperature | |
| JP4202117B2 (en) | Low-frequency fired porcelain composition for high frequency and manufacturing method thereof | |
| JPH04114931A (en) | Production of sintered glass ceramic compact | |
| JP3164700B2 (en) | Glass ceramic substrate and method for manufacturing the same | |
| JPS6049149B2 (en) | Manufacturing method of white alumina/ceramic for electronic parts | |
| JP2003201169A (en) | Low temperature sintered type ceramic composition, low temperature fired ceramic board and production method therefor | |
| KR920005467B1 (en) | Composition of crystallized glass and preparation method thereof | |
| JPH0249265B2 (en) | ||
| JP2566183B2 (en) | Glass powder capable of producing a sintered glass ceramic containing hexagonal cordierite as the main crystal phase by crystallization | |
| JP3220359B2 (en) | High frequency dielectric ceramic composition and dielectric resonator | |
| JP2710311B2 (en) | Ceramic insulation material | |
| JP4047050B2 (en) | Low-temperature fired porcelain composition, low-temperature fired porcelain, and wiring board using the same | |
| JPH06100359A (en) | Production of ceramic sintering auxiliary and production of mullite ceramic using the same | |
| JPH0828126B2 (en) | Composite substrate and manufacturing method thereof | |
| JP3393774B2 (en) | Dielectric ceramic composition and dielectric resonator | |
| JPH08175864A (en) | Production of low-temperature sintered anorthite-gehlenite ceramic |