JPH0235702B2 - - Google Patents
Info
- Publication number
- JPH0235702B2 JPH0235702B2 JP63278550A JP27855088A JPH0235702B2 JP H0235702 B2 JPH0235702 B2 JP H0235702B2 JP 63278550 A JP63278550 A JP 63278550A JP 27855088 A JP27855088 A JP 27855088A JP H0235702 B2 JPH0235702 B2 JP H0235702B2
- Authority
- JP
- Japan
- Prior art keywords
- tetragonal
- plane
- temperature
- zirconium oxide
- crystal grains
- 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.)
- Expired - Lifetime
Links
- 239000013078 crystal Substances 0.000 claims description 69
- RKTYLMNFRDHKIL-UHFFFAOYSA-N copper;5,10,15,20-tetraphenylporphyrin-22,24-diide Chemical compound [Cu+2].C1=CC(C(=C2C=CC([N-]2)=C(C=2C=CC=CC=2)C=2C=CC(N=2)=C(C=2C=CC=CC=2)C2=CC=C3[N-]2)C=2C=CC=CC=2)=NC1=C3C1=CC=CC=C1 RKTYLMNFRDHKIL-UHFFFAOYSA-N 0.000 claims description 39
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 claims description 28
- 229910001928 zirconium oxide Inorganic materials 0.000 claims description 28
- 239000007784 solid electrolyte Substances 0.000 claims description 25
- 238000010304 firing Methods 0.000 claims description 13
- -1 yttrium compound Chemical class 0.000 claims description 11
- 238000004519 manufacturing process Methods 0.000 claims description 10
- 229910052727 yttrium Inorganic materials 0.000 claims description 10
- 238000002441 X-ray diffraction Methods 0.000 claims description 9
- 229910052573 porcelain Inorganic materials 0.000 description 31
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 26
- 239000002245 particle Substances 0.000 description 11
- 230000006866 deterioration Effects 0.000 description 10
- 229910052760 oxygen Inorganic materials 0.000 description 10
- 239000001301 oxygen Substances 0.000 description 10
- 239000012071 phase Substances 0.000 description 10
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 9
- 239000000203 mixture Substances 0.000 description 9
- 238000005452 bending Methods 0.000 description 8
- 238000001816 cooling Methods 0.000 description 8
- 238000010438 heat treatment Methods 0.000 description 8
- 238000000034 method Methods 0.000 description 7
- 238000005245 sintering Methods 0.000 description 6
- SIWVEOZUMHYXCS-UHFFFAOYSA-N oxo(oxoyttriooxy)yttrium Chemical compound O=[Y]O[Y]=O SIWVEOZUMHYXCS-UHFFFAOYSA-N 0.000 description 5
- 229910002077 partially stabilized zirconia Inorganic materials 0.000 description 5
- 239000002994 raw material Substances 0.000 description 5
- 230000032683 aging Effects 0.000 description 4
- 229910002078 fully stabilized zirconia Inorganic materials 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 3
- 238000000465 moulding Methods 0.000 description 3
- 238000013001 point bending Methods 0.000 description 3
- 239000000843 powder Substances 0.000 description 3
- 239000006104 solid solution Substances 0.000 description 3
- 239000003381 stabilizer Substances 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 230000006378 damage Effects 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 230000035939 shock Effects 0.000 description 2
- 239000007790 solid phase Substances 0.000 description 2
- 238000005979 thermal decomposition reaction Methods 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- OERNJTNJEZOPIA-UHFFFAOYSA-N zirconium nitrate Chemical compound [Zr+4].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O OERNJTNJEZOPIA-UHFFFAOYSA-N 0.000 description 2
- IVORCBKUUYGUOL-UHFFFAOYSA-N 1-ethynyl-2,4-dimethoxybenzene Chemical compound COC1=CC=C(C#C)C(OC)=C1 IVORCBKUUYGUOL-UHFFFAOYSA-N 0.000 description 1
- OBOSXEWFRARQPU-UHFFFAOYSA-N 2-n,2-n-dimethylpyridine-2,5-diamine Chemical compound CN(C)C1=CC=C(N)C=N1 OBOSXEWFRARQPU-UHFFFAOYSA-N 0.000 description 1
- NGDQQLAVJWUYSF-UHFFFAOYSA-N 4-methyl-2-phenyl-1,3-thiazole-5-sulfonyl chloride Chemical compound S1C(S(Cl)(=O)=O)=C(C)N=C1C1=CC=CC=C1 NGDQQLAVJWUYSF-UHFFFAOYSA-N 0.000 description 1
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 229910019714 Nb2O3 Inorganic materials 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 1
- 239000002250 absorbent Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000004927 clay Substances 0.000 description 1
- 229910052570 clay Inorganic materials 0.000 description 1
- 238000000975 co-precipitation Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000001125 extrusion Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 239000003779 heat-resistant material Substances 0.000 description 1
- 239000008240 homogeneous mixture Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 230000035882 stress Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 150000003748 yttrium compounds Chemical class 0.000 description 1
- 229910000347 yttrium sulfate Inorganic materials 0.000 description 1
- RTAYJOCWVUTQHB-UHFFFAOYSA-H yttrium(3+);trisulfate Chemical compound [Y+3].[Y+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O RTAYJOCWVUTQHB-UHFFFAOYSA-H 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
- 150000003755 zirconium compounds Chemical class 0.000 description 1
- DUNKXUFBGCUVQW-UHFFFAOYSA-J zirconium tetrachloride Chemical group Cl[Zr](Cl)(Cl)Cl DUNKXUFBGCUVQW-UHFFFAOYSA-J 0.000 description 1
- 229910021489 α-quartz Inorganic materials 0.000 description 1
Landscapes
- Compositions Of Oxide Ceramics (AREA)
- Conductive Materials (AREA)
Description
(産業上の利用分野)
本発明は高強度でかつ特定温度領域における長
時間使用による経時劣化の極めて少ないZrO2−
Y2O3系のジルコニア磁器であつて室温から約800
℃までの熱膨張曲線にヒステリシス現象のない固
体電解質およびその製造法に関するものである。
(従来の技術)
従来、酸素センサーなどの酸素濃淡電池を構成
する固体電解質に利用されているZrO2−Y2O3系
のジルコニア磁器の製造法としては、立方晶のみ
より成る完全安定化ジルコニア磁器の製造法と、
立方晶と単斜晶より成る部分安定化ジルコニア磁
器の製造法が知られており、これらの製造法によ
つて得られるジルコニア磁器はいずれも耐熱材
料、固体電解質等として使用されている。
(発明が解決しようとする課題)
このうち完全安定化ジルコニア磁器は、常温か
ら約1500℃迄の温度範囲において安定であり長時
間使用による経時劣化もほとんど無いものである
が、反面強度が低いので例えば自動車排ガス中の
酸素濃度を検出する酸素センサー用固体電解質と
して利用した場合、熱衝撃によつて極めて破損し
やすいという欠点があつた。一方立方晶と単斜晶
よりなる部分安定化ジルコニア磁器は完全安定化
ジルコニア磁器に較べると強度は大きく耐熱衝撃
性もよいものであるが、200℃ないし300℃という
特定温度域における強度の経時劣化が極めて大き
く、該温度で長時間使用した場合、磁器表面に微
細なクラツクが多数発生して吸水性を示すように
なり著しく強度が低下し、ついには破損するとい
う重大な欠点を有しているものであつた。
(課題を解決するための手段)
これはZrO2−Y2O3系部分安定化ジルコニア磁
器では約1500℃の焼成温度において正方晶である
結晶粒子が約1500℃から室温への冷却中に500℃
付近で単斜晶に相変態を起こし、その際生ずる体
積変化により磁器中に過大な応力が加わりそのた
め極めて微小なクラツクが結晶粒子内に多数発生
し、このクラツクが200℃ないし300℃の特定温度
領域に長時間おかれると拡大し、やがて磁器破壊
に至るものであると考えられる。
さらに、立方晶と単斜晶より成る部分安定化ジ
ルコニア磁器は室温から約800℃の間て加熱冷却
を繰り返すと500℃付近で起こる単斜晶と正方晶
との相変態により熱膨張曲線が加熱方向と冷却方
向で異なるいわゆるヒステリシス曲線となり、か
つ室温にもどしたときの寸法が加熱冷却の前後で
異なるので高精度の寸法が維持できない欠点があ
つた。
本発明は、従来のこのような酸素濃淡電池に用
いる固体電解質としての部分安定化ジルコニア磁
器の欠点を解消し、優れた強度を有するとともに
200℃ないし300℃の特定温度域における強度の経
時劣化を著しく改良した主としてZrO2とY2O3よ
り成りY2O3/ZrO2のモル比が2/98〜7/93の
範囲であつて結晶粒子が主として正方晶または正
方晶と立方晶の結晶粒子よりなり、正方晶の
(200)面、立方晶の(200)面および単斜晶の
(111)面の各々のX線回折線のピーク強度をT
200,C200およびM111としたとき次式
1≧T(200)+C(200)/T(200)+C(200)+
M(111)≧0.72
が成立し、かつ平均結晶粒径が2μ以下で、室温
から高温までの熱膨張曲線にヒステリシス現象の
ないことを特徴とする固体電解質及びその製造法
であり、結晶子径が1000Å以下の酸化ジルコニウ
ムまたは無定形酸化ジルコニウム特に好ましく
は、水酸化ジルコニウムを熱分解して得た酸化ジ
ルコニウムとイツトリウム化合物より成り
Y2O3/ZrO2のモル比が2/98〜7/93の範囲で
ある混合物の成形体、好ましくはその混合物を
200〜1200℃の温度範囲内で熱分解し、解砕した
後成形した成形体を、1000〜1550℃の温度範囲で
焼成して、主として正方晶の結晶粒子、または正
方晶の結晶粒子と立方晶の結晶粒子とより成り、
正方晶の(200)面、立方晶の(200)面および単
斜晶の(111)面の各々のX線回折線のピーク強
度をT200,C200およびM111としたと
き次式
1≧T(200)+C(200)/T(200)+C(200)+
M(111)≧0.72
が成立し、かつ平均結晶粒子径が2μ以下で、室
温から高温までの熱膨張曲線にヒステリシス現象
のない固体電解質の製造法である。
すなわち、本発明は200〜300℃の特定温度域に
おける強度の経時劣化が極めて少なく、かつ室温
〜800℃の温度域での加熱冷却による寸法変化の
ないジルコニア磁器からなる固体電解質として
は、Y2O3/ZrO2のモル比が2/98〜7/93であ
り、各々の結晶粒子の結晶相が主として正方晶の
結晶粒子、または正方晶の結晶粒子と立方晶の結
晶粒子とより成り、かつ平均結晶粒子径が2μ以
下である、すなわちY2O3/ZrO2モル比、結晶粒
子の結晶相、平均結晶粒子径という3要件のいず
れも満たすことが大切であることを究明し、その
ためには成形体を構成する酸化ジルコニウムの結
晶子径が特定粒径以下または無定形であることが
最も重要であるとともに、安定化剤の量および焼
成温度等が特定範囲内であることが必要であるこ
とを幾多の研究の結果究明したことにもとづくも
のである。
本発明を以下に詳しく説明する。
本発明において200℃ないし300℃における耐久
性にすぐれていると称するのは、200℃ないし300
℃の間の任意の温度において経時劣化が少ないこ
とを意味する。具体的な測定手段の一例としては
実施例で述べるように大気中で200℃ないし300℃
の間を10℃/分の昇降温速度で加熱冷却を繰り返
す耐久試験を行い、耐久前と耐久後の抗折強度の
変化を測定するのが良い。耐久時間は長い程劣化
の程度が増大するが、1500時間程度では従来の固
体電解質として用いられてきたジルコニア磁器と
本発明によつて得られるジルコニア磁器との差が
明瞭となる。
焼結後のジルコニア磁器より成る固体電解質
が、主として正方晶の結晶粒子、または正方晶の
結晶粒子と立方晶の結晶粒子とより安定的に成る
ためには、前述のとおり成形体を構成する酸化ジ
ルコニウムは特定結晶子径すなわち1000Å以下又
は無定形、好ましくは結晶子径が700Å〜300Åで
あることがよい。
すなわち成形体を構成する酸化ジルコニウムの
結晶子径とジルコニア磁器の結晶相との関係をX
線回折強度比で表わすと、例えば第1図および第
2図に示すとおり、結晶子径が700Å以下の範囲
又は無定形では主として正方晶の結晶粒子(H領
域)または正方晶の結晶粒子と立方晶の結晶粒子
(H′領域)とより成つており、700〜1000Åの範
囲ではこれらにわずかに単斜晶の結晶粒子が混入
する程度(I領域)であるが1000Åを超えると急
激に単斜晶の結晶粒子が増加する(J領域)。
なお、結晶子径が0μとは無定形の酸化ジルコ
ニウムであることを示す。ただし無定形の酸化ジ
ルコニウムを用いる場合は焼成収縮が過大となる
ため、好ましくは結晶の酸化ジルコニウムがよ
い。ここで第1図および第2図中、T200,C
200,M111はそれぞれ正方晶の(200)面、
立方晶の(200)面、単斜晶の(111)面のX線
回折線強度を示す。
従つて、ジルコニア磁器からなる固体電解質の
結晶相を経時劣化の少ない主として正方晶の結晶
粒子、または正方晶の結晶粒子と立方晶の結晶粒
子とに安定的に維持するためには、成形体を構成
する酸化ジルコニウムは結晶子径が1000Å以下ま
たは無定形でなければならないことが第1図およ
び第2図よりも明確である。ここで重要なことは
特定の結晶子径をもつ酸化ジルコニウムは酸化イ
ツトリウム等の安定化剤と固溶していないことで
ある。固溶していない原料を用いると焼成時に酸
化ジルコニウムと安定化剤が反応焼結を起こす。
原料の段階で固溶していると単なる固相焼結とな
る。特に本発明の固体電解質の場合、反応焼結を
起こすと固相焼結より焼成温度を下げることがで
き、磁器の粒成長を抑制し、結果としてより正方
晶の結晶粒子が安定し、200℃〜300℃での耐久性
が良好となる。ここで、原料調製時に例えばジル
コニウム化合物とイツトリウム化合物との混合溶
液から共沈によつて酸化ジルコニウムと酸化イツ
トリウムとした原料であつても、酸化ジルコニウ
ムと酸化イツトリウムが固溶していなければ差し
支えない。
なお、結晶子径が1000Å以下または無定形の酸
化ジルコニウムは塩化ジルコニウム、硝酸ジルコ
ニウム等の熱分解等でも得られるが、好ましくは
水酸化ジルコニル(ZrO(OH)2・nH2O)を200〜
1100℃の温度より好ましくは500〜1050℃の温度
で熱分解した酸化ジルコニウム粉末がよい。この
場合水酸化ジルコニルの熱分解温度が200℃未満
では水酸化ジルコニル中の水が完全に取れず、ま
た1100℃を越えると結晶子径は1000Åを超えるの
で好ましくない。
本発明の製造法においてはまず、酸化ジルコニ
ウムとイツトリウム化合物をY2O3/ZrO2のモル
比が2/98〜7/93の範囲内となるように混合す
る。この場合酸化ジルコニウムとイツトリウム化
合物との混合比がY2O3/ZrO2のモル比に換算し
て2/98〜7/93の範囲内であることが、経時劣
化改善のために極めて重要である。これは2/98
未満では経時劣化改善のための正方晶の結晶粒子
の生成が無く、また7/93を越えても正方晶の結
晶粒子をほとんど含まれなくなり立方晶の結晶粒
子のジルコニア磁器となるからである。
また、イツトリウム化合物としては酸化イツリ
ウム、塩化イツトリウム、硝酸イツトリウム、硫
酸イツトリウム等が好ましく、この場合イツトリ
ウム化合物としては、酸化物に換算して約30モル
%以下の例えばYb2O3、Sc2O3、Nb2O3、
Sm2O3、CeO2等の希土類元素酸化物あるいは
CaO、MgO等で置換したものでもよい。次いで、
混合物をラバープレス成形、押出成形、鋳込成形
等の成形法により所定の形状に成形し、空気中で
1000〜1550℃の温度範囲内で焼成する。焼成は
1000〜1550℃の温度好ましくは1100〜1450℃の温
度範囲内で最高温度で1〜20時間保持する。焼成
時間は一般に低温焼成のときほど長くする方がよ
い。なお、焼成温度と磁器の結晶相との関係は、
焼成温度が1000℃未満あるいは1550℃を越えると
急激に単斜晶の生成が増大するので好ましくな
く、1000〜1550℃の温度範囲内であれば主として
正方晶または正方晶と立方晶の混合相が安定的に
生成する。更にY2O3/ZrO2のモル比が好ましく
は4/96〜7/93の範囲では主として正方晶と立
方晶より成る磁器が得られ、酸素イオン導電性が
高く200〜300℃における経時劣化が少ない固体電
解質となる。
なお、酸化ジルコニウムとイツトリウム化合物
との混合物を200〜1200℃の温度で1〜10時間程
度加熱することによりイツトリウム化合物を熱分
解して、さらに必要に応じてボールミル等で解砕
したものを原料として使用すると酸化ジルコニウ
ムと酸化イツトリウムの均一な混合物が得られ、
これを形成し焼成するとより緻密な磁器ができ好
ましいものである。ボールミル等による解砕後の
原料粒度は0.1〜10μ程度である。
また、酸化ジルコニウムとイツトリウム化合物
の混合物に焼結助剤としてSiO2、Al2O3、粘土等
を磁器全体の30重量%以下で添加してもよい、
なお、本発明において酸化ジルコニウムの結晶
子径はCuKα線を用いたX線回折法で行い、式D
=0.89λ/(B−b)cosθにより求めた。ここで
Dは求める酸化ジルコニウムの結晶子径、λは
CuKα線の波長で1.541Å、Bは酸化ジルコニウム
の単斜晶(111)面または正方晶(111)面の回
折線の半減値幅(ラジアン)のうち大きい方の
値、bは内部標準として添加する結晶子径の3000
Å以上のα−石英の(101)面の半減値幅(ラジ
アン)、θは酸化ジルコニウムの半減値幅の測定
に用いた回折線の回折角2θの1/2の値である。
抗折強度は通常に行われている3点曲げ法ある
いは4点曲げ法によるが、初期の測定と200℃な
いし300℃の温度域に曝した後の測定とは同一方
法によるものであり、所定のテストピース形状に
した後、200℃ないし300℃の温度域に曝すもので
ある。
次に実施例を述べる。
第1表に示すように酸化ジルコニウムとイツト
リウム化合物を表中の組成となるようにボールミ
ル混合した。そしてその混合物を表中に熱分解の
記載のあるものはその条件で熱分解を行つてから
焼結助剤を加えてボールミルにて湿式粉砕し、乾
燥した後それぞれの粉末をプレス成形し、第1表
記載の温度条件で焼成した。そして得られた磁器
について平均結晶粒子径およびX線回折線による
正方晶、立方晶、単斜晶の強度比および抗折強度
を測定した。なお結晶子径は成形体とする混合物
を用いて測定し、磁器のX線回折線強度比の測定
は磁器の鏡面研磨面を用いて行い立方晶の(200)
面、正方晶の(200)面および単斜晶の(111)面
でのX線回折線ピーク強度の比を求めた。また抗
折強度は3.5×3.5×50mmの棒状に仕上げ3点曲げ
法にて求めた。また第1表中の耐久試験とは200
〜300℃の間を10℃/分の昇降温速度で加熱、冷
却を繰り返した耐久試験であり、1500時間経過
後、抗折強度を測定した。さらに耐久試験前の抗
折強度に対する耐久試験後の抗折強度の割合をパ
ーセントで示した。
なお第1表には本発明の数値限定範囲外の例を
参考例として合わせ記載した。
(Industrial Application Field) The present invention is a ZrO 2
Y 2 O 3 series zirconia porcelain with temperature range from room temperature to approximately 800
The present invention relates to a solid electrolyte with no hysteresis phenomenon in its thermal expansion curve up to ℃, and a method for producing the same. (Prior art) Conventionally, the manufacturing method for ZrO 2 −Y 2 O 3 -based zirconia porcelain, which is used as a solid electrolyte for oxygen concentration batteries such as oxygen sensors, is to produce fully stabilized zirconia consisting only of cubic crystals. porcelain manufacturing method,
Methods for producing partially stabilized zirconia porcelain composed of cubic crystals and monoclinic crystals are known, and zirconia porcelains obtained by these production methods are all used as heat-resistant materials, solid electrolytes, and the like. (Problem to be solved by the invention) Of these, fully stabilized zirconia porcelain is stable in the temperature range from room temperature to approximately 1500°C and hardly deteriorates over time due to long-term use, but on the other hand, it has low strength. For example, when used as a solid electrolyte for an oxygen sensor that detects the oxygen concentration in automobile exhaust gas, it has the disadvantage of being extremely susceptible to damage due to thermal shock. On the other hand, partially stabilized zirconia porcelain made of cubic and monoclinic crystals has higher strength and better thermal shock resistance than fully stabilized zirconia porcelain, but its strength deteriorates over time in a specific temperature range of 200°C to 300°C. is extremely large, and when used for a long time at such temperatures, it has the serious drawback that many minute cracks occur on the porcelain surface, it becomes water-absorbent, its strength decreases significantly, and it eventually breaks. It was hot. (Means for solving the problem) This means that in ZrO 2 −Y 2 O 3 system partially stabilized zirconia porcelain, the crystal grains, which are tetragonal at a firing temperature of about 1500°C, change to 500°C during cooling from about 1500°C to room temperature. ℃
A phase transformation to monoclinic occurs in the vicinity, and the volume change that occurs at this time applies excessive stress to the porcelain, resulting in many extremely small cracks within the crystal grains, and these cracks occur at a specific temperature of 200°C to 300°C. It is thought that if left in the area for a long time, it will expand and eventually lead to porcelain destruction. Furthermore, when partially stabilized zirconia porcelain consisting of cubic and monoclinic crystals is repeatedly heated and cooled from room temperature to approximately 800°C, the thermal expansion curve becomes heated due to phase transformation between monoclinic and tetragonal crystals that occurs around 500°C. The so-called hysteresis curves are different in the direction and the cooling direction, and the dimensions when returned to room temperature are different before and after heating and cooling, so there is a drawback that highly accurate dimensions cannot be maintained. The present invention eliminates the drawbacks of partially stabilized zirconia porcelain as a solid electrolyte used in conventional oxygen concentration batteries, and has excellent strength and
It is mainly composed of ZrO 2 and Y 2 O 3 and the molar ratio of Y 2 O 3 /ZrO 2 is in the range of 2/98 to 7/93 and has significantly improved the aging deterioration of strength in a specific temperature range of 200℃ to 300℃. The crystal grains are mainly composed of tetragonal or tetragonal and cubic crystal grains, and the X-ray diffraction lines of each of the tetragonal (200) plane, the cubic (200) plane, and the monoclinic (111) plane The peak intensity of T
200, C200 and M111, the following formula 1≧T(200)+C(200)/T(200)+C(200)+
A solid electrolyte and its manufacturing method characterized by satisfying M(111)≧0.72, having an average crystal grain size of 2μ or less, and having no hysteresis phenomenon in its thermal expansion curve from room temperature to high temperature. Zirconium oxide or amorphous zirconium oxide having a diameter of 1000 Å or less, particularly preferably a zirconium oxide and yttrium compound obtained by thermally decomposing zirconium hydroxide.
A molded article of a mixture in which the molar ratio of Y 2 O 3 /ZrO 2 is in the range of 2/98 to 7/93, preferably the mixture.
The molded body is thermally decomposed in a temperature range of 200 to 1200℃, crushed, and then molded, and then fired in a temperature range of 1000 to 1550℃ to form mainly tetragonal crystal particles or tetragonal crystal particles and cubic Consisting of crystal grains,
When the peak intensities of the X-ray diffraction lines of the (200) plane of the tetragonal crystal, the (200) plane of the cubic crystal, and the (111) plane of the monoclinic crystal are respectively T200, C200, and M111, the following formula 1≧T(200 )+C(200)/T(200)+C(200)+
This is a method for producing a solid electrolyte that satisfies M(111)≧0.72, has an average crystal grain size of 2 μ or less, and has no hysteresis phenomenon in its thermal expansion curve from room temperature to high temperature. That is, the present invention uses Y 2 as a solid electrolyte made of zirconia porcelain that has very little deterioration in strength over time in a specific temperature range of 200 to 300°C and that does not change in size due to heating and cooling in a temperature range of room temperature to 800°C. The molar ratio of O 3 /ZrO 2 is 2/98 to 7/93, and the crystal phase of each crystal particle is mainly composed of tetragonal crystal particles, or tetragonal crystal particles and cubic crystal particles, We also determined that it is important that the average crystal grain size is 2μ or less, that is, the Y 2 O 3 /ZrO 2 molar ratio, the crystal phase of the crystal grains, and the average crystal grain size. It is most important that the crystallite size of the zirconium oxide constituting the molded body be below a certain particle size or be amorphous, and that the amount of stabilizer and firing temperature etc. be within a certain range. It is based on something that has been discovered as a result of numerous studies. The invention will be explained in detail below. In the present invention, "having excellent durability at 200℃ to 300℃" means
This means that there is little deterioration over time at any temperature between ℃. As an example of a specific measurement method, as described in the examples, 200℃ to 300℃ in the atmosphere
It is best to conduct a durability test in which heating and cooling are repeated at a rate of temperature rise and fall of 10°C/min, and to measure the change in bending strength before and after durability. The longer the durability time, the greater the degree of deterioration, but after about 1500 hours, the difference between the zirconia porcelain that has been used as a conventional solid electrolyte and the zirconia porcelain obtained by the present invention becomes clear. In order for the solid electrolyte made of zirconia porcelain after sintering to be more stable with mainly tetragonal crystal grains, or tetragonal crystal grains and cubic crystal grains, the oxidation that constitutes the molded body must be Zirconium preferably has a specific crystallite diameter of 1000 Å or less or is amorphous, preferably a crystallite diameter of 700 Å to 300 Å. In other words, the relationship between the crystallite diameter of zirconium oxide constituting the molded body and the crystal phase of zirconia porcelain is expressed as
Expressed in terms of line diffraction intensity ratio, for example, as shown in Figures 1 and 2, in the range where the crystallite diameter is 700 Å or less or in the amorphous form, there are mainly tetragonal crystal grains (H region) or tetragonal crystal grains and cubic crystal grains. In the range of 700 to 1000 Å, there are only a few monoclinic crystal grains mixed in (I region), but beyond 1000 Å, the monoclinic crystal grains suddenly become monoclinic. The number of crystal grains increases (J region). Note that a crystallite diameter of 0 μ indicates that it is amorphous zirconium oxide. However, if amorphous zirconium oxide is used, the firing shrinkage will be excessive, so crystalline zirconium oxide is preferable. Here, in FIGS. 1 and 2, T200, C
200 and M111 are tetragonal (200) planes, respectively.
Shows the X-ray diffraction line intensities of the cubic (200) plane and the monoclinic (111) plane. Therefore, in order to stably maintain the crystal phase of a solid electrolyte made of zirconia porcelain into mainly tetragonal crystal grains or tetragonal crystal grains and cubic crystal grains with little deterioration over time, it is necessary to form a compact. It is clearer from FIGS. 1 and 2 that the constituting zirconium oxide must have a crystallite diameter of 1000 Å or less or be amorphous. What is important here is that zirconium oxide having a specific crystallite diameter is not dissolved in solid solution with a stabilizer such as yttrium oxide. If a raw material that is not in solid solution is used, zirconium oxide and the stabilizer will react and sinter during firing.
If solid solution is present at the raw material stage, it will simply be solid phase sintering. In particular, in the case of the solid electrolyte of the present invention, when reaction sintering occurs, the firing temperature can be lowered than that of solid phase sintering, suppressing the grain growth of porcelain, resulting in more stable tetragonal crystal grains, and increasing the temperature at 200°C. Good durability at ~300°C. Here, even if the raw material is made into zirconium oxide and yttrium oxide by coprecipitation from a mixed solution of a zirconium compound and a yttrium compound during raw material preparation, there is no problem as long as the zirconium oxide and yttrium oxide are not solidly dissolved. Note that zirconium oxide with a crystallite diameter of 1000 Å or less or amorphous can be obtained by thermal decomposition of zirconium chloride, zirconium nitrate, etc., but preferably zirconyl hydroxide (ZrO(OH) 2 · nH 2 O) is
Zirconium oxide powder thermally decomposed at a temperature of 500 to 1050°C is preferable than 1100°C. In this case, if the thermal decomposition temperature of zirconyl hydroxide is less than 200°C, water in the zirconyl hydroxide cannot be completely removed, and if it exceeds 1100°C, the crystallite diameter will exceed 1000 Å, which is not preferable. In the production method of the present invention, first, zirconium oxide and a yttrium compound are mixed such that the molar ratio of Y 2 O 3 /ZrO 2 falls within the range of 2/98 to 7/93. In this case, it is extremely important for the mixing ratio of zirconium oxide and yttrium compound to be within the range of 2/98 to 7/93 in terms of Y 2 O 3 /ZrO 2 molar ratio to improve aging deterioration. be. This is 2/98
If it is less than 7/93, tetragonal crystal grains will not be produced to improve aging deterioration, and if it exceeds 7/93, it will contain almost no tetragonal crystal grains, resulting in zirconia porcelain with cubic crystal grains. In addition, the yttrium compound is preferably yttrium oxide, yttrium chloride, yttrium nitrate, yttrium sulfate, etc. In this case, the yttrium compound is about 30 mol% or less in terms of oxide, such as Yb 2 O 3 , Sc 2 O 3 , Nb2O3 ,
Rare earth element oxides such as Sm 2 O 3 and CeO 2 or
It may also be substituted with CaO, MgO, etc. Then,
The mixture is molded into a predetermined shape using a molding method such as rubber press molding, extrusion molding, or casting molding, and then heated in air.
Fire within the temperature range of 1000-1550℃. Firing is
The temperature is maintained at a maximum temperature of 1000 to 1550°C, preferably 1100 to 1450°C, for 1 to 20 hours. Generally, it is better to make the firing time longer when firing at a lower temperature. The relationship between firing temperature and crystal phase of porcelain is as follows:
If the firing temperature is less than 1,000℃ or exceeds 1,550℃, the formation of monoclinic crystals will increase rapidly, which is undesirable.If the temperature is within the temperature range of 1,000 to 1,550℃, the firing temperature will mainly be tetragonal or a mixed phase of tetragonal and cubic crystals. Generate stably. Furthermore, when the molar ratio of Y 2 O 3 /ZrO 2 is preferably in the range of 4/96 to 7/93, a porcelain mainly composed of tetragonal and cubic crystals is obtained, which has high oxygen ion conductivity and resists aging at 200 to 300°C. becomes a solid electrolyte with less In addition, the yttrium compound is thermally decomposed by heating a mixture of zirconium oxide and a yttrium compound at a temperature of 200 to 1,200 degrees Celsius for about 1 to 10 hours, and if necessary, the material is crushed using a ball mill etc. When used, a homogeneous mixture of zirconium oxide and yttrium oxide is obtained,
When this is formed and fired, a finer porcelain can be produced, which is preferable. The particle size of the raw material after crushing using a ball mill or the like is approximately 0.1 to 10μ. Furthermore, SiO 2 , Al 2 O 3 , clay, etc. may be added as a sintering aid to the mixture of zirconium oxide and yttrium compound in an amount of 30% by weight or less of the total weight of the porcelain. The diameter was determined by X-ray diffraction method using CuKα rays, and the formula D
It was determined by =0.89λ/(B-b)cosθ. Here, D is the desired crystallite diameter of zirconium oxide, and λ is
The wavelength of the CuKα ray is 1.541 Å, B is the larger value of the half-value width (in radians) of the diffraction line of the monoclinic (111) plane or the tetragonal (111) plane of zirconium oxide, and b is added as an internal standard. Crystallite diameter of 3000
The half-life width (in radians) of the (101) plane of α-quartz of Å or more, θ is the value of 1/2 of the diffraction angle 2θ of the diffraction line used to measure the half-life width of zirconium oxide. The bending strength is determined by the commonly used three-point bending method or four-point bending method, but the initial measurement and the measurement after exposure to a temperature range of 200°C to 300°C are performed using the same method. After forming into a test piece shape, the test piece is exposed to a temperature range of 200℃ to 300℃. Next, an example will be described. As shown in Table 1, zirconium oxide and yttrium compounds were mixed in a ball mill to have the compositions shown in the table. Then, if the mixture is listed as thermally decomposed in the table, it is thermally decomposed under the conditions specified, a sintering aid is added, the mixture is wet-pulverized in a ball mill, and after drying, each powder is press-molded. It was fired under the temperature conditions listed in Table 1. The resulting porcelain was measured for its average crystal grain size, the intensity ratio of tetragonal, cubic, and monoclinic crystals by X-ray diffraction, and the bending strength. The crystallite diameter was measured using the mixture used as a compact, and the X-ray diffraction line intensity ratio of the porcelain was measured using the mirror-polished surface of the porcelain.
The ratio of the X-ray diffraction line peak intensities on the (200) plane of the tetragonal crystal and the (111) plane of the monoclinic crystal was determined. Moreover, the bending strength was determined by the three-point bending method after finishing a rod shape of 3.5 x 3.5 x 50 mm. Also, the durability test in Table 1 is 200
This was a durability test in which heating and cooling were repeated between ~300°C and a heating/cooling rate of 10°C/min, and the bending strength was measured after 1500 hours had elapsed. Furthermore, the ratio of the bending strength after the durability test to the bending strength before the durability test is shown in percentage. Note that Table 1 also lists examples outside the numerically limited range of the present invention as reference examples.
【表】【table】
【表】【table】
【表】【table】
【表】
第1表からも明らかなとおり本発明の製造法に
よるジルコニア磁器よりなる固体電解質は、主と
して正方晶の結晶粒子または正方晶の結晶粒子と
立方晶の結晶粒子とより成り、平均結晶粒子径が
2μ以下の極めて高強度で、かつ200〜300℃にお
ける耐久試験後の耐久試験前に対する抗折強度の
変化がいずれも80%以上という経時劣化の少ない
固体電解質であることが確認された。
また第1表に示される本発明のいずれの固体電
解質も、第3図に示されるように低温から高温ま
での熱膨張曲線はほぼ線型となりヒステリシス現
象のないものとなつた。
以上述べたとおり、本発明は200〜300℃の特定
温度域における経時劣化が極めて少なく、室温か
ら高温度域までの熱膨張曲線にヒステリシス現象
のないジルコニア磁器より成る固体電解質として
はY2O3/ZrO2モル比が2/98〜7/93において
結晶相が主として正方晶の結晶粒子または正方晶
の結晶粒子と立方晶の結晶粒子とより成りかつ平
均結晶粒子径が2μ以下であることが大切である
ことを見出し、そのためには成形体を構成する酸
化ジルコニウムが結晶子径1000Å以下または無定
形でY2O3/ZrO2モル比が2/98〜7/93でかつ
焼成温度が1000〜1550℃でなければならないこと
を究明したものであり、本発明の製造法により特
定温度域での経時劣化が少なく熱処理による寸法
変化がない機械的強度が強いジルコニア固体電解
質が得られるので、この固体電解質は、自動車用
酸素センサ、鉄鋼用酸素メータ、計測用酸素ポン
プあるいは固体電解質燃料電池などの酸素濃淡電
池用固体電解質としてあるいはサーミスタとして
利用でき産業上極めて有用なものとなる。[Table] As is clear from Table 1, the solid electrolyte made of zirconia porcelain produced by the production method of the present invention mainly consists of tetragonal crystal particles or tetragonal crystal particles and cubic crystal particles, and the average crystal grain The diameter is
It was confirmed that the solid electrolyte has an extremely high strength of 2μ or less, and shows a change in bending strength of 80% or more after the durability test at 200 to 300°C compared to before the durability test, which shows little deterioration over time. Furthermore, in all of the solid electrolytes of the present invention shown in Table 1, the thermal expansion curve from low temperature to high temperature was almost linear, and there was no hysteresis phenomenon, as shown in FIG. As described above, the present invention has very little deterioration over time in a specific temperature range of 200 to 300°C, and Y 2 O 3 is a solid electrolyte made of zirconia porcelain that has no hysteresis phenomenon in its thermal expansion curve from room temperature to high temperature. /ZrO 2 molar ratio of 2/98 to 7/93, the crystal phase is mainly composed of tetragonal crystal grains or tetragonal crystal grains and cubic crystal grains, and the average crystal grain size is 2 μ or less. In order to achieve this, the zirconium oxide constituting the compact must have a crystallite diameter of 1000 Å or less, be amorphous, have a Y 2 O 3 /ZrO 2 molar ratio of 2/98 to 7/93, and have a firing temperature of 1000 Å. It was determined that the temperature must be ~1550℃, and the manufacturing method of the present invention can produce a zirconia solid electrolyte with strong mechanical strength that exhibits little deterioration over time in a specific temperature range and no dimensional change due to heat treatment. Solid electrolytes can be used as solid electrolytes for automobile oxygen sensors, iron and steel oxygen meters, measuring oxygen pumps, oxygen concentration batteries such as solid electrolyte fuel cells, or as thermistors, making them extremely useful in industry.
第1図および第2図は酸化ジルコニウム粉末の
結晶子径と磁器の結晶相との関係を示す説明図で
あり、第3図は本発明の固体電解質の加熱と冷却
の際の熱膨張曲線を示す図である。
Figures 1 and 2 are explanatory diagrams showing the relationship between the crystallite diameter of zirconium oxide powder and the crystalline phase of porcelain, and Figure 3 shows the thermal expansion curve during heating and cooling of the solid electrolyte of the present invention. FIG.
Claims (1)
ZrO2のモル比が2/98〜7/93の範囲であつて、
主として正方晶の結晶粒子、または正方晶の結晶
粒子と立方晶の結晶粒子よりなり、かつ平均結晶
粒径が2μ以下であつて、 正方晶の(200)面、立方晶の(200)面および
単斜晶の(111)面の各々のX線回折線のピーク
強度をT200,C200およびM111とした
とき次式 1≧T(200)+C(200)/T(200)+C(200)+
M(111)≧0.72 が成立し、室温から高温までの熱膨張曲線にヒス
テリシス現象のないことを特徴とする固体電解
質。 2 結晶子径が1000Å以下の酸化ジルコニウムま
たは無定形の酸化ジルコニウムとイツトリウム化
合物より成り、Y2O3/ZrO2のモル比が2/98〜
7/93の範囲である混合物の成形体を1000〜1550
℃の温度範囲で焼成して、主として正方晶の結晶
粒子、または正方晶の結晶粒子と立方晶の結晶粒
子とよりなり、かつ、平均結晶粒子径が2μ以下
で、正方晶の(200)面、立方晶の(200)面およ
び単斜晶の(111)面の各々のX線回折線のピー
ク強度をT200,C200およびM111とし
たとき次式 1≧T(200)+C(200)/T(200)+C(200)+
M(111)≧0.72 が成立し、室温から高温までの熱膨張曲線にヒス
テリシス現象のない固体電解質を製造することを
特徴とする固体電解質の製造法。[Claims] 1 Mainly composed of ZrO 2 and Y 2 O 3 , Y 2 O 3 /
The molar ratio of ZrO 2 is in the range of 2/98 to 7/93,
It is mainly composed of tetragonal crystal grains, or tetragonal crystal grains and cubic crystal grains, and has an average crystal grain size of 2 μ or less, and has a tetragonal (200) plane, a cubic (200) plane, and a cubic crystal grain. When the peak intensity of each X-ray diffraction line of the monoclinic (111) plane is T200, C200 and M111, the following formula 1≧T(200)+C(200)/T(200)+C(200)+
A solid electrolyte that satisfies M(111)≧0.72 and has no hysteresis phenomenon in its thermal expansion curve from room temperature to high temperature. 2 Consisting of zirconium oxide or amorphous zirconium oxide and yttrium compound with a crystallite diameter of 1000 Å or less, and a molar ratio of Y 2 O 3 /ZrO 2 of 2/98 ~
7/93 range of 1000 to 1550
By firing at a temperature range of , when the peak intensities of the X-ray diffraction lines of the (200) plane of the cubic crystal and the (111) plane of the monoclinic crystal are respectively T200, C200 and M111, the following formula 1≧T(200)+C(200)/T (200)+C(200)+
A method for producing a solid electrolyte, characterized by producing a solid electrolyte that satisfies M(111)≧0.72 and has no hysteresis phenomenon in its thermal expansion curve from room temperature to high temperature.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP63278550A JPH01261267A (en) | 1988-11-05 | 1988-11-05 | Solid electrolyte and its production |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP63278550A JPH01261267A (en) | 1988-11-05 | 1988-11-05 | Solid electrolyte and its production |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP56020833A Division JPS57140375A (en) | 1980-03-26 | 1981-02-17 | Ceramic manufacture |
Publications (2)
Publication Number | Publication Date |
---|---|
JPH01261267A JPH01261267A (en) | 1989-10-18 |
JPH0235702B2 true JPH0235702B2 (en) | 1990-08-13 |
Family
ID=17598823
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JP63278550A Granted JPH01261267A (en) | 1988-11-05 | 1988-11-05 | Solid electrolyte and its production |
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JP (1) | JPH01261267A (en) |
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US5968673A (en) * | 1994-03-18 | 1999-10-19 | Toto Ltd. | Solid electrolyte thin film and method for producing the same |
JPH11316211A (en) * | 1998-03-05 | 1999-11-16 | Denso Corp | Laminated air/fuel ratio sensor element |
US6174489B1 (en) | 1995-09-01 | 2001-01-16 | Denso Corporation | Method for manufacturing a gas sensor unit |
KR101608293B1 (en) * | 2009-10-28 | 2016-04-01 | 쿄세라 코포레이션 | Fuel cell, cell stack, fuel cell module, and fuel cell device |
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1988
- 1988-11-05 JP JP63278550A patent/JPH01261267A/en active Granted
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