JP2007332026A - Zirconia sintered compact - Google Patents
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本発明は、光コネクター部品，精密加工部品及び粉砕機用部材等の構造用セラミックスの原料に用いられる、とくに成形性がよく、低温焼結性にも優れた新規ジルコニア微粉末及びそのジルコニア微粉末をスラリーにして噴霧造粒して得られるジルコニア顆粒並びにその製造方法に関するものである。 The present invention relates to a novel zirconia fine powder that is used as a raw material for structural ceramics such as optical connector parts, precision processed parts, and pulverizer members, and has excellent moldability and excellent low-temperature sinterability, and the zirconia fine powder. The present invention relates to a zirconia granule obtained by making a slurry into a spray granulation and a method for producing the same.
ジルコニアセラミックスは、高強度，高靭性を発現するため、光コネクター部品，精密加工部品，粉砕メディア，粉砕機用部剤，刃物等の幅広い用途で使用されている。しかしながら、このような高強度・高靭性を有するジルコニアセラミックスは、空気中，２００〜３００℃の温度で長時間曝されると、準安定相である正方晶が安定相の単斜晶へ約４％の体積膨張を伴って相変態するので、微細クラックが発生して強度・靭性が低下する、すなわち劣化することが指摘されている。この欠点を改善するために、出発原料であるジルコニア粉末の成形及び焼結性を様々な観点から改良して、ジルコニアセラミックスの耐劣化性を向上させてきている。 Since zirconia ceramics exhibit high strength and high toughness, they are used in a wide range of applications such as optical connector parts, precision processed parts, grinding media, pulverizer parts, blades and the like. However, when such zirconia ceramics having high strength and high toughness are exposed to a temperature of 200 to 300 ° C. for a long time in the air, the tetragonal crystal, which is a metastable phase, is converted to a monoclinic crystal having a stable phase by about 4%. It has been pointed out that microcracks are generated and the strength and toughness are lowered, that is, deteriorated, because the phase transformation occurs with a volume expansion of%. In order to improve this defect, the deterioration and resistance of zirconia ceramics have been improved by improving the molding and sintering properties of the zirconia powder as a starting material from various viewpoints.
例えば、特許文献１の様に、結晶性含水塩化ジルコニアを密閉容器中で加熱してジルコニアを結晶化させ、密封を解いて加熱脱水し、乾燥又は仮焼して、粒径約０．５μｍのジルコニア微粒子を得る方法や、特許文献２の様には、塩化ジルコニル等に塩酸と水を加えた粉砕混合物を密封水熱容器中で回転しながら１００〜２２０℃で水熱処理を行い、冷却後減圧乾燥した後熱処理して０．２〜０．７μｍの凝集粒子径を有するジルコニア微粒子を得る方法が提案されている。
For example, as in
これらのジルコニア微粒子は微細なため低温で焼結するが、粒径（凝集粒径）が０．２μｍ以上で粒度範囲が狭く、なおかつ０．２μｍ以下の微粒子を有しないものであったため、成形性、均一な焼結性、焼結割れの点でまだ十分とは言えなかった。 Since these zirconia fine particles are fine, they are sintered at a low temperature. However, the particle size (aggregated particle size) is 0.2 μm or more, the particle size range is narrow, and there are no fine particles of 0.2 μm or less. In terms of uniform sinterability and sintering cracks, it was still not sufficient.
最近、焼結性のよいジルコニア粉末が特許文献３により提案されている。このジルコニア粉末は、粒径分布が０．２〜０．５μｍ，１〜３μｍに２つのピークを有するものであり、この粉末に少量のアルミナを含有させ、成形し焼結させると１３５０℃の温度で高密度のジルコニア焼結体が得られることが開示されている。しかし、特許文献３の粉末は１μｍ以上の粒子を多く含むものであった。 Recently, a zirconia powder having good sinterability has been proposed in Patent Document 3. This zirconia powder has two peaks in the particle size distribution of 0.2 to 0.5 μm and 1 to 3 μm. When this powder contains a small amount of alumina, and is molded and sintered, the temperature is 1350 ° C. It is disclosed that a high-density zirconia sintered body can be obtained. However, the powder of Patent Document 3 contains many particles having a size of 1 μm or more.
最近では、種々の用途での高性能化の要求がさらに高まってきており、特に使用環境の厳しい条件でも劣化しない信頼性の高いジルコニアセラミックスが望まれ、更に低い温度で焼結するジルコニア粉末が求められている。 Recently, there has been an increasing demand for higher performance in various applications. In particular, a highly reliable zirconia ceramic that does not deteriorate even under severe conditions of use is desired, and a zirconia powder that can be sintered at a lower temperature is desired. It has been.
本発明では、上記のような従来方法における欠点を解消した、成形性がよく、かつ、低温焼結性にも優れ、これらに加えて焼結体にしたときの品質の信頼性にも優れたジルコニア微粉末の提供、ならびにそのジルコニア微粉末を簡易なプロセスにより製造することのできる方法の提供を目的とするものである。 In the present invention, the disadvantages in the conventional method as described above are eliminated, the moldability is good, and the low-temperature sinterability is excellent. In addition to these, the quality of the sintered body is also excellent in reliability. An object of the present invention is to provide a zirconia fine powder and a method capable of producing the zirconia fine powder by a simple process.
本発明者らは、ジルコニア粉末の粒径分布と成形及び焼結性との関係について詳細に検討し、本発明に到達した。 The present inventors have studied in detail the relationship between the particle size distribution of zirconia powder and the molding and sintering properties, and have reached the present invention.
即ち、本発明は、
１）安定化剤としてイットリア，カルシア，マグネシア及びセリアの１種以上を含むジルコニア微粉末であって、該ジルコニア微粉末の平均粒径が０．５μｍ未満であり、かつ、粒径分布の累積カーブにおいて１μｍでの粒子の占める割合が１００％であるジルコニア微粉末。
２）粒径分布の累積カーブにおいて０．２μｍでの粒子の占める割合が１０〜９０％である上記１）記載のジルコニア微粉末。
３）粒径分布のピークが０．３〜０．５μｍの範囲内にあって、かつ、ピークの幅が０．０５〜０．２μｍの範囲内にある上記１）及び上記２）記載のジルコニア微粉末。
４）イットリアを２〜４モル％含み、かつ、単斜晶相率が２０〜７０％である結晶構造を有する上記１）乃至３）記載のジルコニア微粉末。
５）ジルコニア微粉末が一種以上の添加物を含む上記１）乃至４）記載のジルコニア微粉末。
６）該添加物の陽イオンが、ジルコニウムイオンのイオン半径よりも小さいイオン半径を有する陽イオン及び／又は価数が４価以外の陽イオンである上記５）記載のジルコニア微粉末。
７）添加物の陽イオンが、アルミニウム，珪素及びゲルマニウムの群から選ばれる一種以上の陽イオンである上記５）及至６）記載のジルコニア微粉末。
８）上記１）乃至７）記載のジルコニア微粉末をスラリーにして噴霧造粒することにより得られ、平均粒径が３０〜８０μｍ、軽装嵩密度が１．００〜１．４０ｇ／ｃｍ３であるジルコニア顆粒。
９）ジルコニウム塩水溶液の加水分解で得られる水和ジルコニアゾルを、乾燥，仮焼，粉砕してジルコニア粉末を得る方法において、該加水分解の反応率が９８％以上の条件下で得られる水和ジルコニアゾルに、安定化剤の原料としてイットリウム，カルシウム，マグネシウム及びセリウムの化合物の１種以上を添加して乾燥し、９００〜１２００℃の範囲で仮焼してジルコニア粉末を得、次いで該ジルコニア粉末の平均粒径が０．５μｍ以下になるまで、直径３ｍｍ以下のジルコニアボールを用いて湿式粉砕することを特徴とする上記１）乃至７）記載のジルコニア微粉末の製造方法。
１０）該イットリウムの化合物を酸化物換算で２〜４モル％添加することを特徴とする上記９）記載のジルコニア微粉末の製造方法、
からなるものである。
That is, the present invention
1) A zirconia fine powder containing at least one of yttria, calcia, magnesia and ceria as a stabilizer, the zirconia fine powder having an average particle size of less than 0.5 μm, and a cumulative curve of particle size distribution Zirconia fine powder in which the proportion of particles at 1 μm is 100%.
2) The fine zirconia powder according to 1) above, wherein the proportion of particles at 0.2 μm in the cumulative curve of particle size distribution is 10 to 90%.
3) The zirconia according to 1) and 2) above, wherein the peak of the particle size distribution is in the range of 0.3 to 0.5 μm and the width of the peak is in the range of 0.05 to 0.2 μm. Fine powder.
4) The zirconia fine powder according to any one of 1) to 3) above, which has a crystal structure containing 2 to 4 mol% of yttria and having a monoclinic phase ratio of 20 to 70%.
5) The zirconia fine powder according to 1) to 4) above, wherein the zirconia fine powder contains one or more additives.
6) The zirconia fine powder according to 5) above, wherein the cation of the additive is a cation having an ionic radius smaller than that of zirconium ions and / or a cation having a valence other than tetravalent.
7) The zirconia fine powder according to 5) to 6) above, wherein the cation of the additive is at least one cation selected from the group of aluminum, silicon and germanium.
8) Obtained by slurrying the zirconia fine powder described in 1) to 7) above into a slurry and having an average particle diameter of 30 to 80 μm and a light bulk density of 1.00 to 1.40 g / cm 3 . Zirconia granules.
9) In a method of obtaining a zirconia powder by drying, calcining and pulverizing a hydrated zirconia sol obtained by hydrolysis of an aqueous solution of zirconium salt, hydration obtained under a condition where the reaction rate of hydrolysis is 98% or more. One or more compounds of yttrium, calcium, magnesium and cerium are added to the zirconia sol as a raw material for the stabilizer, dried, and calcined in the range of 900 to 1200 ° C. to obtain a zirconia powder, and then the zirconia powder The method for producing a fine zirconia powder according to any one of 1) to 7) above, wherein wet pulverization is performed using zirconia balls having a diameter of 3 mm or less until the average particle size of the zirconia becomes 0.5 μm or less.
10) The method for producing a fine zirconia powder according to 9) above, wherein the yttrium compound is added in an amount of 2 to 4 mol% in terms of oxide.
It consists of
以下、本発明をさらに詳細に説明する。
本明細書において、ジルコニア微粉末に係わる「平均粒径」とは、体積基準で表される粒径分布の累積カーブが中央値（メディアン径；累積カーブの５０％に対応する粒径）である粒子と同じ体積の球の直径をいい、レーザー回折法による粒径分布測定装置によって測定することができる。「ピークの幅（σ）」とは、体積基準で与えられる粒径分布ピークの広がりの程度を表す指標であり、以下の数式１で定義される値をいう。
Hereinafter, the present invention will be described in more detail.
In the present specification, the “average particle size” related to the fine zirconia powder is a median value (median diameter; particle size corresponding to 50% of the cumulative curve) of the cumulative particle size distribution expressed by volume. The diameter of a sphere having the same volume as the particle, which can be measured by a particle size distribution measuring apparatus using a laser diffraction method. The “peak width (σ)” is an index representing the extent of the particle size distribution peak given on a volume basis, and is a value defined by the following
ここで、ｉは粒径分割番号であり、ｄｉ及びＦｉは、ｉ番目の粒径（μｍ），頻度分布値（％）である。μは以下の数式２で定義される。 Here, i is a particle size division number, and d i and F i are the i-th particle size (μm) and the frequency distribution value (%). μ is defined by Equation 2 below.
「結晶子径（ＤＸ）」とは、粉末Ｘ線回折（ＸＲＤ）法で測定される回折線のブラッグ角（θ）と機械的広がり幅を補正した回折線の半値幅（β）をそれぞれ求めて、以下の数式３で与えられるシェーラー式により算出されたものの値をいう。 “Crystallite diameter (D X )” means the Bragg angle (θ) of the diffraction line measured by the powder X-ray diffraction (XRD) method and the half width (β) of the diffraction line corrected for the mechanical spread width, respectively. The value obtained by the Scherrer equation given by Equation 3 below is obtained.
ここで、κ及びλは、それぞれシェーラー定数（κ＝１），測定Ｘ線の波長である。ジルコニア微粉末の結晶子径は、強度の最も強い回折線により求める。「安定化剤濃度」とは、安定化剤／（ＺｒＯ２＋安定化剤）の比率をモル％として表した値をいう。「単斜晶相率」とは、ＸＲＤ測定により単斜晶相の（１１１）及び（１１−１）面，正方晶相の（１１１）面，立方晶の（１１１）面の回折強度をそれぞれ求めて、以下の数式４により算出されたものの値をいう。 Here, κ and λ are the Scherrer constant (κ = 1) and the wavelength of the measurement X-ray, respectively. The crystallite diameter of the fine zirconia powder is determined from the diffraction line having the strongest intensity. “Stabilizer concentration” refers to a value expressed as mole% of the ratio of stabilizer / (ZrO 2 + stabilizer). “Monoclinic phase ratio” means the diffraction intensities of the (111) and (11-1) planes of the monoclinic phase, the (111) plane of the tetragonal phase, and the (111) plane of the cubic crystal by XRD measurement. The value obtained by the following Equation 4 is obtained.
ここで、Ｉは各回折線のピーク強度，添字ｍ，ｔ及びｃは、それぞれ単斜晶相，正方晶相，立方晶相を表す。「イオン半径」とは、Ｓｈａｎｎｏｎによって報告（Ａｃｔａ．Ｃｒｙｓｔａｌｌｏｇｒ．，Ａ３２，７５１−６７（１９７６）．）されている値のことをいう。「添加物含有量」とは、添加物／（ＺｒＯ２＋安定化剤＋添加物）の比率を重量％として表した値をいう。ここで、添加物は酸化物に換算した値である。 Here, I represents the peak intensity of each diffraction line, and subscripts m, t, and c represent a monoclinic phase, a tetragonal phase, and a cubic phase, respectively. The “ion radius” refers to a value reported by Shannon (Acta. Crystallogr., A32, 751-67 (1976).). “Additive content” refers to a value expressed as a percentage by weight of the additive / (ZrO 2 + stabilizer + additive) ratio. Here, the additive is a value converted to an oxide.
水和ジルコニアゾルに係わる「反応率」とは、水和ジルコニアゾル含有液を限外濾過して、その濾液中に存在する未反応物のジルコニウム量を誘導結合プラズマ発光分光分析により求めて、水和ジルコニアゾルの生成量を算出し、原料仕込量に対する水和ジルコニアゾル量の比率として表したものの値をいう。「平均粒径」とは、粒度分布測定装置または電子顕微鏡等で測定されるものであり、例えば光子相関法で得られたものの値をいう。 The “reaction rate” related to the hydrated zirconia sol is obtained by ultrafiltration of a hydrated zirconia sol-containing liquid and determining the amount of zirconium in the unreacted substance present in the filtrate by inductively coupled plasma emission spectrometry. The amount of zirconia sol produced is calculated and the value expressed as the ratio of the amount of hydrated zirconia sol to the amount of raw material charged. The “average particle diameter” is measured with a particle size distribution measuring apparatus or an electron microscope, and refers to a value obtained by, for example, a photon correlation method.
本発明のジルコニア微粉末は、安定化剤としてイットリア，カルシア，マグネシア及びセリアの１種以上を含むことを必須とする。上記の安定化剤を含まないジルコニア微粉末を成形し焼結させると、焼結時にマルテンサイト変態に伴う膨張・収縮が起こり、その結果として材料が破壊するため、セラミックス原料粉末に適さないものとなるからである。また、上記のジルコニア微粉末は、平均粒径が０．５μｍ未満であり、かつ、粒径分布の累積カーブにおいて１μｍでの粒子の占める割合が１００％でなければならない。平均粒径が０．５μｍ以上、又は、粒径１μｍでの粒子の占める割合が１００％未満になると、硬い凝集粒子を含む粗粒が多くなるために、成形しにくいものとなり、かつ、粗粒が焼結の緻密化を阻害するために焼結性の悪いものとなるからである。好ましい平均粒径は０．０５〜０．４μｍであり、より好ましくは０．０５〜０．３μｍである。特に、粒径０．２μｍでの粒子の占める割合が１０〜９０％の範囲内にあれば、さらに成形しやすいものとなる。より好ましい割合は２０〜８０％であり、望ましくは３０〜７０％である。
上記の条件に付け加えて、１μｍ以下の範囲で、粒径分布のピークが０．３〜０．５μｍの範囲内にあって、かつ、ピークの幅が０．０５〜０．２μｍの範囲内にあれば、さらに焼結性のよいものとなる。
The zirconia fine powder of the present invention must contain at least one of yttria, calcia, magnesia and ceria as a stabilizer. When molding and sintering zirconia fine powder that does not contain the above stabilizers, expansion and contraction associated with martensite transformation occurs during sintering, and as a result, the material is destroyed. Because it becomes. The fine zirconia powder must have an average particle size of less than 0.5 μm, and the proportion of particles at 1 μm in the cumulative curve of particle size distribution must be 100%. When the average particle size is 0.5 μm or more, or the proportion of particles with a particle size of 1 μm is less than 100%, the number of coarse particles containing hard agglomerated particles increases. This is because, since the densification of sintering is inhibited, the sinterability becomes poor. A preferable average particle diameter is 0.05 to 0.4 μm, and more preferably 0.05 to 0.3 μm. In particular, if the proportion of particles having a particle size of 0.2 μm is in the range of 10 to 90%, molding becomes easier. A more desirable ratio is 20 to 80%, and desirably 30 to 70%.
In addition to the above conditions, in the range of 1 μm or less, the particle size distribution peak is in the range of 0.3 to 0.5 μm, and the peak width is in the range of 0.05 to 0.2 μm. If present, the sinterability is further improved.
また、上記のジルコニア微粉末は、ＢＥＴ比表面積が１１〜１９ｍ２／ｇ、結晶子径が２６〜５０ｎｍの範囲内にあれば、よりいっそう成形しやすいものとなる。より好ましいＢＥＴ比表面積は１２〜１９ｍ２／ｇであり、結晶子径は３０〜４０ｎｍである。 Moreover, if said BZ specific surface area is in the range of 11-19 m < 2 > / g and crystallite diameter is 26-50 nm, said zirconia fine powder will become still easier to shape | mold. A more preferable BET specific surface area is 12 to 19 m 2 / g, and a crystallite diameter is 30 to 40 nm.
ジルコニアセラミックスの特性は、安定化剤の種類や濃度によって変化するので、必要に応じて安定化剤を選択し、安定化剤の濃度を設定すればよい。安定化剤がジルコニア粒子に固溶しているものであれば、焼結の緻密化が均一に進行するのでより好ましいものとなる。特に、安定化剤としてイットリアを２〜４モル％含み、かつ、単斜晶相率が２０〜７０％である結晶構造を有するものであれば、成形し焼結させて得られる焼結体に残る気孔のサイズが小さくなり、かつ、その数が少なくなり、従って高密度の焼結体となって、機械的強度及び靭性に優れたジルコニアセラミックスとなる。より好ましいイットリア濃度は２．３〜３．５モル％であり、単斜晶相率は２０〜４０％である。 Since the characteristics of zirconia ceramics vary depending on the type and concentration of the stabilizer, the stabilizer may be selected as necessary and the concentration of the stabilizer may be set. If the stabilizer is a solid solution in the zirconia particles, the densification of sintering proceeds uniformly, which is more preferable. In particular, as long as it contains 2 to 4 mol% of yttria as a stabilizer and has a crystal structure with a monoclinic phase ratio of 20 to 70%, a sintered body obtained by molding and sintering is used. The size of the remaining pores is reduced and the number thereof is reduced, so that the sintered body becomes a high-density sintered body and becomes zirconia ceramics excellent in mechanical strength and toughness. A more preferable yttria concentration is 2.3 to 3.5 mol%, and a monoclinic phase rate is 20 to 40%.
さらに、上記のジルコニア微粉末が一種以上の添加物を含むと、成形して焼結する際の緻密化速度が促進されるので、よりいっそう焼結性に優れたものになる。このようなジルコニア微粉末を原料に用いて、成形し焼結させると、低い焼結温度で高密度の焼結体が得られるので、上記のとおり、劣化しにくいものとなって、極めて信頼性の高いジルコニアセラミックスとなる。特に、添加物の陽イオンが、ジルコニウムイオンのイオン半径（０．８６オングストローム）よりも小さいイオン半径（ｒ）を有するもの及び／又は価数（Ｚ）が４価以外のものであれば、焼結の緻密化速度が著しく促進されるのでより好ましいものとなる。最適な添加物含有量は、酸化物換算で０．０５〜１重量％である。添加物の陽イオンとしては、アルミニウム（ｒ＝０．６８オングストローム，Ｚ＝３），珪素（ｒ＝０．５４オングストローム，Ｚ＝４）及びゲルマニウム（ｒ＝０．６７オングストローム，Ｚ＝４）の群から選ばれる１種以上のものが効果的であり、これらの中でアルミニウムとゲルマニウムの組合せが最もよい。 Furthermore, when the above zirconia fine powder contains one or more additives, the densification rate at the time of molding and sintering is accelerated, so that the sinterability is further improved. When such a zirconia fine powder is used as a raw material and then molded and sintered, a high-density sintered body can be obtained at a low sintering temperature. High zirconia ceramics. In particular, if the cation of the additive has an ionic radius (r) smaller than the ionic radius of zirconium ion (0.86 angstrom) and / or the valence (Z) is other than tetravalent, This is more preferable because the densification speed of the knot is significantly accelerated. The optimum additive content is 0.05 to 1% by weight in terms of oxide. Additive cations include aluminum (r = 0.68 angstrom, Z = 3), silicon (r = 0.54 angstrom, Z = 4) and germanium (r = 0.67 angstrom, Z = 4). One or more selected from the group is effective, and among these, the combination of aluminum and germanium is the best.
本発明で得られるジルコニア微粉末をスラリーにして噴霧乾燥することによりジルコニア顆粒が得られ、その粒径は３０〜８０μｍ、軽装嵩密度が１．１０〜１．４０ｇ／ｃｍ３となる。 The zirconia fine powder obtained in the present invention is made into a slurry and spray-dried to obtain zirconia granules having a particle size of 30 to 80 μm and a light bulk density of 1.10 to 1.40 g / cm 3 .
顆粒の製造方法については、特に限定されないが、例えば、特開平１０−１９４７４３に記載の方法により、本発明で得られるジルコニア微粉末からジルコニア顆粒を製造することが可能である。 Although it does not specifically limit about the manufacturing method of a granule, For example, it is possible to manufacture a zirconia granule from the zirconia fine powder obtained by this invention by the method of Unexamined-Japanese-Patent No. 10-194743.
本発明のジルコニア微粉末を得るにあたっては、ジルコニウム塩水溶液の加水分解で得られる水和ジルコニアゾルを、乾燥，仮焼，粉砕してジルコニア粉末を得る方法において、該加水分解の反応率が９８％以上の条件下で得られる水和ジルコニアゾルに、安定化剤の原料としてイットリウム，カルシウム，マグネシウム及びセリウムの化合物の１種以上を添加して乾燥することを必要とする。水和ジルコニアゾルの生成率が９８％よりも小さくなると、仮焼時に未反応物に起因する粒子間の強固な焼結が起るために、粒子間の凝集性が著しく、かつ、硬い凝集粒子を含む粗粒も多くなって、上記のとおり、成形しにくく、かつ、焼結性の悪いものとなるからである。より好ましい反応率は９９％以上である。 In obtaining the zirconia fine powder of the present invention, in a method of obtaining a zirconia powder by drying, calcining and pulverizing a hydrated zirconia sol obtained by hydrolysis of an aqueous zirconium salt solution, the hydrolysis reaction rate is 98%. It is necessary to add one or more of yttrium, calcium, magnesium and cerium compounds as a stabilizer raw material to the hydrated zirconia sol obtained under the above conditions and dry it. When the rate of formation of the hydrated zirconia sol is less than 98%, strong sintering occurs between the particles due to unreacted substances during calcination. This is because the number of coarse particles including, increases, and as described above, is difficult to mold and has poor sinterability. A more preferable reaction rate is 99% or more.
水和ジルコニアゾルと安定化剤の原料化合物との混合方法に制限はなく、例えば加水分解後の水和ジルコニアゾル含有液に安定化剤の原料化合物を所定量添加してもよく、あるいは加水分解前のジルコニウム塩水溶液に前もって添加していてもよい。安定化剤の原料に用いられる化合物としては、塩化物，フッ化物，硝酸塩，炭酸塩，硫酸塩，酢酸塩，酸化物，水酸化物などを挙げることができる。安定化剤の原料としてイットリウム化合物を酸化物換算で２〜４モル％添加すると、上記の仮焼及び粉砕条件で得られるジルコニア微粉末の単斜晶相率が２０〜７０％の範囲内となり、前記のとおり、機械的強度及び靭性に優れたものになる。より好ましいイットリア濃度は２．３〜３．５モル％である。また、水和ジルコニアゾルの乾燥方法については、例えば、混合溶液をそのまま、または該混合溶液に有機溶媒を添加して噴霧乾燥する方法、該混合溶液にアルカリなどを添加して濾過，水洗したあとに乾燥する方法を挙げることができる。 There is no restriction on the method of mixing the hydrated zirconia sol and the raw material of the stabilizer. For example, a predetermined amount of the raw material of the stabilizer may be added to the hydrous hydrated zirconia sol-containing liquid, or hydrolysis may be performed. It may be added in advance to the previous aqueous zirconium salt solution. Examples of the compound used as the raw material for the stabilizer include chloride, fluoride, nitrate, carbonate, sulfate, acetate, oxide, hydroxide and the like. When 2-4 mol% of yttrium compound is added in terms of oxide as a raw material for the stabilizer, the monoclinic phase ratio of the zirconia fine powder obtained under the above calcining and pulverization conditions is in the range of 20-70%, As described above, the mechanical strength and toughness are excellent. A more preferred yttria concentration is 2.3 to 3.5 mol%. As for the method of drying the hydrated zirconia sol, for example, the mixed solution is used as it is or spray-dried by adding an organic solvent to the mixed solution, and after adding alkali or the like to the mixed solution and filtering and washing with water. The method of drying can be mentioned.
上記の水和ジルコニアゾルは、ジルコニウム塩水溶液の加水分解で、反応率が９８％以上を満足しているものが得られる方法であれば、いかなる反応条件で得られたものでもよい。例えば、ジルコニウム塩水溶液を調製して加水分解させる、ジルコニウム塩水溶液にアルカリまたは酸などを所定量添加して加水分解させる、陰イオン交換樹脂によりジルコニウム塩を構成している陰イオンの一部を除去して加水分解させる、水酸化ジルコニウムと酸との混合スラリーを加水分解させる、加水分解で得られた水和ジルコニアゾルをジルコニウム塩水溶液に所定量添加して加水分解させる、などの方法を挙げることができる。 The hydrated zirconia sol may be obtained under any reaction conditions as long as the reaction rate is 98% or more by hydrolysis of the aqueous zirconium salt solution. For example, an aqueous solution of zirconium salt is prepared and hydrolyzed, a predetermined amount of alkali or acid is added to the aqueous solution of zirconium salt and hydrolyzed, and a part of the anion constituting the zirconium salt is removed by an anion exchange resin. To hydrolyze, to hydrolyze a mixed slurry of zirconium hydroxide and acid, to add a predetermined amount of hydrated zirconia sol obtained by hydrolysis to an aqueous solution of zirconium salt and to hydrolyze Can do.
とくに、ジルコニウム塩水溶液の加水分解で得られた水和ジルコニアゾル含有液の一部を反応槽から連続及び／又は間欠的に排出し、かつ、当該水和ジルコニアゾル含有液の体積が一定に保たれるように、その排出量と同量のジルコニウム塩水溶液を連続及び／又は間欠的に反応槽に供給しながら加水分解させると、より反応率の高い水和ジルコニアゾルが効率よく得られるので効果的である。上記の方法で得られた水和ジルコニアゾルを限外濾過膜で水洗処理すると、未反応物をほとんど含まなくなるので、さらに焼結性に優れたものになる。 In particular, a part of the hydrated zirconia sol-containing liquid obtained by hydrolysis of the zirconium salt aqueous solution is continuously and / or intermittently discharged from the reaction tank, and the volume of the hydrated zirconia sol-containing liquid is kept constant. As a result, hydrolyzing while supplying an aqueous zirconium salt solution of the same amount as the discharge amount to the reaction vessel continuously and / or intermittently is effective because a hydrated zirconia sol with a higher reaction rate can be obtained efficiently. Is. When the hydrated zirconia sol obtained by the above-described method is washed with an ultrafiltration membrane, it contains almost no unreacted substance, so that the sinterability is further improved.
上記の条件に付け加えて、水和ジルコニアゾルの平均粒径が、０．０５〜０．２μｍの範囲にあれば、さらに成形しやすいものとなる。水和ジルコニアゾルの平均粒径を制御する場合には、反応終了時の反応液のｐＨを調整して制御することにより所望の平均粒径をもつ水和ジルコニアゾルを得ることができる。例えば、反応終了時のｐＨが０．３〜０．６または０．８〜１．４となるように調整すると、平均粒径０．０５〜０．２μｍの水和ジルコニアゾルが得られる。このｐＨすなわち水和ジルコニアゾルの平均粒径を制御する方法としては、ジルコニウム塩水溶液にアルカリまたは酸を添加する、陰イオン交換樹脂によりジルコニウム塩を構成している陰イオンの一部を除去することによりｐＨを調整して加水分解させる、水酸化ジルコニウムと酸との混合スラリーのｐＨを調整して加水分解させるなどの方法を挙げることができる。 In addition to the above conditions, if the average particle size of the hydrated zirconia sol is in the range of 0.05 to 0.2 μm, it becomes easier to mold. When controlling the average particle size of the hydrated zirconia sol, a hydrated zirconia sol having a desired average particle size can be obtained by adjusting and controlling the pH of the reaction solution at the end of the reaction. For example, when the pH at the end of the reaction is adjusted to 0.3 to 0.6 or 0.8 to 1.4, a hydrated zirconia sol having an average particle size of 0.05 to 0.2 μm is obtained. As a method for controlling the pH, that is, the average particle diameter of the hydrated zirconia sol, an alkali or acid is added to the zirconium salt aqueous solution, and a part of the anions constituting the zirconium salt is removed by an anion exchange resin. Examples thereof include a method of adjusting the pH by hydrolyzing and hydrolyzing by adjusting the pH of the mixed slurry of zirconium hydroxide and acid.
水和ジルコニアゾルの製造に用いられるジルコニウム塩としては、オキシ塩化ジルコニウム，硝酸ジルコニル，塩化ジルコニウム，硫酸ジルコニウムなどが挙げられるが、この他に水酸化ジルコニウムと酸との混合物を用いてもよい。水和ジルコニアゾルの平均粒径を制御するために添加するアルカリとしては、アンモニア，水酸化ナトリウム，水酸化カリウムなどを挙げることができるが、これらの他に尿素のように分解して塩基性を示す化合物でもよい。また、酸としては塩酸，硝酸，硫酸を挙げることができるが、これらの他に酢酸，クエン酸などの有機酸を用いてもよい。 Zirconium salts used for the production of the hydrated zirconia sol include zirconium oxychloride, zirconyl nitrate, zirconium chloride, zirconium sulfate and the like, but in addition, a mixture of zirconium hydroxide and acid may be used. Examples of the alkali added to control the average particle diameter of the hydrated zirconia sol include ammonia, sodium hydroxide, potassium hydroxide, and the like. The compound shown may be sufficient. Examples of the acid include hydrochloric acid, nitric acid, and sulfuric acid, but in addition to these, organic acids such as acetic acid and citric acid may be used.
次いで、本発明では、上記で得られた水和ジルコニアゾルの乾燥粉を９００〜１２００℃の温度で仮焼しなければならない。仮焼温度がこの範囲外になると、本発明の下記粉砕条件で得られるジルコニア微粉末の凝集性が著しく強くなって、あるいは硬い凝集粒子を含む粗粒が多くなるために平均粒径が０．５μｍ以上、かつ、粒径分布の累積カーブにおける１μｍでの粒子の占める割合が１００％未満となって、本発明のジルコニア微粉末が得られなくなるからである。より好ましい仮焼温度は９００〜１１００℃である。仮焼温度の保持時間は０．５〜１０時間がよく、昇温速度は０．５〜１０℃／ｍｉｎが好ましい。保持時間が０．５よりも短くなると均一に仮焼されにくく、１０時間よりも長くなると生産性が低下するので好ましくない。また、昇温速度が０．５℃／ｍｉｎよりも小さくなると設定温度に達するまでの時間が長くなり、１０℃／ｍｉｎよりも大きくなると仮焼時に粉末が激しく飛散して操作性が悪くなり生産性が低下する。 Next, in the present invention, the dried powder of the hydrated zirconia sol obtained above must be calcined at a temperature of 900 to 1200 ° C. If the calcining temperature is outside this range, the agglomeration property of the zirconia fine powder obtained under the following pulverization conditions of the present invention becomes remarkably strong, or the average particle size becomes 0.00 because the number of coarse particles containing hard agglomerated particles increases. This is because the proportion of particles at 5 μm or more and the particle size distribution cumulative curve of 1 μm is less than 100%, and the zirconia fine powder of the present invention cannot be obtained. A more preferable calcining temperature is 900 to 1100 ° C. The holding time of the calcining temperature is preferably 0.5 to 10 hours, and the temperature raising rate is preferably 0.5 to 10 ° C./min. If the holding time is shorter than 0.5, uniform calcination is difficult, and if it is longer than 10 hours, the productivity is lowered, which is not preferable. Also, if the rate of temperature rise is less than 0.5 ° C / min, the time until the set temperature is reached is longer, and if it is greater than 10 ° C / min, the powder scatters vigorously during calcination, resulting in poor operability and production. Sex is reduced.
次いで、上記で得られた仮焼粉を平均粒径が０．５μｍ以下になるまで、直径３ｍｍ以下のジルコニアボールを用いて湿式粉砕することを必要とする。直径が３ｍｍよりも大きいジルコニアボールを用いて湿式粉砕すると、平均粒径が０．５μｍよりも大きく、かつ、粒径分布の累積カーブにおける粒径０．２μｍ、１μｍにおいて粒子の占める割合がそれぞれ５％未満、９０％未満のものとなって、本発明のジルコニア微粉末が得られなくなるからである。より好ましいジルコニアボールの直径は２ｍｍ以下である。粉砕機器としては、振動ミル，連続式媒体撹拌ミルを用いればよい。また、粉砕条件は、機種により異なるが、振動ミルの場合、スラリー濃度３０〜６０ｗｔ％，２０〜３０時間がよく、媒体撹拌ミルの場合、スラリー濃度３０〜６０ｗｔ％，１５〜３０時間が最適である。粉砕する前に、仮焼粉を水洗処理、あるいは稀薄なアンモニア水で洗浄処理すると、ジルコニウム塩原料に由来する、焼結を阻害する微量の不純物が除去されるので、焼結性を向上させるのに効果的である。 Next, it is necessary to wet pulverize the calcined powder obtained above using zirconia balls having a diameter of 3 mm or less until the average particle diameter becomes 0.5 μm or less. When wet pulverization is performed using zirconia balls having a diameter larger than 3 mm, the average particle size is larger than 0.5 μm, and the proportion of particles in the cumulative curve of the particle size distribution is 5 μm and 1 μm, respectively. This is because the zirconia fine powder of the present invention cannot be obtained. A more preferable diameter of the zirconia ball is 2 mm or less. As a grinding device, a vibration mill or a continuous medium stirring mill may be used. The grinding conditions vary depending on the model, but in the case of a vibration mill, a slurry concentration of 30 to 60 wt% and 20 to 30 hours is good, and in the case of a medium stirring mill, the slurry concentration of 30 to 60 wt% and 15 to 30 hours is optimal. is there. Washing the calcined powder with water or dilute ammonia water before pulverization removes a small amount of impurities that hinder sintering, which is derived from the zirconium salt raw material, thus improving the sinterability. It is effective.
必要に応じて、添加物を含むジルコニア微粉末を得る場合には、水和ジルコニアゾルに添加物を加えればよく、あるいは仮焼粉に添加物を加えて湿式粉砕すればよい。添加物の陽イオンがアルミニウムである原料化合物としては、アルミナ，水和アルミナ，アルミナゾル，水酸化アルミニウム，塩化アルミニウム，硝酸アルミニウム，硫酸アルミニウムなどを挙げることができる。陽イオンが珪素である原料化合物としては、シリカ、シリカゾル、ケイ酸などが挙げられる。また、陽イオンがゲルマニウムである原料化合物としては、酸化ゲルマニウム，水酸化ゲルマニウムなどを挙げることができる。 If necessary, when obtaining a zirconia fine powder containing an additive, the additive may be added to the hydrated zirconia sol, or the additive may be added to the calcined powder and wet pulverized. Examples of the raw material compound in which the cation of the additive is aluminum include alumina, hydrated alumina, alumina sol, aluminum hydroxide, aluminum chloride, aluminum nitrate, and aluminum sulfate. Examples of the raw material compound whose cation is silicon include silica, silica sol, and silicic acid. Examples of the raw material compound whose cation is germanium include germanium oxide and germanium hydroxide.
以上、説明したとおり、本発明のジルコニア微粉末は、成形性及び低温焼結性がよく、さらに焼結体にしたときの品質の信頼性にも優れている。また、本発明の方法により、容易に上記のジルコニア微粉末を製造することができる。 As described above, the zirconia fine powder of the present invention has good moldability and low-temperature sinterability, and also has excellent quality reliability when formed into a sintered body. In addition, the above zirconia fine powder can be easily produced by the method of the present invention.
以下、実施例により本発明を具体的に説明するが、本発明はこれらの実施例に何等限定されるものではない。 EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples at all.
例中、水和ジルコニアゾルの平均粒径は、光子相関法による粒度分布測定装置により求めた。ジルコニア微粉末の平均粒径は、マイクロトラック粒度分布計（Ｈｏｎｅｙｗｅｌｌ社製，９３２０−ＨＲＡ）を用いて測定した。試料の前処理条件としては、粉末を蒸留水に懸濁させ、超音波ホモジナイザー（日本精機製作所製，ＵＳ−１５０Ｔ）を用いて３分間分散させた。粒径分布のピークの幅は、粒径０．２〜１μｍの範囲で測定された粒径と頻度分布値を、数式１及び２に代入して求めた。結晶子径は、ＸＲＤ測定により得られる正方晶の（１１１）面の回折線を用いて数式３より求め、単斜晶相率は数式４より算出した（いずれの例においても、立方晶は含まれていなかった）。
又、ジルコニア顆粒の平均粒径は、ふるい分け試験方法によって求めた。
In the examples, the average particle size of the hydrated zirconia sol was determined by a particle size distribution measuring apparatus using a photon correlation method. The average particle size of the zirconia fine powder was measured using a Microtrac particle size distribution meter (manufactured by Honeywell, 9320-HRA). As sample pretreatment conditions, the powder was suspended in distilled water and dispersed using an ultrasonic homogenizer (Nippon Seiki Seisakusho, US-150T) for 3 minutes. The width of the peak of the particle size distribution was obtained by substituting the particle size and frequency distribution value measured in the range of 0.2 to 1 μm into
Moreover, the average particle diameter of the zirconia granule was determined by a screening test method.
原料粉末の成形は、金型プレスにより成形圧力７００ｋｇｆ／ｃｍ２で行い、得られた成形体は所定温度（保持時間２ｈ）に設定して焼結させた。得られた焼結体の相対密度は、アルキメデス法で測定し、理論密度を６．０８ｇ／ｃｍ３として算出した。焼結体の強度は、３点曲げ測定法で評価した。また、劣化試験は、焼結体を１４０℃の熱水中に７２時間浸漬させ、生成する単斜晶相の比率（単斜晶相率）を求めることによって評価した。単斜晶相率は、浸漬処理した焼結体についてＸＲＤ測定を行い、ジルコニア微粉末の単斜晶相率と同様の算出方法で、数式４により求めた。 The raw material powder was molded by a mold press at a molding pressure of 700 kgf / cm 2 , and the obtained molded body was sintered at a predetermined temperature (holding time 2 h). The relative density of the obtained sintered body was measured by Archimedes method, and the theoretical density was calculated as 6.08 g / cm 3 . The strength of the sintered body was evaluated by a three-point bending measurement method. In addition, the deterioration test was evaluated by immersing the sintered body in hot water at 140 ° C. for 72 hours and determining the ratio of the monoclinic phase to be formed (monoclinic phase ratio). The monoclinic phase rate was obtained by Equation 4 using the same calculation method as that of the monoclinic phase rate of the zirconia fine powder by performing XRD measurement on the sintered body subjected to the immersion treatment.
実施例１
２モル／リットルのオキシ塩化ジルコニウム水溶液４リットルに２モル／リットルのアンモニア水４．８リットルを混合し、蒸留水を加えてジルコニア換算濃度０．８モル／リットルの溶液を調製した。この溶液を還流器付きフラスコ中で攪拌しながら加水分解反応を煮沸温度で２００時間行った。得られた水和ジルコニアゾルの反応率は９８％であり、平均粒径は０．１μｍであった。この水和ジルコニアゾルに塩化イットリウムをイットリア濃度が３モル％になるように添加して乾燥させ、１０００℃の温度で２時間仮焼した。
Example 1
4.8 liters of 2 mol / liter ammonia water was mixed with 4 liters of 2 mol / liter zirconium oxychloride aqueous solution, and distilled water was added to prepare a solution having a zirconia equivalent concentration of 0.8 mol / liter. While stirring this solution in a flask equipped with a reflux condenser, the hydrolysis reaction was carried out at the boiling temperature for 200 hours. The reaction rate of the obtained hydrated zirconia sol was 98%, and the average particle size was 0.1 μm. To this hydrated zirconia sol, yttrium chloride was added to a yttria concentration of 3 mol%, dried, and calcined at a temperature of 1000 ° C. for 2 hours.
得られた仮焼粉を水洗処理したあとに、アルミナゾルをアルミナ含有量が０．２５重量％になるように添加し、さらに蒸留水を加えてジルコニア濃度４５重量％のスラリーにした。このスラリーを直径２ｍｍのジルコニアボールを用いて、振動ミルで２４時間粉砕して乾燥させた。得られたジルコニア微粉末の平均粒径，粒径０．２μｍ及び１μｍでの粒子の占める割合，０．４μｍ付近に存在するピークの幅，結晶子径，単斜晶相率の値を表１に示す。 After the obtained calcined powder was washed with water, alumina sol was added so that the alumina content was 0.25% by weight, and distilled water was further added to make a slurry having a zirconia concentration of 45% by weight. This slurry was pulverized for 24 hours with a vibration mill using zirconia balls having a diameter of 2 mm and dried. Table 1 shows the average particle size of the obtained fine zirconia powder, the proportion of particles at particle sizes of 0.2 μm and 1 μm, the width of the peak existing around 0.4 μm, the crystallite diameter, and the monoclinic phase ratio. Shown in
次いで、上記で得られたジルコニア微粉末をプレス成形し１２５０℃の条件で焼結させた。得られた焼結体の相対密度，曲げ強度，劣化試験後の単斜晶相率を表２に示す。劣化試験後の単斜晶相率が０％であることから、極めて劣化しにくい信頼性の高い焼結体であることが確認された。 Subsequently, the zirconia fine powder obtained above was press-molded and sintered under the condition of 1250 ° C. Table 2 shows the relative density, bending strength, and monoclinic phase rate after the deterioration test of the obtained sintered body. Since the monoclinic phase ratio after the deterioration test was 0%, it was confirmed that the sintered body was highly reliable and hardly deteriorated.
実施例２
実施例１の水和ジルコニアゾルに蒸留水を加えて、ジルコニア換算濃度０．３モル／リットルの溶液を調製した。これを出発溶液に用いて、溶液の５体積％を反応槽から間欠的に排出し、かつ、溶液の体積が一定に保たれるように、その排出量と同量の０．３モル／リットルのオキシ塩化ジルコニウム水溶液を３０分毎に反応槽に供給しながら煮沸温度で加水分解反応を２００時間行った。反応槽から排出された水和ジルコニアゾルの反応率は９９％であり、平均粒径は０．１μｍであった。この水和ジルコニアゾルを限外濾過膜で水洗処理したあとに、塩化イットリウムをイットリア濃度が３モル％になるように添加して乾燥させ、９９０℃の温度で２時間仮焼した。得られた仮焼粉を水洗処理したあとに、蒸留水を加えてジルコニア濃度４５重量％のスラリーにした。このスラリーを直径２ｍｍのジルコニアボールを用いて、振動ミルで２４時間粉砕して乾燥させた。得られたジルコニア微粉末の特性を表１に示す。また、ジルコニア微粉末の粒径分布（頻度及び累積カーブ）を図１に示す。
Example 2
Distilled water was added to the hydrated zirconia sol of Example 1 to prepare a solution having a zirconia equivalent concentration of 0.3 mol / liter. Using this as a starting solution, 5% by volume of the solution is intermittently discharged from the reaction vessel, and 0.3 mol / liter of the same amount as the discharged amount so that the volume of the solution is kept constant. The hydrolysis reaction was carried out for 200 hours at the boiling temperature while supplying the zirconium oxychloride aqueous solution to the reaction vessel every 30 minutes. The reaction rate of the hydrated zirconia sol discharged from the reaction vessel was 99%, and the average particle size was 0.1 μm. After this hydrated zirconia sol was washed with an ultrafiltration membrane, yttrium chloride was added to a yttria concentration of 3 mol%, dried, and calcined at a temperature of 990 ° C. for 2 hours. The obtained calcined powder was washed with water, and distilled water was added to make a slurry having a zirconia concentration of 45% by weight. This slurry was pulverized for 24 hours with a vibration mill using zirconia balls having a diameter of 2 mm and dried. The characteristics of the obtained zirconia fine powder are shown in Table 1. The particle size distribution (frequency and cumulative curve) of the zirconia fine powder is shown in FIG.
次いで、上記で得られたジルコニア微粉末をプレス成形し１３５０℃の条件で焼結させた。得られた焼結体の特性を表２に示す。劣化試験後の単斜晶相率が２％であることから、劣化しにくい焼結体であることが確認された。 Subsequently, the zirconia fine powder obtained above was press-molded and sintered under the condition of 1350 ° C. Table 2 shows the characteristics of the obtained sintered body. Since the monoclinic phase ratio after the deterioration test was 2%, it was confirmed that the sintered body was not easily deteriorated.
実施例３
仮焼粉を水洗処理したあとに、アルミナゾルをアルミナ含有量が０．２５重量％になるように添加した以外は、実施例２と同様の条件でジルコニア微粉末を得た。ジルコニア微粉末の特性を表１に示す。
Example 3
A zirconia fine powder was obtained under the same conditions as in Example 2 except that after the calcined powder was washed with water, alumina sol was added so that the alumina content was 0.25 wt%. The characteristics of the zirconia fine powder are shown in Table 1.
次いで、上記で得られたジルコニア微粉末をプレス成形し１２５０℃の条件で焼結させた。得られた焼結体の特性を表２に示す。劣化試験後の単斜晶相率が０％であることから、極めて劣化しにくい信頼性の高い焼結体であることが確認された。 Subsequently, the zirconia fine powder obtained above was press-molded and sintered under the condition of 1250 ° C. Table 2 shows the characteristics of the obtained sintered body. Since the monoclinic phase ratio after the deterioration test was 0%, it was confirmed that the sintered body was highly reliable and hardly deteriorated.
実施例４
アルミナゾルの代りに、酸化ゲルマニウムを０．２５重量％添加した以外は、実施例２と同様の条件でジルコニア微粉末を得た。ジルコニア微粉末の特性を表１に示す。
Example 4
Zirconia fine powder was obtained under the same conditions as in Example 2 except that 0.25% by weight of germanium oxide was added instead of alumina sol. The characteristics of the zirconia fine powder are shown in Table 1.
次いで、上記で得られたジルコニア微粉末をプレス成形し１３００℃の条件で焼結させた。得られた焼結体の特性を表２に示す。劣化試験後の単斜晶相率が１％であることから、劣化しにくい焼結体であることが確認された。 Subsequently, the zirconia fine powder obtained above was press-molded and sintered at 1300 ° C. Table 2 shows the characteristics of the obtained sintered body. Since the monoclinic phase ratio after the deterioration test was 1%, it was confirmed that the sintered body was not easily deteriorated.
実施例５
アルミナゾルの代りに、アルミナゾルをアルミナ含有量０．２５重量％及び酸化ゲルマニウムを０．２５重量％添加した以外は、実施例１と同様の条件でジルコニア微粉末を得た。ジルコニア微粉末の特性を表１に示す。
Example 5
A zirconia fine powder was obtained under the same conditions as in Example 1 except that alumina content was 0.25 wt% and germanium oxide was added 0.25 wt% instead of alumina sol. The characteristics of the zirconia fine powder are shown in Table 1.
次いで、上記で得られたジルコニア微粉末をプレス成形し１２００℃の条件で焼結させた。得られた焼結体の特性を表２に示す。劣化試験後の単斜晶相率が０％であることから、極めて劣化しにくい信頼性の高い焼結体であることが確認された。 Subsequently, the zirconia fine powder obtained above was press-molded and sintered at 1200 ° C. Table 2 shows the characteristics of the obtained sintered body. Since the monoclinic phase ratio after the deterioration test was 0%, it was confirmed that the sintered body was highly reliable and hardly deteriorated.
実施例６
実施例３で得られたジルコニア微粉末を水に分散させてスラリー濃度５０％のジルコニアスラリーを得、このスラリーに増粘剤を添加して粘度調整を行ったあとに噴霧造粒を実施した。得られたジルコニア顆粒の平均粒径が５５μｍ、軽装嵩密度が１．２９ｇ／ｃｍ３であった。
Example 6
The zirconia fine powder obtained in Example 3 was dispersed in water to obtain a zirconia slurry having a slurry concentration of 50%. After the viscosity was adjusted by adding a thickener to this slurry, spray granulation was performed. The obtained zirconia granules had an average particle size of 55 μm and a light bulk density of 1.29 g / cm 3 .
次いで、上記で得られたジルコニア微粉末をプレス成形し１２５０℃の条件で焼結させた。得られた焼結体の特性を表２に示す。劣化試験後の単斜晶相率が０％であることから、極めて劣化しにくい信頼性の高い焼結体であることが確認された。 Subsequently, the zirconia fine powder obtained above was press-molded and sintered under the condition of 1250 ° C. Table 2 shows the characteristics of the obtained sintered body. Since the monoclinic phase ratio after the deterioration test was 0%, it was confirmed that the sintered body was highly reliable and hardly deteriorated.
比較例１
０．３８モル／リットルのオキシ塩化ジルコニウム水溶液を調製して、還流器付きフラスコ中で加水分解反応を煮沸温度で１９０時間行った。得られた水和ジルコニアゾルの反応率は８８％であり、平均粒径は０．１μｍであった。この水和ジルコニアゾル含有液に塩化イットリウムをイットリア濃度が３モル％になるように添加して乾燥させ、１０３０℃の温度で２時間仮焼した。得られた仮焼粉を水洗処理したあとに、蒸留水を加えてジルコニア濃度４５重量％のスラリーにした。このスラリーを直径１０ｍｍのジルコニアボールを用いて、振動ミルで３０時間粉砕して乾燥させた。得られたジルコニア微粉末の特性を表１に、粒径分布（頻度及び累積カーブ）を図２にそれぞれ示す。
Comparative Example 1
A 0.38 mol / liter aqueous solution of zirconium oxychloride was prepared, and the hydrolysis reaction was carried out at a boiling temperature for 190 hours in a flask equipped with a reflux condenser. The reaction rate of the obtained hydrated zirconia sol was 88%, and the average particle size was 0.1 μm. To this hydrated zirconia sol-containing solution, yttrium chloride was added to a yttria concentration of 3 mol%, dried, and calcined at a temperature of 1030 ° C. for 2 hours. The obtained calcined powder was washed with water, and distilled water was added to make a slurry having a zirconia concentration of 45% by weight. The slurry was pulverized with a vibration mill for 30 hours using zirconia balls having a diameter of 10 mm and dried. The characteristics of the obtained zirconia fine powder are shown in Table 1, and the particle size distribution (frequency and cumulative curve) is shown in FIG.
次いで、上記で得られたジルコニア微粉末をプレス成形し１３５０，１４００℃の条件でそれぞれ焼結させたが、得られた焼結体の相対密度が９６．７及び９８．５％と低いため、更に高い温度である１４５０℃で焼結させて得られた焼結体の特性を評価した。結果を表２に示す。劣化試験後の単斜晶相率が８６％であり、極めて劣化しやすい焼結体であることが確認された。 Next, the zirconia fine powder obtained above was press-molded and sintered under the conditions of 1350 ° C. and 1400 ° C., respectively, but the relative density of the obtained sintered body was as low as 96.7 and 98.5%. Further, the characteristics of the sintered body obtained by sintering at 1450 ° C., which is a higher temperature, were evaluated. The results are shown in Table 2. The monoclinic phase ratio after the deterioration test was 86%, and it was confirmed that the sintered body was extremely susceptible to deterioration.
比較例２
仮焼粉を水洗処理したあとに、アルミナ粉末をアルミナ含有量が０．２５重量％になるように添加した以外は、比較例１と同様の条件でジルコニア微粉末を得た。ジルコニア微粉末の特性を表１に示す。
Comparative Example 2
A zirconia fine powder was obtained under the same conditions as in Comparative Example 1 except that the calcined powder was washed with water and then the alumina powder was added so that the alumina content was 0.25 wt%. The characteristics of the zirconia fine powder are shown in Table 1.
次いで、上記で得られたジルコニア微粉末をプレス成形し１２５０，１３００℃の条件でそれぞれ焼結させたが、得られた焼結体の相対密度が９６．３及び９７．８％と低いため、更に高い温度である１３５０℃で焼結させて得られた焼結体の特性を評価した。結果を表２に示す。劣化試験後の単斜晶相率が１９％であり、劣化しやすい焼結体であることが確認された。 Next, the zirconia fine powder obtained above was press-molded and sintered under the conditions of 1250 and 1300 ° C., respectively, but the relative density of the obtained sintered body was as low as 96.3 and 97.8%. The characteristics of the sintered body obtained by sintering at a higher temperature of 1350 ° C. were evaluated. The results are shown in Table 2. The monoclinic phase ratio after the deterioration test was 19%, and it was confirmed that the sintered body was easily deteriorated.
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