ジルコニアの低温熱劣化に及ぼす原料粉末比表面積の影響

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Tetragonal zirconia polycrystals stabilized by Y_2O_3(Y-TZP) are recognized as a high strength material.However, Y-TZP has a fatal degradation at relatively low temperatures (100〜300℃) according to the trasformation from teragonal to manoclinic phase. This transformation was reported to depend on the grain in the sintered body. The purpose of the present study was to clarify the relationship between the properties of the starting powder and the low-temperature degradation of sintered specimens. The process and the results the results are as follows.(1) The fine raw powders of zirconia with specific surface area of 10, 20 and 30 m^2/g were prepared by hydrolysis of ZrOC1_2・8H_2O and Zr(OH)_4, coprecipitation of hydrated ZrO_2 and Y(OH)_3 by NH_4OH, and calcination in the temperature range of 800~1100℃. (2) These raw powders having specific surface area of 20 and 30 m^2/g could be sintered easily at 1300℃ and yielded the sintered bodies with small grain sizes. In these samples, the degradation could be scarcely observed even under a 200℃ hydrothermal condition. (3) The degradation in bending strength of Y-TZP by aging in hot water of 200℃ showed good correspondence with the increase of monoclinic phase by the aging. (4) When Y_2O_3 content and bulk density were ~xed, the degradation behavior was closely related to the grain size of the sintered body. The critical grain size of the phase transformation from tetragonal to monoclinic was about 0.3-0.4 14μm.
社団法人日本材料学会の論文
1990-06-15

ジルコニアの低温熱劣化に及ぼす原料粉末比表面積の影響

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