プレスフリー反応焼結による高密度熱収縮性酸化物セラミックスZr_<1-x>Y_xW_2O_<8-δ>(x=0.00〜0.02)の作製

概要

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By performing reactive sintering of a powder mixture of ZrO_2, Y_2O_3 and WO_3 (whose particle size distribution was 10-50 μ and of submicron-order), large pieces of dense Zr_<1-x>Y_xW_2O_<8-δ> oxide with a negative thermal expansion coefficient were prepared. The density of the sintered specimens prepared by such a press-free process was comparable with that of similar materials prepared by processes that include molding/pressing. It was found that the partial substitution of Y^<3+> for Zr^<4+> was effective for promoting grain growth, resulting in an increase of density. Zr_<0.98>Y_<0.02>W_2O_<8-δ> sintered bodies with density of 〜96% of a truncated cone shapewith upper diameter, lower diameter and height of 〜40 mm, 〜45 mm and 20-25 mm, respectively, were obtained. Negative thermal expansion was observed in all Zr_<1-x>Y_xW_2O_<8-δ> specimens (x=0.00-0.02), this coefficient being hardly affected by the Y^<3+> content. It was also found that only porous and fragile specimens could be prepared by using a mixture with particle size distribution of submicron order as the raw material. This was ascribed to the formation of second-order particles that tended not to sinter within larger particles.
社団法人日本セラミックス協会の論文
2002-09-01