化学的手法によるEu_2O_3-ZrO_2正方晶固溶体の合成, 焼結と相転移

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Dense zirconia-europia tetragonal solid solutions were obtained by sintering nanometer-sized powders produced by coprecipitation from solutions of zirconyl and europium nitrates hydrates. The tetragonal phase could be retained at room temperature for compositions of 2.0-4.0 mol% Eu_2O_3. The fired materials had a fine microstructure, but those containing 2.0 mol% Eu_2O_3 rapidly transformed from tetragonal into monoclinic cell upon cooling. The grain transformability in such polycrystals was dependent on the composition, because low doped samples had a critical grain-size for transformation, the lower the size the higher the content of Eu_2O_3. The ionic radius of the rare earth element used as a stabilizing oxide played an important role on the critical grain dimension for phase transformation. Eu^<3+> has a higher ionic radius than Er^<3+> but smaller than La^<3+>. Accordingly, also its critical grain size was smaller than in the case of erbia, but higher than that of lanthana.
社団法人日本セラミックス協会の論文
2000-06-01