Synthesis, sintering and transformability of chemically derived Eu2O3-ZrO2tetragonal solid solutions

Dense zirconia-europia tetragonal solid solutions were obtained by sinterin g nanometer-sized powders produced by coprecipitation from solutions of zir conyl and europium nitrates hydrates. The tetragonal phase could be retaine d at room temperature for compositions of 2.0-4.0 mol% Eu2O3, The fired mat erials had a fine microstructure, but those containing 2.0 mol% Eu2O3 rapid ly transformed from tetragonal into monoclinic cell upon cooling. The grain transformability in such polycrystals was dependent on the composition, be cause low doped samples had a critical grain-size for transformation, the l ower the size the higher the content of Eu2O3. 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. Eu3+ has a higher ionic radius than Er3+, but smaller than La3+. Accordingly, also its critical gra in size was smaller than in the case of erbia, but higher than that of lant hana.