Microstructural characterization of partially stabilized and tetragonal zirconia solid electrolytes

Electron microscopy and frequency-dependent impedance data were used to stu dy the microstructure and electrical conductivity of fully (10 mol % Y2O3) and partially (3-5 mol % Y2O3) stabilized zirconia ceramics prepared by sol id-state reactions in vacuum at 2000 degrees C, followed by air annealing, and tetragonal ZrO2-Y2O3-Fe2O3 materials prepared via hydroxide coprecipita tion, followed by firing at 1400 degrees C. The phase composition of the sa mples was found to correlate with grain size, in agreement with previous st udies. The grain size of the tetragonal phase in partially stabilized zirco nia was shown to exceed the critical size, which is related to the particul arities of the heat-treatment conditions. The relative values of grain-boun dary and volume conductivities were shown to depend on the preparation proc edure.