Development of zirconia-magnesia/zirconia-yttria composite solid electrolytes

Abstract

Composite solid electrolytes were prepared by thoroughly mixing ZrO2:8 mol% MgO (Z8Mg) and ZrO2:3 mol% Y2O3 (Z3Y) ceramic powders followed by pressing and sintering at 1500 °C/1 h. The properties of the sintered pellets were studied by X-ray diffraction for evaluation of the structural phases by the Rietveld method, by high-temperature dilatometry for analysis of the thermal shrinkage/expansion behavior, and by impedance spectroscopy for determination of the oxide ion conductivity. The x(Z8Mg) + (1 - x)(Z3Y) specimens, x = 0.2, 0.4, 0.5, 0.6, 0.8 and 1.0, are partially stabilized (monoclinic, cubic and tetragonal phases) with density > 94% of the theoretical density and show thermal shock resistance and electrical conductivity values suitable for high-temperature oxygen gas detection. One-end closed tube samples of the composite solid electrolytes were assembled in Pt/Z8Mg + Z3Y/Cr + Cr2O3/Pt electrochemical cells for exposure to different levels of oxygen in the 1-850 ppm range. The total electrical conductivity increases for increasing the relative Z3Y content. Addition of Z3Y to Z8Mg (80 wt.%-20 wt.%) suppresses the electronic contribution to the electrical conductivity at 620 °C.