Sintering and conductivity of nano-sized yttria-doped ZrO2 synthesized by a supercritical CO2-assisted sol-gel process

Abstract

This study reports on the electrical characterization of nano-sized zirconia powders doped with 3 and 8mol% Yttria, referred to as 3Y-ZrO2 and 8Y-ZrO2, respectively. Powders were synthesized using a supercritical CO2 assisted sol-gel method to control the size and morphology of the powder particles. Spark plasma sintering (SPS) was used to sinter the powders and maintain a fine microstructure with small grain size. The microstructure and chemical composition of the resulting ceramics was evaluated by electron microscopy techniques, showing grain boundaries depleted of amorphous phase. Electric conductivity of the 8Y-ZrO2 pellets was determined by electrochemical impedance spectroscopy techniques, between 200 and 800°C, and correlated with the microstructure. The bulk electric response at 300°C is comparable to commercially available Y-ZrO2 compositions. Compared to conventionally prepared samples we obtain lower conductivity in the high temperature range, still values in this study are twice superior to 3Y-ZrO2 samples similarly prepared by SPS.