Grain Growth of Micron-Sized Grains in Undoped and Cobalt Oxide Doped Ceria Solid Solutions

Abstract

Isothermal grain growth experiments have been conducted for undoped as well as cobalt oxide doped CeO₂ and Ce_0.8Gd_0.2O_1.9 (CGO20). Due to the solute drag effect of the dissolved gadolinium ions, the grain boundary mobility of CGO20 was significantly lower than that one of CeO₂. The addition of cobalt oxide increases the grain boundary mobility of CGO20. This increase is assigned to the formation of a characteristic cobalt oxide rich grain boundary film. In undoped and cobalt oxide doped CGO20, a transition from regular grain growth at high temperature in micron-sized grains to self-limited grain growth at low temperature in nanometer-sized grains occurs. As a consequence, highly stable microstructures result at lower temperatures. It is suggested that strain in amorphous grain boundary films becomes important for the self limited grain growth for very small grains at low temperatures.