Internal friction in ceria ceramics doped with alkali earth metal oxides

Abstract

Ceria and 5 mol% of alkali earth metal powder were fired at 1673 K for 6 h in air in order to prepare specimens containing a solid solution of ceria and alkali earth metal oxide. The internal friction as a function of temperature shows a peak at around 450 K. The internal friction peak intensity observed is strongly dependent on the kind of dopant cation. The peak for ceria doped with CaO was the largest, whereas the peak for ceria doped with BaO was the smallest. The ion motion and structures have been analysed by molecular dynamics calculations using as pair potential the Busing approximation of the Born-Mayer-Huggings type. The directions of motion and velocity distributions of dopant cations and oxygen ion vacancies formed by addition of alkali earth metal oxide tend to unidirectional motion and sharp distributions when the ionic radius of the dopant cation is larger or smaller than that of the cerium ion. It is concluded that the internal friction peaks depend on the direction of motion and velocity distribution of the ions.