Influence of magnesia doping on structure and electrical conductivity of pyrochlore type GdSmZr₂O

Polycrystalline ceramic samples of magnesia doped GdSm_1-xMg _xZr₂O_7-x/2 have been prepared by conventional solid state reaction method using high purity oxides. The influence of magnesia dopant content on densification, microstructure and electrical properties of GdSm_1-xMg_x Zr₂O_7-x/2 ceramics are investigated. Magnesia doping promotes the sintering densification behaviour of GdSm_1-xMg _xZr₂O_7-x/2 ceramics. GdSm_1-xMg_x Zr₂O_7-x/2 (X=0, 0.05, 0.10) ceramics have a single phase of the pyrochlore type structure, while GdSm_1-xMg _xZr₂O_7-x/2 (X=0.15, 0.20) ceramics consist of the pyrochlore type structure and a small amount of magnesia as the second phase. The total conductivity of GdSm_1-xMg_x Zr₂O _7-x/2 ceramics obeys the Arrhenius relation, and gradually increases with increasing temperature from 723 to 1173 K. GdSm_1-xMg_x Zr₂O_7-x/2 ceramics are oxide-ion conductors in the oxygen partial pressure range of 1.0X10^-4 to 1.0 atm at each test temperature. The maximum value of the total conductivity is 1.29X10^-2 S cm ^-1 at 1173 K for the GdSm_0.85Mg_0.15Zr₂O_6.925 ceramic.