Influence of magnesia doping on structure and electrical conductivity of pyrochlore type GdSmZr ₂O ₇

Polycrystalline ceramic samples of magnesia doped GdSm _1-xMg _xZr ₂O _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 _xZr ₂O _7-x/2 ceramics are investigated. Magnesia doping promotes the sintering densification behaviour of GdSm _1-xMg _xZr ₂O _7-x/2 ceramics. GdSm _1-xMg _xZr ₂O _7-x/2 (x50, 0.05, 0.10) ceramics have a single phase of the pyrochlore type structure, while GdSm _1-xMg _xZr ₂O _7-x/2 (x50.15, 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 _xZr ₂O _7-x/2 ceramics obeys the Arrhenius relation, and gradually increases with increasing temperature from 723 to 1173 K. GdSm _1-xMg _xZr ₂O _7-x/2 ceramics are oxide-ion conductors in the oxygen partial pressure range of 1.0×10 ^-4 to 1.0 atm at each test temperature. The maximum value of the total conductivity is 1.29×10 ^-2 S cm ^-1 at 1173 K for the GdSm _0.85Mg _0.15Zr ₂O _6.925 ceramic.