Oxide ion conductivity in doubly doped PrGaO3 perovskite-type oxide

In this study, oxide ion conduction characteristics of doubly doped PrGaO3 were investigated. St is found that PrGaO3 doped with Sr (or Ca) for the Pr site and Mg for the Ga site exhibits the high oxide ion conduction which w as slightly less than that measured for doubly doped La(Sr)Ga(Mg)O-3 (LSGM) . Doping alkaline earth cations for the Pr site and Mg for the Ga site of t he PrGaO3 increased its oxide ion conductivity. For temperatures above 1073 K, the highest oxide ion conductivity was obtained for the composition of Pr0.93Sr0.07Ga0.85Mg0.15O3 (PSGM). On the other hand, the apparent activati on energy of Pr0.93C0.07Ga0.85Mg0.15O3 (PCGM) was as low as 0.65 eV. Theref ore, the electrical conductivity of PCGM was higher than that of LSGM at te mperatures below 873 K. Although hole conduction was observed, electron con ductivity of the doubly doped PrGaO3 was almost independent of the oxygen p artial pressure from p(O2) = 1 to 10(-21) atm. It is clear that doped PrGaO 3 is a new fast oxide ion conductor over a wide range of oxygen partial pre ssures. On the other hand, a nonlinearity was observed on the Arrhenius plo t of electrical conductivity for Ca-doped PrGaO3 and the high temperature X -ray diffraction (XRD) measurement suggested that it was due to phase trans ition from orthorhombic to rhombohedral or tetragonal, which may decrease t he mobility of oxide ions. Application of PSGM and PCGM for an electrolyte of solid oxide fuel cell was also investigated in order to cross-check the findings of the fast oxide ion conductivity. This study revealed that PSGM and PCGM were a new family of fast oxide ion conductors. (C) 1999 The Elect rochemical Society. S0013-4651(98)08-041-0. All rights reserved.