The structure and electrical properties of the palmierite Sr3P2O8

A 3 V 2 O 8 ( A = Ba, Sr) palmierite oxides are a novel and promising family of oxide ion conductors. Oxide ion conduction occurs through the formation and deformation of V 2 O 7 dimers while the proton migration takes place via proton hoping between O(1) sites and between O(1) and O(2) anions. Here, we show that the palmierite Sr 3 P 2 O 8 exhibits oxide ion conductivity. The conductivity is further enhanced under wet air compared to under a dry atmosphere, suggesting the possible contribution of both proton and oxide-ion conduction. Hence, palmierites with different cations on the B site, other than V 5+ , can exhibit ionic conductivity. However, the total conductivity at 600 °C under dry and wet air are 3.3 x 10 −8 S cm −1 and 8.9 x 10 −8 S cm −1 respectively which is more than two orders of magnitude less that that reported for Sr 3 V 2 O 8 . We suggest that this is a result of very short apical and equatorial P–O bond lengths in Sr 3 P 2 O 8 that limits the mobility of the oxide ion and reduces the oxide ion conductivity.