Proton and oxide-ion conduction in ZnO doped SnP2O7 ceramics

Abstract

A series of Sn1−xZnxP2O7 (x=0, 0.03, 0.06, 0.09, 0.12) ceramic samples have been prepared by a conventional solid state reaction method. The ceramic samples of x=0.00–0.09 exhibited a single phase structure, and the doping limit of Zn2+ in SnP2O7 was at least x=0.09. The conduction behaviors of the ceramic samples were investigated by means of electrochemical methods including AC impedance spectroscopy, isotope effect, gas concentration cells etc. in the temperature range of 300–650°C. Among the ceramic samples studied, the highest conductivities were observed for the Sn0.91Zn0.09P2O7 sample to be 1.69×10−4Scm−1 in wet air and 1.91×10−4Scm−1 in wet hydrogen at 600°C. Isotope effect confirmed the ceramic samples possessed proton conduction under water vapor-containing atmosphere. It was found that the sintering temperature of 1200°C in present investigation could result in not only appropriate densities, but also high conductivities of ceramic samples. It was also found that in wet hydrogen atmosphere Sn0.91Zn0.09P2O7 was almost a pure ionic conductor, the ionic conduction was contributed mainly to proton and partially to oxide-ion, whereas in wet air atmosphere, the ceramic sample exhibited a mixed ion and electron hole conduction.