Proton and oxide-ion conduction in ZnO doped SnP2O7 ceramics

Highlights: ► A novel series of Sn1−xZnxP2O7 ceramics samples have been prepared by solid state reaction method. ► The highest conductivities were observed for Sn0.91Zn0.09P2O7 to be 1.69 × 10−4 S cm−1 in wet air and 1.91 × 10−4 S cm−1 in wet hydrogen at 600 °C. ► The suitable sintering temperature in this study was 1200 °C, which resulted in not only appropriate densities, but also high conductivities of ceramic samples. ► In wet hydrogen, Sn0.91Zn0.09P2O7 was almost a pure ionic conductor. ► In wet air, Sn0.91Zn0.09P2O7 was a mixed ion and electron hole conductor. - 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 × 10−4 S cm−1 in wet air and 1.91 × 10−4 S cm−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.