Intermediate temperature ionic conduction in Sn1−xGaxP2O7

A novel series of samples Sn1−xGaxP2O7 (x = 0.00, 0.01, 0.03, 0.06, 0.09, 0.12, 0.15) are synthesized by solid state reaction. XRD patterns indicate that the samples of x = 0.00 − 0.09 exhibit a single cubic phase structure, and the doping limit of Ga3+ in Sn1−xGaxP2O7 is x = 0.09. The protonic and oxide-ionic conduction in Sn1−xGaxP2O7 are investigated using some electrochemical methods at intermediate temperatures (323–523 K). It is found that the samples exhibit appreciable protonic conduction in hydrogen atmosphere, and a mixed conduction of oxide-ion and electron hole in dry oxygen-containing atmosphere. The highest conductivities are observed for the sample of x = 0.09 to be 4.6 × 10−2 S cm−1 in wet H2 and 2.9 × 10−2 S cm−1 in dry air at 448 K, respectively. The H2/air fuel cell using x = 0.09 as electrolyte (thickness: 1.45 mm) generates a maximum power density of 19.2 mW cm−2 at 423 K and 22.1 mW cm−2 at 448 K, respectively.