Proton Conduction in In[sup 3+]-Doped SnP[sub 2]O[sub 7] at Intermediate Temperatures

Abstract

-based proton conductors were characterized by Fourier transform infrared spectroscopy (FTIR), temperature-programmed desorption (TPD), X-ray diffraction (XRD), and electrochemical techniques. Undoped showed overall conductivities greater than in the temperature range of . The proton transport numbers of this material at under various conditions were estimated, based on the ratio of the electromotive force of the galvanic cells to the theoretical values, to be 0.97–0.99 in humidified and 0.89–0.92 under fuel cell conditions. Partial substitution of for led to an increase in the proton conductivity (from to at , for example). FTIR and TPD measurements revealed that the effects of doping on the proton conductivity could be attributed to an increase in the proton concentration in the bulk . The deficiency of ions in the bulk decreased the proton conductivity by several orders of magnitude, which was explained as due to a decrease in the proton mobility rather than the proton concentration. The mechanism of proton incorporation and conduction is examined and discussed in detail.