Proton conductivity and mobility in Sr-doped LaScO3 perovskites

In this work, we set out to investigate the electrical conductivity of single-phase and high-density La1-xSrxScO3-δ (x = 0.05; 0.1) ceramics depending on temperature and рО2 and рН2О. The crystal structure of materials was characterized by XRD method. The samples show the structure of an orthorhombic perovskite with a Pnma space group. The unit cell volume increases along with the Sr concentration. The microstructure features of samples were investigated by SEM analysis. The transference numbers of protons and oxygen-ions were determined by the EMF (electromotive force) measurements in a gas concentration cell. In addition, the proton, oxygen-ion and hole conductivities were evaluated from the рО2-dependencies of electrical conductivity at different humidity. The results obtained using both methods showed a good level of agreement. It is found that the partial conductivity of each charge carrier in La1-xSrxScO3-δ increases along with an increase in the concentration of the Sr dopant from x = 0.05 to x = 0.1. The highest proton conductivity about 3 × 10−2 S cm−1 is achieved for La0·9Sr0.1ScO3-δ at 800 °C. The mobility of proton defects increases with Sr concentration and reaches 2.5 × 10−4 cm2 V−1 s−1 at 800 °C for La0·9Sr0.1ScO3-δ. Thus, La0·9Sr0.1ScO3-δ should be considered as a promising proton-conducting electrolyte for various electrochemical devices, such as protonic ceramic fuel cells.