Samples of La1-xSrxPO4 having the nominal compositions, x = 0.025 or 0.050, were prepared by powder combustion synthesis, cold-pressing and sintering at 1300C. Samples with Pt paste electrodes were characterized by conductivity measurements, impedance spectroscopy and transport number measurements. The samples were mainly protonic conductors below 700C in wet O, as proven for the first time using the EMF/water vapor concentration cell method. Modeling of the conductivity data over a large temperature range suggested that the entropy and enthalpy changes of the incorporation of water vapor to hydrolyze the P2O74- group into two HPO42- groups were -90J/molK and -83kJ/mol, respectively. Impedance spectroscopy showed that grain boundary resistance was predominant only below 400C. The synthesis procedure was convenient, but the proton conductivity appeared to be lower than that reported elsewhere. This was partly attributed to insufficient dopant homogenization.

Impedance Spectroscopy and Proton Transport Number Measurements on Sr-Substituted LaPO4 Prepared by Combustion Synthesis. S.Gallini, M.Hänsel, T.Norby, M.T.Colomer, J.R.Jurado: Solid State Ionics, 2003, 162-163, 167-73