The electrical conductivity of LaP3O9 doped with 1mol% of divalent metals (Ca, Sr, and Ba) substituting La was investigated at pH2O = 0.1 to 5kPa, pO2 = 0.01 to 100kPa and 573 to 973K. The H/D isotope effects, proton transport number measurements, and independence of conductivity upon pO2 showed that acceptor-doped LaP3O9 exhibited predominantly proton conduction. The conductivity was largely independent of pH2O at constant temperature, indicating that the acceptor was charge compensated by protons and exhibited protonic conduction even at low pH2O. The conductivities depended considerably upon the dopant species and increased in the order: Ca < Ba < Sr.

Protonic Conduction in Acceptor-Doped LaP3O9. K.Amezawa, Y.Kitajima, Y.Tomii, N.Yamamoto, M.Widerøe, T.Norby: Solid State Ionics, 2005, 176[39-40], 2867-70