Impedance spectroscopy was used to measure the conductivity of La1-x/2Y1-x/2CaxO3-α (x=0.1-10) at T=700-200оС and pH2O = 0.04-2.5 kPa. The bulk and grain boundaries conductivities were separated over the entire temperature range. It is found that the bulk and grain boundaries conductivities depend on the temperature and the wet of air.The highest proton conduction has been detected in the solid solution ofLa0.985Y0.985Ca0.03O3-α under wet air (pH2O=2.5kPa)
