Monocrystalline samples of La1-xCaxAlO3, where x was between 0.0027 and 0.008, were prepared by using a float-zone technique. The conductivity and the O non-stoichiometry were measured by using a direct-current 4-probe method and high-temperature gravimetry, respectively, as a function of O partial pressures of between 1 and 10-20atm and temperatures of up to 1100C. It was found that the non-stoichiometric change in the O content, as a function of O partial pressure and temperature, was smaller than the experimental error (0.001). The results were analyzed by using a simple defect model which assumed that CaLa', and Vo• were the predominant defects and that electron holes were minor defects. The conductivities which were due to electron holes and O vacancies, at temperatures of between 700 and 1000C, were found to be described by the equations:

h (S/cm) = 35x½PO2¼exp[-0.56(eV)/kT]

and

v (S/cm) = 2.0 x 105(x/T)exp[-0.74(eV)/kT]

respectively. The O vacancy diffusion coefficient was described by:

Dv (cm2/s) = 0.0029 exp[-0.74(eV)/kT].

J.Mizusaki, I.Yasuda, J.Shimoyama, S.Yamauchi, K.Fueki: Journal of the Electrochemical Society, 1993, 140[2], 467-71