The conductivity was deduced from the Warburg impedance at the lower end of a full impedance spectrum which was constructed by combining a partial spectrum, that had been measured directly using alternating-current impedance spectroscopy, with the Fourier-Laplace transform of the direct-current relaxation. In the tetragonal regime, the ionic conductivity was found to be essentially independent of the O partial pressure; with an activation energy of 2.46eV. It was also concluded that the conductivity in the orthorhombic regime was only slightly dependent upon the O partial pressure; with an activation energy of 1.58eV.

J.S.Lee, H.I.Yoo: Journal of the Electrochemical Society, 1995, 142[4], 1169-76