The ionic and electronic conduction of Gd0.95Ca0.05NbO4 was determined with ac conductivity measurements and impedance spectroscopy in combination with transport number measurements using the open circuit voltage (electromotive force) of concentration cells. Depending on the reaction conditions, protons, O ions, and electron holes were the main contributions to the total conductivity. The conductivity data were modeled according to a point-defect structure where the acceptor, Ca, was predominantly compensated by O vacancies and protons. Thermodynamic constants were derived for the hydration of the O vacancies and the transport properties of O ions, protons, and electron holes.

Ionic and Electronic Conductivity of 5%Ca-Doped GdNbO4. R.Haugsrud, B.Ballesteros, M.Lira-Cantú, T.Norby: Journal of the Electrochemical Society, 2006, 153[8], J87-90