Electrical Conduction in BaTiO3-δ in its Mixed n/p Regime Under Oxygen Potential Gradients

Electrical conduction under oxygen potential gradients was examined on single crystal BaTiO_3-δ in its mixed ion/electron/hole regime at 1000°C. The variation of current (I) vs. voltage (V) appears similar to that of an n/p junction, but with the limiting slope (dI/dV) approaching the maximum and minimum possible equilibrium conductance in the given oxygen potential gradient as increasing forward and reverse bias, respectively. This characteristic has been precisely traced theoretically by using the partial ionic and electronic conductivities of BaTiO_3-δ as measured against uniform oxygen activity in equilibrium state. The nonlinear characteristic is attributed to the redistribution of oxygen chemical potential that is caused by a non-vanishing gradient of the ionic transference number of the oxide under the given oxygen potential gradient.