The correlation of hydrogen diffusion with the relative concentrations of cubic and axial Fe3+ sites in KTaO3

Abstract

Hydrogen in the form of OH− ions has been incorporated into Fe-doped KTaO3 single crystals by heat treatments in H2O vapor, air, and hydrogen gas. Heat treatments in argon and oxygen resulted in a removal of OH− from the crystal. The conditions resulting in the incorporation of OH− also produced a decrease in the intensity of an axial Fe3+ EPR signal relative to the cubic site iron spectrum while the removal of OH− was accompanied by a relative increase in the axial EPR signal. The removal of oxygen from Fe-doped KTaO3 by heat treatments in potassium metal vapor was also found to elminate the axial Fe3+ EPR spectrum. These results do not support the previously accepted oxygen vacancy model for the Fe3+ axial site configuration and are contrary to the results of similar investigations of Fe3+ in SrTiO3.