Proton Solubility in Undoped and Fe-doped SrTiO3: Temperature Dependence and Formation of Defect Associates

Abstract

The temperature dependence of the solubility of proton defects in SrTiO3 single crystals was investigated by IR spectroscopy. Based on the integrated absorption of the OH stretching vibration bands, the enthalpies of the dissolution reaction were determined for undoped and Fe-doped SrTiO3. In contrast to undoped SrTiO3, which shows only one unique OH absorption frequency, characteristic sidebands were observed for Fe-doped crystals. These sidebands were attributed to the formation of associates between donor-type proton defects and Fe-acceptors in the perovskite lattice. From the temperature dependence of the sideband absorptions, an association enthalpy was estimated. The proton solubility and the sidebands were not affected by changing the oxygen partial pressure between approx. 10-15 and 105 Pa.