Hole-Trapping in ATiO₃, (A = Ba, Sr, Ca)

Measurements of the equilibrium oxygen activity as a function of temperature at constant defect concentrations have been used to obtain the chemical enthalpy of oxidation, i.e. the reaction to add a stoichiometric excess of oxygen and trapped holes, for acceptor-doped BaTiO₃, SrTiO₃, and CaTiO₃. The values are −0.15, +0.21, and −0.28 eV, respectively. Combined with the enthalpy of oxidation obtained from equilibrium conductivity measurements, i.e. the reaction to form free holes, the depths of the acceptor hole traps are found to be 0.54, 0.60, and 1.22 eV, respectively.

Keywords:

• Perovskites
• defects
• conductivity
• hole-traps

Acknowledgment

The authors appreciate the support of the Division of Materials Research of the National Science Foundation.