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.