Defect Structure and Electrical Properties of Single‐Crystal Ba 0.03 Sr 0.97 TiO 3

The electrical conductivity and thermoelectric power of single‐crystalline Ba 0.03 Sr 0.97 TiO 3 were measured over a wide temperature (800° to 1100°C) and oxygen partial pressure (10 5 to 10 ‐15 Pa) range. Our experimental data, like those of previous workers on nominally undoped BaTiO 3 or SrTiO 3 , support a defect model based on doubly ionized oxygen vacancies, electrons, holes, and accidental acceptor impurities. The simultaneous measurement of electrical conductivity and thermoelectric power, together with precise experimental data obtained with an advanced thermoectric power measurement technique, enabled us to determine for the first time reliable values for the preexponential factors and the activation energies which characterize the defect equilibrium constants. These calculated values, together with the defect model, were found to give an excellent fit to the experimental data, and were used to generate the boundaries, in P o2 ‐1/ T space, of the various defect regimes.