FORMATION OF POINT DEFECTS IN CALCIUM TITANATE

The electrical conductivity and Seebeck coefficient of single crystal calcium titanate were measured as a function of temperature and PH2O{plus 45 degree rule}PH2. The electrical conductivity was determined at temperatures from 1100° to 1300°C. The PH2O{plus 45 degree rule}pH2 ratio extended from 2 × 10-4 to 8 × 10-2. At 1200°C the electrical conductivity was 3.70 Ω-1cm-1 at PH2O{plus 45 degree rule}PH2 = 10-3 and 1.75 Ω-1cm-1 at pH20{plus 45 degree rule}pH2 = 10-2; the Seebeck coefficients were - 500 and - 580μv°{plus 45 degree rule}k under the same conditions. The electrical conductivity was proportional to the -1 3 power of PH2O PH2. The sign of the Seebeck coefficient indicated the majority carriers to be electrons. The results may be described by a majority defect model consisting of doubly ionized oxygen vacancies and electrons. The standard enthalpy of formation was found to be 93,000 ± 4000 cal{plus 45 degree rule}mol. of oxygen vacancies. © 1969.