ENTHALPY INCREMENTS OF STRONTIUM AND BARIUM ZIRCONATES

Enthalpy measurements on SrZrO3(s) and BaZrO3(s) were carried out usin g a Calvet micro-calorimeter. The increase in enthalpies with temperat ure were analyzed by least squares with the constraint that H-0(T) - H -0 (298.15 K) at 298.15 equals zero and C-p(0) (298.15 K) equals the l iterature value. The dependence of enthalpy on temperature was: H-0(T) - H-0(298.15 K)(J/mol) = 126.62T(K) + 5.478 x 10(-3)T(2)(K) + 23.553 x 10(5)/T(K) - 46138 (SrZrO3(s)) H-0(T) - H-0(298.15 K)(J/mol) = 128.5 3T(K) + 2.571 x 10(-3)T(2)(K) + 25.204 x 10(5)/T(K) - 47003 (BaZrO3(s) ) The first differential of the above equations with respect to temper ature gave C-p(0)(T). Gibbs free energy functions were evaluated using S-0(298.15) values from the literature. (C) 1997 Elsevier Science B.V .