ENTHALPY INCREMENT MEASUREMENTS OF SR3ZR2O7(S) AND SR4ZR3O10(S)

Enthalpy increment measurements on Sr3Zr2O7(s) and Sr4Zr3O10(s) were c arried out using a Calvet micro-calorimeter. The enthalpy increment va lues were least squares analyzed with the constraints that H-o(T)-H-o( 298.15 K) at 298.15 K equals to zero and C-p(o)(298.15 K) equals to th e estimated value. The dependence of enthalpy increment with temperatu re can be given as: H-o(T) - H-o(298.15 K)(J mol(-1)) = 349.62 T(K) 7.621 x 10(-3) T-2(K) + 89.814 x 10(5)/T(K) -135 041(Sr3Zr2O7(s), 365. 4 less than or equal to T(K) less than or equal to 980.6) H-o(T) - H-o (298.15 K)(J mol(-1)) = 427.85 T(K) + 36.502 x 10(-3) T-2(K) + 81.679 x 10(5)/T(K) -158 203(Sr4Zr3O10(s), 365.4 less than or equal to T(K) l ess than or equal to 980.6) The first differential of the above equati ons with respect to temperature gives C-p(o)(T). Gibb's functions were evaluated using estimated S degrees(298.15 K) values. (C) 1998 Elsevi er Science S.A.