Enthalpies of Formation of SrPbO3 and Sr2PbO4

Published

December 1, 2002

Author(s)

R Klein, Lawrence P. Cook, Winnie K. Wong-Ng

Abstract

Alkaline-earth plumbates are important accessory phases in (Bi,Pb)-Sr-Ca-Cu-O (BSCCO) high temperature superconductor materials. Reliable values for standard enthalpies of formation (D f H o) of the plumbates are therefore an essential part of the BSCCO high temperature superconductor themodynamic data base. To obtain D f H o of SrPbO3 and Sr2PbO4, we measured the heats of solution of SrO, PbO2, SrPbO3, and Sr2PbO4 in 6M HCl by isoperibol solution calorimetry and derived the values of D f H o for the strontium plumbates using Hess cycles. The values obtained were D f H oSrPbO3 (298.15 K) = -949.3 3.5 kJ/mol and D f H oSr2PbO4 (298.15 K) = -1565.1 6.9 kJ/mol. In previous experiments, we measured total vapor pressures over SrPbO3 using Knudsen effusion vacuum thermogravimetry. In the present paper, these data were used for an independent derivation of D f H oSrPbO3(298.15 K) via a van't Hoff extrapolation, which yielded -945.8 7.5 kJ/mol, in reasonable agreement with the value obtained calorimetrically. Our determination of D f H oSr2PbO4(298.15) agrees well with a recently published value obtained from electrochemical measurements, but differs from earlier published calorimetric determinations.

Citation

Journal of Chemical Thermodynamics

Volume

34

Issue

No. 12

Pub Type

Journals

Keywords

enthalpy of formation, high temperature, knudsen effusion, PBO pressure, solution calorimetry, Sr₂PbO₄, SrPbO₃, strontium plumbate, superconductor

Citation

Klein, R. , Cook, L. and Wong-Ng, W. (2002), Enthalpies of Formation of SrPbO₃ and Sr₂PbO₄, Journal of Chemical Thermodynamics (Accessed October 31, 2024)