Thermodynamics of formation of two cerium aluminum oxides, CeAlO3(s) and CeAl12O19.918(S), and cerium sesquioxide, Ce2O3(s) at T=298.15 K

Oxides containing cerium are of great interest in the chemistry of modem la mp materials as well as being surrogates for materials containing plutonium in the development of ceramic nuclear waste materials. Using high temperat ure oxide-melt solution calorimetry, the molar enthalpies of drop solution Delta(298.15 K)(T) H-m(sol) of CeO2(s), CeAlO3(s), and CeAl12O19.918 (s) in molten lead berate solvent (2PbO . B2O3) have been measured at T = 973 K a nd are (122.9 +/- 2.6) kJ . mol(-1), (62.31 +/- 0.80) kJ . mol(-1), and (63 1.7 +/- 2.8) kJ . mol(-1), respectively. The standard molar enthalpies of f ormation from the elements Delta(f)H(m)(o) for CeAlO3 (s) and CeAl12O19.918 (s) are -(1806.6 +/- 3.1) kJ . mol(-1) and - (11001.8 +/- 9.5) kJ . mol(-1 ), respectively, at T = 298.15 K. The Delta(f)H(m)(o), of Ce2O3 (s) is -(18 05.8 +/- 5.8) kJ . mol(-1) at T = 298.15 K. It is suggested that CeAl12O19. 918 (s) is an entropy-stabilized material. (C) 2000 Academic Press.