Thermodynamic Properties for Nd2(MoO4)3 Formed in the Nuclear Fuel Waste Glasses

The thermodynamic properties for Nd-2(MoO4)(3) were investigated. Nd-2(MoO4)(3) is one of the end member of the yellow phases which are known as hygroscopic harmful phases in the nuclear fuel waste glasses. The standard molar entropy,Delta S-T(0)degrees(m), at 298.15 K of Nd-2(MoO4)(3) was determined by measuring its isobaric heat capacities, C degrees(p,m), from 2 K via the fitting functions including the Debye-Einstein formula and electronic-as well as magnetic terms. The Neel temperature, T-N, estimated by extrapolating the magnetic- term in the fitting function. Its standard Gibbs energy of formation,Delta(f)G degrees(m), was determined by combining.Delta S-T(0)degrees(m). datum with the standard enthalpy of formation,Delta H-f degrees(m), which were estimated from ones for Ce-2(MoO4)3 and Sm-2(MoO4)(3). The unknown standard Gibbs energies of solution,Delta(sln)G degrees, at 298.15 K for Nd-2(MoO4)(3) were predicted from the reference data for MoO42-(aq) and Nd3+(aq). The obtained thermodynamic values are as follows: Delta S-T(0)degrees(m)(Nd-2(MoO4)(3), 298.15K) / (JK(-1)mol(-1))=439.38 +/- 4.39 Delta(f)G degrees(m)(Nd-2(MoO4)(3), 298.15K) / (KJ mol(-1))=4072.38 +/- 12.7 Delta(sln)G degrees(Nd-2(MoO4)(3),(cr), 298.15K) / (KJ mol(-1))=219.1 +/- 13.7 T-N/ K=1.43 +/- 0.14