Enthalpy of formation of Ba_0.5Sr_0.5Nb₂O₆

Ba_0.5Sr_0.5Nb₂O₆ is a quaternary oxide obtained from fission products in burning nuclear reactor. It has plenty of technological importance also due to its excellent intrinsic properties, such as ferroelectric-piezoelectricity, electro-optics properties etc. Thermodynamics plays an important role in predicting long term stability and formation of materials under different reactive conditions. The present paper describes determination of enthalpy of formation of Ba_0.5Sr_0.5Nb₂O₆ compound employing a high temperature solution calorimeter. The reaction enthalpies of MCO₃ (where M= Ba/Sr), Nb₂O₅(s) and Ba_0.5Sr_0.5Nb₂O₆(s) in liquid PbO + B₂O₃ solvent (2:1 molar ratios) at 966 K were measured. The value of Δ_fH°298 of Ba_0.5Sr_0.5Nb₂O₆ (s) from their elements was found to be -2503±4 kJ mol^-1. (author)