Gibbs energy of formation of solid Ni3TeO6 from transpiration studies

Abstract The thermodynamic stability of nickel tellurate was established by studying the heterogeneous equilibrium Ni 3 TeO 6 ( s )=3 NiO ( s )+ TeO 2 ( g )+ 1 2 O 2 ( g ) . Using the transpiration technique, the equilibrium constant of the reaction was obtained from the vapor pressure measurement of TeO2(g) over the biphasic mixture of Ni3TeO6(s) and NiO(s) under 1 bar oxygen pressure. From the equilibrium data the second-law value of ΔfH° (Ni3TeO6(s), 298.15 K) was found to be −1216(±14) kJ mol−1. The energy change of the heterogeneous reaction derived from the equilibrium constant was used to calculate the Gibbs energy of formation of Ni3TeO6 as could be expressed by ΔfG° (Ni3TeO6(s)) (±13 kJ mol −1 )=−1307+0.64· T , ( 1122 K ⩽T⩽1202 K ). The above Gibbs energy data were found to be consistent with the available thermodynamic information of the Ni–Te–O ternary system.