Thermo physico-chemical investigations on A–Te–O (A = Cr, Fe, Ni) system

•Heat capacity of Cr2TeO6 (s), Fe2TeO6 (s) and Ni3TeO6 (s) were measured.•Thermal expansion and Gibbs energy of formation of Fe2TeO6 (s) and Ni3TeO6 (s) were measured.•Enthalpy of formation of AnTeO6 (s) (where A = metal atom, n = 2, 3 or 6) was estimated.•Heat capacity of TeO3 (s) was estimated.•Chemical potential diagram was generated for A–Te–O system (A = Fe,Cr,Ni).

The compounds, Cr2TeO6 (s), Fe2TeO6 (s) and Ni3TeO6 (s) were synthesized by solid-state route and characterized using X-ray diffraction technique. Thermal expansion of Fe2TeO6 (s) and Ni3TeO6 (s) were studied by high temperature X-ray diffraction technique in the temperature range 298–973 K and 298–923 K, respectively. The average volume thermal expansion coefficient of Fe2TeO6 (s) and Ni3TeO6 (s) were determined to be 2.46 × 10−5 and 3.02 × 10−5 K−1, respectively. Heat capacity of Cr2TeO6 (s), Fe2TeO6 (s) and Ni3TeO6 (s) was measured, in the temperature range of 300–870 K, employing temperature modulated differential scanning calorimeter. The Gibbs energy of formation of Fe2TeO6 (s) and Ni3TeO6 (s) were measured using transpiration method. An empirical function was derived to compute enthalpy of formation of AnTeO6 (s) (where A = various elements of periodic table, n = 2, 3 or 6). Self consistent thermodynamic functions of Cr2TeO6 (s), Fe2TeO6 (s) and Ni3TeO6 (s) were calculated. The chemical potential diagrams of A–Te–O (A = Cr, Fe, Te) system were also constructed.