Standard Gibbs energy of formation of tellurium dioxide measurement by a solid-oxide electrolyte EMF technique

•An improved experimental apparatus and new data analysis method have been applied.•Galvanic cells including solid zirconia electrolyte were measured accurately.•ΔfG° values for TeO2 have been determined in wide temperature range.•Third law plots for S298° and ΔH298° of TeO2 were produced using the experimentally observed values.

The standard Gibbs energy of formation of TeO2 in the temperature range 369–795 °C was measured by the EMF method involving solid-oxide electrolyte galvanic cells of the type:(−)Pt, Ir, Te(s, l), TeO2(s, l)|YSZ|O2, Pt(+),where YSZ denotes stabilized zirconia with 8.5 mass percent of yttrium oxide. The standard Gibbs energies of formation obtained from the above cells are linear functions of temperature as:ΔfG° (kJ/mol) = −317.09 + 0.180 T (K) ± 0.307 (642–722.15 K) both phasess are solid.ΔfG° (kJ/mol) = −318.01 + 0.181 T (K) ± 0.308 (722.15–1005.8 K) Te – liquid; TeO2 – solid.ΔfG° (kJ/mol) = −256.26 + 0.120 T (K) ± 0.226 (1005.8–1068 K) both phases are liquid.