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The Thermochemical Behaviour of Te8O10(PO4)4 and its Use for Phosphide Telluride Synthesis 



    Dedicated to Professor Heinrich Oppermann on the Occasion of His 75th Birthday


The tellurium oxide phosphate Te8O10(PO4)4 was synthesised by thermal decomposition of Te2O3HPO4 at temperatures above 400 °C. Te8O10(PO4)4 melts at 570 °C and evaporates at 820 °C. The thermodynamic standard data were determined by solution calorimetry and differential scanning calorimetry and were optimised by thermodynamic modelling of the binary system TeO2/P2O5: ΔH{}^0_298[Te8O10(PO4)4] =–5844(2) kJ·mol–1; S{}^0_298[Te8O10(PO4)4] = 823.3 J·mol–1·K–1. The phase relations in quaternary systems M/P/Te/O (M = Ti, Zr, Ce) were calculated and optimised synthesis parameters for phosphide tellurides were derived.

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