Vaporization, thermodynamics and structures of species in the tellurium + oxygen system

Abstract

High-temperature mass-spectrometric investigations of the equilibrium vapours over crystalline tellurium dioxide have shown the existence of the molecular species (TeO₂)_n and (TeO)_n, where n= 1, 2, 3, 4 as well as Te₂ and O₂. Under these conditions the most abundant species are TeO₂(g) and TeO(g). Second- and third-law heats of reaction and entropies for the various equilibria among these species have been obtained. Fundamental frequencies obtained from infra-red absorption studies of the species isolated in rare-gas matrices were used for calculations of thermodynamic functions at various temperatures. Heats of atomization for (TeO₂)₂ and (TeO)₂ were obtained. Using the average of the second and third-law heats, ΔH°₂₉₈= 2.5 ± 2 kcal mol^–1, for the reaction TeO(g)=½Te₂(g)+½O₂(g) one obtains the dissociation energy for TeO(g), D°₀= 92.5 ± 2 kcal mol^–1. A bent geometry (110°) is indicated for TeO₂ and evidence for cyclic structures of (TeO₂)₂ and (TeO)₂ is given.