A knudsen cell-mass spectrometer study of the vaporization of cesium telluride and cesium tellurite

Abstract

Vapour pressures of cesium telluride, Cs 2Te, and of cesium tellurite, Cs 2TeO 3, were measured as a function of temperature from 600 to 1000 ° C using a Knudsen cell technique with a quadrupole mass spectrometer as the detector for gaseous species. Standard enthalpies of vaporization were measured for Cs, Te, Te 2, Te 3, CsTe and Cs 2Te from Cs 2Te, and for Cs from Cs 2TeO 3. All were in the range of 147 + 9 kJ mol −1. Absolute vapour pressures were measured using silver as a standard. From these vapour pressures, standard Gibbs energies of vaporization for Cs and Te were 99.7 and 110.0 kJ mol −1 from Cs 2Te, and 116.9 and 133.4 kJ mol −1 from Cs 2TeO 3. The values for Cs 2Te are in good agreement with thermodynamic measurements reported recently. Difficulties in calibrating the mass spectrometer prevented the accurate determination of absolute vapour pressures for species with molecular weight much above 300.