Vaporization of Beryllium Oxide and Its Reaction with Tungsten

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Abstract
The composition of the vapor above beryllium oxide held in a tungsten Knudsen cell in the range 1900°‐2400°K has been determined mass spectrometrically. The vapor consists predominantly of Be and O atoms and (BeO)3 and (BeO)4 molecules. Smaller amounts of the following molecules were detected: O2, BeO, (BeO)2, (BeO)5, (BeO)6, WO2, WO3, and WOx·(BeO)y where x=1, 2 and y=1, 2, 3. A thermodynamic treatment of the data yielded a value of 4.6±0.1 ev for the dissociation energy of the BeO molecule. Heats of vaporization have been measured for the other (BeO)4 molecules and the data suggest a ring structure for these molecules. The boiling point of BeO has been crudely estimated as 3850±200°C at which temperature the vapor consists mostly of (BeO)4 and somewhat smaller amounts of (BeO)3 and (BeO)5. The atomization energies of the WO2 and WO3 molecules have been measured to be 13.6±0.4 ev and 19.3±0.4 ev, respectively. The dissociation energy of the WO molecule is estimated to be about 7.2 ev.