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Mass-spectrometric study of the vaporization of Li2O(s) and thermochemistry of gaseous LiO, Li2O, Li3O, and Li2O2

1978; Elsevier BV; Volume: 78; Issue: 2 Linguagem: Inglês

10.1016/0022-3115(78)90460-9

1873-4820

Hiroshi Kudo, C.H. Wu, H.R. Ihle,

Nuclear Materials and Properties

The equilibrium vapor pressures over solid lithium oxide (Li2O) have been measured mass-spectrometrically using platinum Knudsen cells in the temperature range 1300–1700 K. From the gaseous equilibria the heats of formation of LiO(g), Li2O(g), Li3O(g), and Li2O2(g) were determined as follows: ΔH00(LiO) = 8.3 ± 3.3 kcal/mol, ΔH00(Li2O) = − 42.3 ± 1.1 kcal/mol, ΔH00(Li3O) = −48.4 ± 5.6 kcal/mol, and ΔH00(Li2O2) = −71.5 ± 7.4 kcal/mol. The atomization energies are D00D00(LiO) = 89.2 ± 3.3 kcal/mol, D00(Li2O) = 178.3 ± 1.1 kcal/mol, D00(Li3O) = 222.9 ± 5.6 kcal/mol, and D00(Li2O2) = 266.5 ± 7.4 kcal/mol. The relation D00(LiO) = D00(Li-OLi) is derived here. The bond dissociation energy D00(Li-Li2O) is 44.6 ± 5.5 kcal/mol. In addition, the vaporization of Li2O has been studied by using molybdenum, tantalum and graphite Knudsen cells in the temperature range 1200–1500 K to measure the distribution of the partial pressures under these conditions. It was found, for example, that due to the reaction of Li2O with the wall of a molybdenum cell, their partial pressure of Li3O, which was detected as a stable molecule for the first time, was increased by about a factor of 10 compared with its pressure measured in a platinum cell.