Positron Lifetime in the Atomic Vacancies of Nonstoichiometric Titanium and Vanadium Carbides

Identification and study of vacancies in titanium monoxide by means of positron annihilation techniques

“…12 This supposition was supported thereafter by irradiation experiments. 13,14 The valence electron density in a titanium vacancy of titanium monoxide has been studied by means of positron lifetime spectroscopy because positrons are trapped exclusively on the titanium sublattice and the positron lifetime is a measure for the valence electron density at the positron annihilation site. In Fig.…”

“…3 one can see the linear behavior of the positron lifetime t in a single atomic vacancy versus the mean atomic and vacancy volume O in nonstoichiometric titanium monoxides measured in this work and in titanium carbides measured in ref. 14 and niobium carbides measured in ref. 12.…”

“…The linear behavior with positive coefficient between the positron lifetime and the volume of the vacancy found in titanium and niobium carbides could be explained by the same charge and different volume of the carbon vacancy in these carbides. 12,14 Indeed, each carbon vacancy independently from carbides composition has 6 metal atoms as nearest-neighbors. The variation of the composition leads as a first approximation exclusively to a variation of the vacancy volume.…”