Positron annihilation in β- and β'-vanadium oxide bronzes

Positron annihilation measurements in β-vanadium oxide bronzes using a long slit angular correlation apparatus with the fixed angle (θ=0deg) were performed. The dependencies of peak coincidence count rate on temperature in the range of 40 to 310degC were obtained for β-MxV2O5 bronzes with five different donor atoms: Li, Na, K, Cu, Ag. A three-states model corresponding to the annihilation of positrons in donor sublattice is applied for the description of the experimental data. The creation enthalpies of vacancies for this sublattice are compared with the activation energies of diffusion of donors obtained by means of galvanostatic pulse technique