Lifetime Spectra of Positrons in (Ba_{1-1.5<i>x</i>}Gd\(_{x}\square_{0.5x}\))TiO₃

Abstract

Positron lifetime spectra were measured at 20°C in Gd-doped BaTiO 3 which contained a large amount of Ba 2+ vacancies. It was found that the intensity of long-lived (τ 2 ) component was proportional to the nominal vacancy concentration and the averaged annihilation rate decreased as the concentration increased. To explain the observed results a model is proposed in which most of Ba 2+ vacancies form pairs with Gd 3+ and these pairs attract, but do not trap positrons, and isolated Ba 2+ vacancies trap positrons giving τ 2 component.