Abstract
Positron lifetime and Doppler broadened lineshape parameter have been measured as a function of quench temperature in Y1Ba2Cu3O7-x. The mean lifetime, 
, and the peak parameter of the Doppler broadened lineshape, I, are observed to decrease as the quench temperature (TQ) is lowered from 925 °C to 325 °C. The variations in and I with TQ are observed to correlate with the oxygen deficiency (x) measured at a various quench temperatures. The positron lifetime component, τ2, attributed to trapping at oxygen vacancies, is observed to decrease from (200 ± 1) ps in the tetragonal phase (x = 0.5) to (190 ± 1) ps in the orthorhombic phase (x = 0.0). The variation in positron annihilation parameters with TQ is qualitatively explained in terms of a change in the charge state of oxygen vacancies.