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Positron Annihilation in Off-Stoichiometric and Ta-Doped Zn2TiO4


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While Zn vacancies are regarded as the charge compensators in Ti-rich Zn2TiO4, no evidence of cation vacancies in essentially single-phase samples containing up to 13 wt% excess TiO2 was evident from positron annihilation lifetime spectroscopy (PALS). Nor was there strong evidence of cation vacancies in Ta-doped samples targeted to contain either tetrahedral or octahedral vacancies, although there was a small increase in the lifetime as the doping level increased and the structure changed from cubic to tetragonal.