The origin of the 500 nm luminescence band related to oxygen vacancies in ZrO2

In this paper, ion-beam-induced luminescence (IBIL) spectra of raw ZrO2 irradiated with 2 MeV H+ ions and photoluminescence (PL) spectra of annealed (200, 500 and 800 °C in air, nitrogen or oxygen) ZrO2 were investigated. The luminescence intensity decreased with increasing fluence, which indicated that the concentration of luminescence centers decreased during irradiation. The PL spectral results show that, with increasing partial pressure of oxygen during annealing, the intensity of luminescence decreases due to the decrease in oxygen vacancies. First-principles calculations were used to study the formation energy and transition level for oxygen vacancies (Vo), Ti-substituted Zr (Ti) and Ti adjacent to the nearest Vo (Ti-Vo) complex. The binding energies of Ti3+ and Vo + are 2.10 eV, which indicates that oxygen vacancies benefit the formation of Ti3+. The calculated configuration coordinate diagram and IBIL results indicated that Vo is not the luminescence origin. A new light-emitting structure of the Ti-Vo complex (FA center) structure was proposed based on our calculations and previous studies. The calculated results of the luminescence model match the PL and IBIL spectra remarkably. The emission band of ZrO2 at approximately 500 nm was assigned to the FA center or Ti3+ (the eg to t2g transition) adjacent to Vo+.