Effect of oxygen vacancy on phase transition and photoluminescence properties of nanocrystalline zirconia synthesized by the one pot reaction

Nanocrystalline ZrO₂ fine powders were prepared via the one-pot reaction followed by annealing from 700 to 1100 °C in air. It is believed that generation of excess oxygen vacancies within nanocrystalline ZrO ₂ is primarily responsible for room-temperature tetragonal phase stabilization below a critical size, and the phase transformation from tetragonal to monoclinic ZrO₂ happened in the annealing process. Luminescent properties of ZrO₂ were greatly affected by oxygen vacancies in the phase transition process. Two bands centered at 350 and 470 nm were observed in tetragonal ZrO₂. The electrons trapped by oxygen vacancies creating F centers recombined with holes yielding the 350 nm luminescence. Temporal decay of the 470 nm luminescence is due to the detrapping of electrons to the Ti³⁺ luminescence centers. Elevated temperature accelerated the phase transformation to monoclinic ZrO₂ and decreased the oxygen vacancy concentration, resulting in a decrease of the 350 nm emission and enhancement of the 470 nm phosphorescence.