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 degrees C in air. It is believed that generation of excess oxygen vacancies within nanocrystalline ZrO2 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 urn emission and enhancement of the 470 nm phosphorescence.