First-principles study on the optical spectra of ZrO₂ crystal with oxygen vacancy

Abstract

In this paper, we present the optical spectra of the ZrO2 crystal containing oxygen vacancy based on the Density Functional Theory (DFT). The finite-size correction scheme (FNV) is employed to eliminate the artificial interactions and correct the defect formation energy of oxygen vacancies with three different charges (0, +1, +2). Besides, we use hybrid density functionals to relieve the band edge problem. Finally, we obtain the optical spectra for the F center and F[Formula: see text] center containing the electron–phonon coupling. The absorption peak of F center of threefold coordinate oxygen vacancy (V[Formula: see text]) near 446 nm (2.78 eV) agrees well with the experimental value (2.83 eV), which can enhance the visible light photocatalytic ability of ZrO2. The luminescence peak of the F[Formula: see text] center of fourfold coordinate oxygen vacancy (V[Formula: see text]) is 561 nm (2.21 eV), which is close to the experimental value (2.5 eV).

Unraveling the Charge State of Oxygen Vacancies in Monoclinic ZrO2 and Spectroscopic Properties of ZrO2:Sm3+ Phosphor

“…The obtained bond distances compare well with the previous theoretical and experimental results reported in the literature, except for the d3 and d7 bonds. The distances between oxygen vacancies and neighboring Zr atom values of 2.256 and 0.276 Å match with d3 (2.213 Å) and d7 (2.269 Å) bond distances, respectively …”

“…In order to support this argument, the following points are considered: (i) first, the Zr–O1 (d3) and Zr–O2 (d7) bond distance matches with the distance between oxygen vacancies and Zr atoms. According to first-principles calculations, the luminescence of the F + center of threefold and fourfold coordinate oxygen vacancy (O1 and O2) in monoclinic ZrO 2 is expected at 610 and 561 nm, respectively . (ii) Second, the EPR signal at g = 1.99 is a characteristic of oxygen vacancies.…”

“…However, the presence of Ti 3+ ions in monoclinic ZrO 2 is not seen in EPR measurements or no experimental evidence is provided for the presence of Ti 3+ ions. ,, Another model suggested that the PL emission peak at 475–500 nm is related to oxygen vacancies, ,,, as observed through EPR analysis, confirming the presence of F + centers, which are ascribed to singly charged oxygen vacancies . First-principles calculations support the experimental results . Recombination of F centers with holes creates an excited state of the emitter, and the transition from the excited state to the ground state gives an emission at 485 nm .…”

Theoretical Calculations Meet Experiment to Explain the Luminescence Properties and the Presence of Defects in m-ZrO2

“…[17][18][19] This proposition is supported by i) EPR analyzes which confirm the existence of F + colour centers (i.e., single charged oxygen vacancies), 16,17 and ii) point defect calculations. 20 Another model suggests the blue emission is induced by on-site d-d transitions of impurity titanium ions Ti 3+ . 12,13 Ti impurities may be naturally present as traces in ZrO 2 and unintentionally substitute zirconium, since zirconium element is commonly extracted from Ti ores (e.g.…”

“…To our knowledge, such simulations have been reported for (only) intrinsic point defects in m-ZrO 2 . 20,[36][37][38][39][40][41][42][43][44] Consequently, this prompted us to revisit in-depth the impact of defects (i.e., native defects and substitution of Zr by Ti) in m-ZrO 2 on its electronic structure.…”