Thermal stabilities, electronic structures and optical properties of intrinsic defects and dopant Cerium in Ca₄F₂Si₂O₇

Jun WEN, Yau Yuen YEUNG, Lixin NING, Chang-Kui DUAN, Yucheng HUANG, Jie ZHANG, Min YIN

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Abstract

The thermal stabilities, electronic structures and optical properties of intrinsic defects and dopant Ce³⁺ in Ca₄F₂Si₂O₇ host are studied by using density functional theory (DFT) calculations (with PBE and hybrid PBE0 functionals) and wave function-based embedded cluster ab-initio calculations (at the CASSCF/CASPT2/RASSI−SO level). The calculated formation energies reveal that anion vacancies (VO and VF) are always much more energetically favorable than cation vacancies (VCa and VSi) in Ca₄F₂Si₂O₇ host, which is generally prepared under reducing atmospheres. According to the thermodynamic transition energy levels of intrinsic defects readily generated in undoped Ca₄F₂Si₂O₇ (e.g. anion vacancies and antisite defects), we may identify the defect-induced host absorption and emission, whose exact origins are unclear previously. Moreover, on the basis of ab-initio calculated energies and relative oscillator strengths of the 4f→5d transitions of Ce³⁺ at calcium sites with charge-compensating defect OF in their local environments, the excitation bands in the experimental spectra of Ce³⁺ -doped Ca₄F₂Si₂O₇ phosphors are also assigned. The main purpose of this work is to understand luminescence mechanisms of intrinsic defects and extrinsic dopants in the hosts for phosphors by using first-principles approaches. Copyright © 2017 Elsevier B.V. All rights reserved.
Original languageEnglish
Pages (from-to)28-37
JournalJournal of Alloys and Compounds
Volume713
Early online dateApr 2017
DOIs
Publication statusPublished - Aug 2017

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Citation

Wen, J., Yeung, Y.-Y., Ning, L., Duan, C.-K., Huang, Y., Zhang, J., et al. (2017). Thermal stabilities, electronic structures and optical properties of intrinsic defects and dopant Cerium in Ca₄F₂Si₂O₇. Journal of Alloys and Compounds, 713, 28-37.

Keywords

  • Thermal stabilities
  • Intrinsic defects
  • 4f→5d transitions
  • Ce³⁺
  • First-principles
  • Phosphors