Unraveling the Energy Levels of Eu2+ Ions in MBe20N14:Eu2+ (M = Sr, Ba) Phosphors

Amin, M. Ruhul; Elzer, Eugenia; Schnick, Wolfgang und Moewes, Alexander (2021): Unraveling the Energy Levels of Eu2+ Ions in MBe20N14:Eu2+ (M = Sr, Ba) Phosphors. In: Journal of Physical Chemistry C, Bd. 125, Nr. 22: S. 11828-11837

Abstract

Band gaps, electronic structures, optical properties, and energy levels of the incorporated activator Eu2+ ions of the recently synthesized luminescent nitridoberyllates, MBe20N14 :Eu2+ (M = Sr, Ba), are studied with a combination of soft X-ray spectroscopy and density functional theory (DFT) calculations. X-ray absorption and X-ray emission spectroscopy at the N K-edge are used to determine the band gap, which is found to be 4.4 +/- 0.3 eV for both compounds. The measured value agrees well with the DFT-calculated band gaps of 4.6 eV for M = Sr and 4.4 eV for M = Ba, employing the modified Becke-Johnson exchange potential. The 4f(6)5d(1) energy level of the Eu2+ ions is determined directly from the separation between the bottom of the conduction band and the lowest 4f(6)5d(1) states of Eu2+ ions and is found to be 0.31 +/- 0.04 eV for M = Sr and 0.30 +/- 0.04 eV for M = Ba from resonant inelastic X-ray scattering measurements. X-ray excited optical luminescence (XEOL) measurements show luminescence in the blue spectral region at 430 nm for M = Sr and 427 nm for M = Ba, which are due to the 4f(6)5d(1) -> 4f(7) transition. Therefore, XEOL enables the determination of the 4c energy levels and thus provides a deep understanding of the energy levels and radiative processes involved in MBe20N14 :Eu2+ (M = Sr, Ba).

• Dokumententyp: Zeitschriftenartikel
• Fakultät: Chemie und Pharmazie > Department Chemie
• Themengebiete: 500 Naturwissenschaften und Mathematik > 540 Chemie
• ISSN: 1932-7447
• Sprache: Englisch