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Preparation of MGF phosphor by O 2 postannealing and impact on luminescence properties and crystal lattice
Author(s) -
Hasegawa Takuya,
Tanaka Ryo,
Ueda Tadaharu,
Toda Kenji
Publication year - 2020
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.17222
Subject(s) - x ray photoelectron spectroscopy , phosphor , photoluminescence , analytical chemistry (journal) , raman spectroscopy , luminescence , crystal structure , materials science , cathodoluminescence , electron microprobe , spectroscopy , crystallography , chemistry , mineralogy , chemical engineering , physics , optoelectronics , optics , chromatography , quantum mechanics , engineering
Mn 4+ ‐activated phosphors, Mg 28 Ge 10 O 48‐δ F δ :Mn 4+ (MGFs), can be obtained through an oxygen postannealing process. Analyses of the crystal structure and elemental composition by powder X‐ray diffraction (XRD) and electron probe microanalysis (EPMA), respectively, indicated that under an O 2 atmosphere, oxygen atoms were substituted with fluorine atoms in the original MGF structure to leach the fluorine atoms with germanium atoms as GeF 4 by oxygen postannealing. The MGF phosphor annealed in O 2 exhibited ~1.3 times higher quantum efficiency (QE) than that annealed in ambient air. The Raman spectroscopy results suggested that an increase in the content of the [Mn 4+ O 6 ] octahedron led to an increase in the QE values. Additionally, the relaxation of lattice defects in the lattice interior and on the surface observed by XRD and X‐ray photoelectron spectroscopy (XPS) measurements could explain the change in thermal quenching behavior between the different atmospheres, and the decrease in lattice defects increased the QE. The investigation of MGF phosphors prepared by different processes provides insight into the relationships among the surface and local structures, chemical composition, and photoluminescence properties. The optimized synthetic procedure increases the Mn 4+ content and decreases the Mn 2+ and Mn 3+ contents in the phosphor, which drastically increases the luminescence efficiency.