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Orange‐Red‐emitting Ca 9 Gd(PO 4 ) 7 :Eu 3+ Phosphors: Judd‐Ofelt Analysis and Investigation on the Thermal Stability, Quantum Efficiency for WLED
Author(s) -
Ha Thu Luu Thi,
Tu Nguyen,
Duc Anh Dao,
Trung Do Quang,
Trung Tran Manh,
Quynh Nhu Tran Thi,
Thi Huyen Nguyen,
Van Quang Nguyen,
Duy Hung Nguyen,
Xuan Viet Dao,
Trung Kien Nguyen Duc,
Thanh Huy Pham
Publication year - 2021
Publication title -
chemistryselect
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 34
ISSN - 2365-6549
DOI - 10.1002/slct.202003891
Subject(s) - phosphor , chromaticity , analytical chemistry (journal) , quantum efficiency , excited state , thermal stability , luminescence , chemistry , light emitting diode , doping , materials science , optics , optoelectronics , atomic physics , physics , organic chemistry , chromatography
Orange‐red‐emitting Eu 3+ ‐doped Ca 9 Gd(PO 4 ) 7 phosphors have been obtained by a sol‐gel technique. These phosphors, excited by UV (270 nm) and near UV light (394 nm), emit orange‐red light in the range of 580–710 nm. The Ca 9 Gd(PO 4 ) 7 :7 mol% Eu 3+ phosphor annealed at 1100 °C shows the highest PL intensity. Judd‐Ofelt analysis reveals that the neighbor surroundings of Eu 3+ ions are asymmetric, and the lowest asymmetry value is found at the dopant ratio of 7 mol%. The optimal phosphor excited by the wavelength of 394 nm displays an excellent thermal stability (∼76.4 % at 160 °C) with an activation energy of 0.163 eV. The corresponding CIE chromaticity coordinates (x; y) and color purity are calculated to be (0.5849; 0.3635) and 84.6 %, respectively. The quantum efficiency values of the Ca 9 Gd(PO 4 ) 7 :Eu 3+ phosphors coated on UV and near‐UV chips are 87.4 % and 5.1 %, respectively. It is the first time that the QE values of Ca 9 Gd(PO 4 ) 7 :Eu 3+ ‐based red and blue‐emitting LEDs are reported.