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Phase Transformation in Ca 3 (PO 4 ) 2 :Eu 2+ via the Controlled Quenching and Increased Eu 2+ Content: Identification of New Cyan‐Emitting α‐Ca 3 (PO 4 ) 2 :Eu 2+ Phosphor
Author(s) -
Ji Haipeng,
Huang Zhaohui,
Xia Zhiguo,
Molokeev Maxim S.,
Chen Mingyue,
Atuchin Victor V.,
Fang Minghao,
Liu Yan'gai,
Wu Xiaowen
Publication year - 2015
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.13787
Subject(s) - phosphor , cyan , monoclinic crystal system , analytical chemistry (journal) , luminescence , rietveld refinement , materials science , crystal structure , tantalate , doping , quenching (fluorescence) , mineralogy , crystallography , chemistry , fluorescence , ferroelectricity , optoelectronics , optics , physics , chromatography , dielectric
A case of phosphor is reported where the cooling rate parameter significantly influences the luminescence property. By quenching the sample after the high‐temperature solid‐state reaction at 1250°C, we successfully prepared the Eu 2+ ‐doped α form Ca 3 ( PO 4 ) 2 (α‐ TCP :Eu 2+ ) as a new kind of bright cyan‐emitting phosphor. The unusual emission color variation (from cyan to blue) depends on the cooling rate after sintering and Eu 2+ doping level as it was observed in the TCP ‐based phosphors. By the Rietveld analysis, it is revealed that the cyan‐ and blue‐emitting phosphors are two different TCP forms crystallizing in the monoclinic (space group P 2 1 / a , α‐ TCP ) and the rhombohedral structure (space group R 3 c , β‐ TCP ), respectively. Upon 365 nm UV light excitation, α‐ TCP :Eu 2+ exhibits an asymmetric broad‐band cyan emission peaking at 480 nm, while β‐ TCP :Eu 2+ displays a relatively narrow‐band blue emission peaking at 416 nm. The Eu 2+ ‐doping in Ca 3 ( PO 4 ) 2 shifts the upper temperature limit of the stable structural range of β form from 1125°C to ≥1250°C. Moreover, the crystal structures of α/β‐ TCP :Eu 2+ were compared in the aspects of compactness and cation site sets. The emission thermal stability of α/β‐ TCP :Eu 2+ was comparatively characterized and the difference was related to the specific host structural features.