Deep red emission in Eu2+-activated Sr4(PO4)2O phosphors for blue-pumped white LEDs

Komuro, Naoyuki, Mikami, Masayoshi, Saines, Paul J., Akimoto, Katsuhiro, Cheetham, Anthony K. (2015) Deep red emission in Eu2+-activated Sr4(PO4)2O phosphors for blue-pumped white LEDs. Journal of Materials Chemistry C, 3 (28). pp. 7356-7362. ISSN 2050-7534. (doi:10.1039/c5tc01151e) (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided)

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Official URL
http://www.dx.doi.org/10.1039/c5tc01151e

Abstract

he deep red phosphor Sr4(PO4)2O:Eu2+, which has an excitation peak around 450 nm for blue LED applications, is reported. This behavior is unusual for most phosphate phosphors. The crystal structure of Sr4(PO4)2O:Eu2+ is found to be monoclinic P21 and isotypic with Ca4(PO4)2O:Eu2+, which also shows deep red emission. Sr4(PO4)2O:Eu2+ has a larger lattice volume than Ca4(PO4)2O:Eu2+, but their emission and excitation spectra at room temperature are very similar. The key factors are discussed for achieving a large redshift of the 5d levels of Eu2+ ion in order to emit red light. In particular, the importance of the anion polarizability and the distortions of the metal coordination polyhedra are discussed, including the effective coordination number. Importantly, Sr4(PO4)2O:Eu2+ lacks the yellow emission at 77 K, which is found in Ca4(PO4)2O:Eu2+. The differences in thermal quenching behavior for Eu2+ dopants in Sr4(PO4)2O:Eu2+ and Ca4(PO4)2O:Eu2+ are attributed to the degree of auto/photo-ionization due to differences in the band gaps of these compounds. The importance of the large band gap of the host lattice in avoiding non-radiative processes of energy relaxation was confirmed.

Item Type: Article
DOI/Identification number: 10.1039/c5tc01151e
Additional information: Unmapped bibliographic data: LA - English [Field not mapped to EPrints] J2 - J. Mater. Chem. C [Field not mapped to EPrints] AD - Mitsubishi Chemical Corporation, 1060 Naruda, Odawara Kanagawa, Japan [Field not mapped to EPrints] AD - University of Tsukuba, Institute of Applied Physics, 1-1-1 Tennoudai, Tsukuba Ibaraki, Japan [Field not mapped to EPrints] AD - MCHC RandD Synergy Center Inc., 1000 Aoba Kamoshida, Yokohama Kanagawa, Japan [Field not mapped to EPrints] AD - University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, United Kingdom [Field not mapped to EPrints] AD - University of Cambridge, Department of Materials Science and Metallurgy, 27 Charles Babbage Road, Cambridge, United Kingdom [Field not mapped to EPrints] DB - Scopus [Field not mapped to EPrints]
Uncontrolled keywords: Calcium, Crystal structure, Energy gap, Europium, Light emission, Phosphors, Effective coordination numbers, Energy relaxation, Excitation peaks, Excitation spectrum, Metal coordination, Nonradiative process, Phosphate phosphor, Thermal quenching, Europium compounds
Subjects: Q Science > QD Chemistry > QD478 Solid State Chemistry
Divisions: Faculties > Sciences > School of Physical Sciences > Functional Materials Group
Depositing User: Giles Tarver
Date Deposited: 05 Oct 2015 08:46 UTC
Last Modified: 29 May 2019 16:04 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/50711 (The current URI for this page, for reference purposes)
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