Seeking the optimal LaTaO{sub 4}:Eu phosphor

Journal Article · Thu Dec 15 00:00:00 EST 2011 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2011.10.008· OSTI ID:21612819

Bleier, Grant C ^[1]; Nyman, May ^[1]; Rohwer, Lauren E.S.; Rodriguez, Mark A ^[1]

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1. Sandia National Laboratories, P.O. Box 5800, Albuquerque, NM 87185 (United States)

Lanthanum orthotantalate, LaTaO{sub 4}, is an excellent host lattice for rare-earth luminescent ions such as Eu{sup 3+} for red emission. However, there are multiple RETaO{sub 4} (RE=rare earth) polymorphs, and the stability of these is controlled predominantly by the RE-radius. Thus it is difficult to obtain a pure phase of LaTaO{sub 4}:Eu as Eu concentration and consequently the RE radius is varied. We recently reported a 'soft-chemical' route that allows crystallization of pure-phase LaTaO{sub 4}:Eu at temperatures as low as 800 Degree-Sign C. In the current report, we investigate polymorph evolution and Eu emission as a function of Eu concentration and annealing temperature. We obtain a maximum quantum yield (QY) of 83% at the highest Eu substitution (25%) for which the low temperature orthorhombic (Pbca) polymorph is stable. Therefore, QY is not limited necessarily by concentration quenching; rather it is limited by polymorph stability as the RE-radius decreases with increasing Eu substitution. - Graphical Abstract: Eu-substituted lanthanum orthotantalates, LaTaO{sub 4}:Eu, are excellent red phosphors. They exhibit up to 83% quantum-yield emission under blue light excitation, optimized through both 'soft chemical processing' and polymorph purity. Highlights: Black-Right-Pointing-Pointer LaTaO{sub 4}:Eu phosphors were synthesized via 'soft-chemical' and solid-state routes. Black-Right-Pointing-Pointer Quantum-yield of Eu emission depends on host polymorph, which changes with La:Eu ratio. Black-Right-Pointing-Pointer Polymorph with optimal Eu-emission is only obtained by 'soft-chemistry'.

• OSTI ID: 21612819
• Journal Information: Journal of Solid State Chemistry, Vol. 184, Issue 12; Other Information: DOI: 10.1016/j.jssc.2011.10.008; PII: S0022-4596(11)00536-6; Copyright (c) 2011 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CRYSTALLIZATION
EUROPIUM
EUROPIUM IONS
IMPURITIES
LANTHANUM
LANTHANUM COMPOUNDS
LUMINESCENCE
ORTHORHOMBIC LATTICES
SOLIDS
TANTALATES
CHARGED PARTICLES
CRYSTAL LATTICES
CRYSTAL STRUCTURE
ELEMENTS
EMISSION
IONS
METALS
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
PHOTON EMISSION
RARE EARTH COMPOUNDS
RARE EARTHS
REFRACTORY METAL COMPOUNDS
TANTALUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS