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Ce3+-Activated γ-Ca2SiO4 and Other Olivine-Type ABXO4 Phosphors for Solid-State Lighting

DOI: 10.1021/cm501516m DOI Help

Authors: Ali Kalaji (University of Cambridge) , Masayoshi Mikami (Mitsubishi Chemical Group Science and Technology Research Center, Inc) , Anthony K. Cheetham (Department of Materials Science and Metallurgy, University of Cambridge)
Co-authored by industrial partner: Yes

Type: Journal Paper
Journal: Chemistry Of Materials , VOL 26 (13) , PAGES 3966 - 3975

State: Published (Approved)
Published: July 2014
Diamond Proposal Number(s): 7854

Abstract: Yellow-emitting phosphors activated by Ce3+ are key components of white light-emitting diodes (LEDs) based on the blue (Ga,In)N LED. In these phosphors, the electronic environment around Ce3+ determines its photoluminescence wavelengths. Placing Ce3+ in octahedral sites in oxides can potentially lead to yellow or orange phosphors that can compete with the important commercial phosphor, Y3Al5O12:Ce. However, there are very few examples of such materials. In this article, we explore the photoluminescent behavior of Ce3+ in oxides with the olivine structure, whereby two distorted octahedral doping sites exist. We demonstrate that the promising new yellow phosphor γ-Ca2SiO4:Ce requires a second dopant, Al3+, to avoid the formation of the undesired β polymorph. Our results indicate that the yellow emission is indirectly caused by the complex polymorphism of Ca2SiO4, particularly the low temperature formation of the γ-phase. The dramatic shift in emission from yellow to light-blue when this phosphor is heated to 800 °C is explained in terms of the redistribution of Ce3+ in the lattice. A similar effect is observed when Si4+ is substituted by Ge4+. The light-blue emission of Ca2GeO4:Ce,Al is reported as well as the photoluminescent properties of the Ca2(Ge,Si)O4:Ce,Al solid solution.

Subject Areas: Chemistry, Materials

Instruments: I11-High Resolution Powder Diffraction

Added On: 30/10/2014 14:21

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