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

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.

Encaged-anion tunable luminescence of Ce3+-activated single host Ca12Al14O32Cl2 phosphor for UV pumped multi-color LEDs

“…Phosphor converted light-emitting diode (LED) is attracting significant attention as one of the most promising general illumination sources in recent years because of its advantages, such as low energy consumption, high efficiency, and long lifetime [1][2][3][4][5][6][7][8]. Common approaches to produce white light emitting diodes (WLEDs) include blending three primary colored phosphors with different hosts upon UV LED excitation or a combination of a blue LED emission with a single-host yellow phosphor [9][10][11][12][13].…”

Site occupancy of Ce3+ in β-Ca2SiO4: A combined experimental and ab initio study

“…Recently, great interest has been shown in the Ce-doped alkaline earth orthosilicate, Ca 2 SiO 4 , for its potential applications as phosphors in white light emitting diodes (LEDs) [8][9][10]. At room temperature, the undoped Ca 2 SiO 4 stabilizes in the c-phase, having an orthorhombic olivine structure with the space group Pbnm (No.…”

“…62) [11]. When doped with Ce 3+ , the compound exhibits intense yellow emission upon excitation by blue light [8,9]. There is also a metastable b-phase of Ca 2 SiO 4 at room temperature, which crystallizes in monoclinic symmetry with the space group P2 1 /n (No.…”

The effect of doping La3+ on structure and luminescent properties of Sr2SiO4:Eu2+ phosphors

“…To improve the performance of silicate phosphors, many researchers pay their attention to the field of M 2 SiO 4 -based phosphors. Ali et al [16] have synthesized a novel yellow emitting γ-Ca 2 SiO 4 :Ce phosphor. Denault et al [17] have studied the luminescence properties of BaSiO 4 :Eu 2 þ Orthosilicate Phosphors via doping Sr 2 þ .…”