The white LEDs (light-emitting diodes) comprised of a blue LED chip and YAG:Ce³⁺ yellow phosphor are promising new-generation light source which can replace conventional incandescent and fluorescent lamps due to their reliability and low energy consumption. However, these white LEDs are not applicable for indoor lighting purpose due to their less red luminescence and relatively lower color rendering index value. In recent days, rare-earth-doped oxynitride or nitride compounds have been reported to be photoluminescent and may then serve as new phosphors with good thermal and chemical stabilities because  the higher formal charge of N^3- compared with O^2- and the nephelauxetic effect induced by the difference in electro-negativity of nitrogen with oxygen would lead to larger ligand-field splitting of the 5d levels and the center of gravity of the 5d states at lower energy as shown in Fig. 1. In this work, Ca-α-SiAlON:Eu²⁺ based yellow oxynitride micro-crystals were prepared using GPS (gas pressured sintering) method. The crystallinity and particle morphology of the prepared micro-crystals were characterized. The temperature dependence of luminescence properties was investigated from 25 to 275 °C. The Stokes shift and zero-phonon line was calculated mathematically and estimated from the spectral data. The prepared Ca-α-SiAlON: Eu²⁺ showed superior thermal quenching properties compared to a commercially used YAG:Ce³⁺. In addition, the activation energies (ΔE) for thermal quenching of the prepared Ca-α-SiAlON:Eu²⁺ phosphors were determined by Arrhenius fitting.

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1. Luminescence and temperature dependency of β-SiAlON phosphor
2. Synthesis of SiAlON-type Phosphors and Their Photoluminescence Property
3. Preparation and luminescence properties of β-SiAlON:Eu²⁺ green phosphor for high color gamut