A novel approach on the synthesis of β-SiAlON:Eu²⁺ phosphors from kaolin through carbothermal reduction and nitridation (CRN) route

Abstract

Doping β-SiAlON crystal structure with rare earths leads to a superior tuneable luminescence properties for light emitting diodes (LEDs). However, the widely used conventional methods require high purity starting powders and time consuming processes. Here, a new approach to synthesise Eu²⁺ activated β-SiAlON phosphors from kaolin through carbothermal reduction and nitridation route was introduced. The Rietveld refinement on powder X-ray diffraction method and scanning electron microscopy with energy dispersive X-ray spectroscopy analyses showed that 78·28 wt-%Eu²⁺ doped β-Si_6−zAl_zO_zN_8−z (z = 2·1) was successfully obtained. Photoluminescence examinations under the 267 nm excitation revealed two distinct broad emission peaks: maxima at around 415 nm (violet) and 540 nm (green). Transmission electron microscopy observations demonstrated the incorporation of Eu²⁺ ions into β-SiAlON grains giving the observed violet and green emissions. It is anticipated that this study paves a way for cost effective synthesis of rare earth doped single phase β-SiAlON phosphors in LED applications.

Keywords:

• Ceramic
• Electron microscopy
• Nitrides
• SiAlON
• Luminescence
• Carbothermal reduction and nitridation

Acknowledgement

The authors wish to express their gratitude to Mr N. Ozen for PL measurements.