Exploration of zinc phosphate glasses dispersed with Eu-doped SiAlON for white LED applications

Abstract

Ca-α-SiAlON:Eu2+ oxynitride phosphors are typical luminescent materials and have been used to produce white light when embedded in the resin surrounding blue LEDs. However, this arrangement has a short lifetime due to thermal degradation, and an alternative matrix to disperse phosphors is required. A series of zinc phosphate glasses (xZnO-(100−x)P2O5 where x=50, 55, 60 and 65), were prepared to investigate their ability to disperse Ca-α-SiAlON:Eu2+ phosphor powders. The glass formation of the glass–phosphor composites depended on both the glass transition temperature, Tg, of the mother glass, and the glass structures (as investigated by NMR and Raman spectra). Due to a lower Tg, the glass–phosphor composites were obtained more easily when x=60mol%; however, this was limited to <4 mass% SiAlON due to an increase of short chains in the glass network. The color generated by irradiation by a blue LED (of wavelength 450nm), depended on the glass composition, concentration of SiAlON, and the thickness of the composite. Considering the glass formation and quantum efficiency, the x=60mol% glass and 3mass% SiAlON composite was the most suitable for use as a host material for white LEDs.