Exploration of zinc phosphate glasses for white LED applications

Ca-alpha-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-alpha-SiAlON:Eu2+ phosphor powders. The glass formation of the glass-phosphor composites depended on both the glass transition temperature, T-g, of the mother glass, and the glass structures (as investigated by NMR and Raman spectra). Due to a lower T-g, the glass-phosphor composites were obtained more easily when x = 60 mol%; however, this was limited to <4 mass% SiAION due to an increase of short chains in the glass network. The color generated by irradiation by a blue LED (of wavelength 450 nm), depended on the glass composition, concentration of SiAlON, and the thickness of the composite. Considering the glass formation and quantum efficiency, the x = 60 mol% glass and 3 mass% SiAlON composite was the most suitable for use as a host material for white LEDs. (C) 2013 Elsevier B.V. All rights reserved.