Optical properties of zinc borate glasses dispersed with Eu-doped SiAlON for white LED applications

Ca-α-SiAlON:Eu²⁺ oxynitride phosphors are typical luminescent materials with high thermal tolerances. A series of zinc borate glass samples (xZnO-(100-x)B₂O₃; mol%) were prepared for investigating their ability to disperse Ca-α-SiAlON:Eu²⁺ phosphor powders. Phosphor in glass (PiG) was prepared with SiAlON and zinc borate glass through a melting process. In the x = 45–60 range, PiGs could be obtained without the degradation of the SiAlON phosphors. The PiG composed of x = 50 glass exhibited the highest quantum efficiency. The glass structures of the mother glasses were investigated by Raman spectra; there was a decrease in the boroxol ring, and pyroborate and orthoborate were formed, on increasing x. From the XRD and SEM images, it was established that ZnAl₂O₄ was formed around the SiAlON powders in PiGs with x = 50, 55, and 60, respectively. This suggests that the partial crystallizations in the PiGs are effective in enhancing the photoluminescence of the SiAlON phosphors.