Luminescence and afterglow due to defects in β-SiAlON crystal powder

Abstract

Si6−zAlzOzN8−z (β-SiAlON):Eu2+ is among the most suitable green phosphors for white LEDs. To further improve the performance of this phosphor, it is important to investigate the properties of the nitride host crystal, β-SiAlON, which is considered to contain nitrogen vacancy defects (VN) to some extent. From time-resolved fluorescence (TR-F) measurements of β-SiAlON without luminescent activators, we observed blue, yellow, and ultraviolet emissions. We focused on the blue emission typically centered at 460 nm, which was quenched at room temperature, but showed a continued afterglow for several milliseconds. The electron spin resonance signal of Si dangling bonds due to VN in β-SiAlON was observed to have a high concentration of 5.8 × 1016 g−1. We have previously reported the blue emission in nitride phosphor CaAlSiN3:Eu2+, for which the origin has been identified as VN. Therefore, we predicted that the blue afterglow might cause the green emission of the Eu2+ ions to continue for several milliseconds in β-SiAlON:Eu2+. In this study, we proved that spectra decay characteristics measured by TR-F are useful for clarifying the phosphor characteristics interacting with the defects of β-SiAlON, such as VN.