The origin of bimodal luminescence of β-SiAlON:Eu2+ phosphors as revealed by fluorescence microscopy and cathodoluminescence analysis

Eu 2+ -doped SiAlON phosphors with the composition of Eu x Si 6− z Al z O z N 8− z (0.5   ≤   z   ≤   3) at a fixed x   =   0.01 were synthesized by the gas pressure sintering method. Dependence of luminescence properties on the phase compositions in β-SiAlON:Eu 2+ phosphors has been examined via fluorescence microscope and scanning electron microscope equipped with a cathodoluminescence spectrometer and an energy dispersive spectrometer. Bimodal emission (green and violet) from β-SiAlON phase is observed in the samples with z   ≥   2, indicating co-existence of two different kinds of coordination for Eu 2+ ions in the host lattice.