Fluorescence properties of Mn4+ in CaAl12O19 compounds as red-emitting phosphor for white LED

Red fluorescence properties of Mn4+ ions in CaAl12O19 compounds prepared by the solid-state reaction were investigated in order to seek a candidate for red-emitting phosphor of white LED. The fluorescence spectrum of CaAl12O19:Mn4+ consists of main peak at 656 nm with three satellite peaks due to the 2E→4A2 transition of Mn4+. The excitation spectrum exhibits a broad band between 250 and 550 nm with three peaks occurring around 338, 398, and 468 nm. The fluorescence intensity excited at 400 nm, which correspond to the wavelength of GaN-based LEDs, is about 80% compared with the excitation spectrum peak at 338 nm. The measured chromaticity of red fluorescence is x=0.728, y=0.269. CaAl12O19:Mn4+ would be suitable for red-emitting phosphor of white LED because CaAl12O19:Mn4+ is excellent in the excitation spectral profile and the chromaticity. The effect of CaF2 and MgF2 additions on the relative fluorescence intensity of CaAl12O19:Mn4+ is discussed in terms of the flux and charge compensation effects.