Performance of Ce:YAG-MgO composite ceramics as high-power LED phosphor densified by non-reactive sintering

Abstract

A novel white light converter has been successfully synthesized using a non-reactive sintering process to afford a fully densified Ce:YAG-MgO composite ceramic phosphor with high wavelength conversion efficiency under excitation at 450 nm. The composite obtained by HIP (hot isostatic pressing) treatment at 1080 ºC has no residual pores and the XRD (X-ray diffraction) analysis shows that there are no secondary phases other than Ce:YAG and MgO, moreover, the EDS (Energy-dispersive X-ray spectroscopy) analysis indicates no interdiffusion at the Ce:YAG-MgO contact interface. The thermal conductivity of 5–7.5 wt% Ce:YAG-added MgO composites is over 40 W/mK, nearly reaching the theoretical value. Due to the synergetic effect of “the difference in refractive index between MgO and Ce:YAG” and “MgO matrix with strong birefringence”, the excitation light (450 nm) is multiply scattered inside the composite medium, which provides efficient excitation even in a thin medium, resulting in the photoluminescence intensity that is 2.6 times higher than that of transparent Ce:YAG ceramics. This innovative white light converter combines a highly thermal conductive MgO matrix and Ce:YAG phosphor with high emission intensity.