Enhancement of photoluminescence intensity of sintered CaAlSiN3:Eu2+ red phosphor-bismuthate glass composites

Wavelength converters in white light-emitting diodes are usually made by sintering of phosphor-glass powder compacts. An issue is that the sintering process usually results in the reduction of phosphor amount. In the present study, composites containing CaAlSiN3:Eu2+ red phosphor and Bi2O3-B2O3-ZnO-Sb2O5 glass were fabricated by sintering method. Influences of CaAlSiN3:Eu2+ phosphor content (10 vol%-30 vol%) and sintering temperature (410-430 degrees C) on the residual amount of the phosphor phase and the resulting luminescence intensity of the composites were investigated. The change of CaAlSiN3:Eu2+ content due to sintering was analyzed by X-ray diffraction. The interdiffusion between the CaAlSiN3:Eu2+ and glass matrix was examine by scanning electron microscope equipped with energy dispersive X-ray spectrometry. This paper focuses on the change of luminescence intensity after sintering. It was found that although the content of phosphor CaAlSiN3:Eu2+ reduces after sintering; the luminescent intensity of the composites anomalously increases. The optimum luminescence intensity is 14% higher than that of the as-mixed, unfired powder. It is proposed that the incorporation of Bi3+ ions from the glass matrix into the phosphor CaAlSiN3:Eu2+ during sintering improves the luminescence ability of the phosphor particles.