Reaction of europium-doped α-SiAlON phosphors with sodium borosilicate glass matrices

The quantum efficiency of composites containing Europium(II)-doped Ca-α-SiAlON phosphors and sodium borosilicate glasses has been reported to decrease with an increase in the Na2O concentration in the glass matrix. To understand the reason for the dependence of this degradation on the glass composition, the reaction between the SiAlON powder and the glass matrix was investigated using a variety of techniques. SEM images of the areas around SiAlON powders showed the formation of a new layer between the SiAlON particles and the glass matrix. EDX images showed that the number of silicon and aluminium atoms decreased while that of boron atoms increased in the new layer. Raman spectra of the composites showed the formation of BN bonds. New layers between the SiAlON phosphor and the glasses were formed owing to exchange between silicon or aluminium and boron; this resulted in the degradation of the composites.