Crystallization resistance behavior of Al2O3-doped calcium bismuth borate glasses

Glass ceramic phosphors provide an effective solution to solve the problems of poor high thermal stability for current commercial WLEDs. The transmittance of sealing glass is one of the key factors to achieve high luminous performance of glass ceramic phosphors. In this work, a relative high transmittance and superior crystallization resistance frit seal of Al2O3-doped calcium bismuth borate glasses were successfully prepared. The crystallization resistance behaviors related to structures, morphologies were investigated. As increasing Al2O3 concentrations from 0 to 6 mol%, the glass structure becomes more compact. The capability of crystallization resistance and transmittance for the second sintering samples increase with increasing Al2O3 contents. 6 mol% Al2O3-doped glass exhibits virtually amorphous state and the transmittance is close to 70%. The glass transition activation energy (Eg) and crystallization activation energy (Ep) of glass sample with low Al2O3 content are about 382 kJ/mol and 280 kJ/mol and the precipitation of crystal phase possibly is Bi4B2O9. The YAG:Ce3+ glass ceramic prepared with 6 mol% Al2O3-doped glass yields a LE of 123.2 lm/W, a CCT of 5856 K and a CRI of 67.6. The as-prepared calcium bismuth borate glass with 6 mol% Al2O3 is a promising package material in the field of high-power WLEDs.