Due to the weak thermal and chemical stability of organic resins which are used for conventional white LEDs to embed phosphors, inorganic color converters such as phosphor ceramics and phosphor-in-glasses are currently being used to replace conventional color converters based on organic materials, especially for high power and high brightness applications. In this paper we report on the study of sintered glass ceramics based on low melting glass in which commercial YAG:Ce3+ phosphors are embedded. A low Tg is necessary to avoid high temperature sintering which can damage the optical properties of the embedded phosphors. Two different types of glass have been studied: borosilicate and tellurite. The compositions have been optimized in terms of stability, sintering efficiency and thermal conductivity. Selected samples were optical charterized using a GaN high power multimode 450 nm Laser Diode, with a maximum output power of 1.6 W at 1.5 A.
We investigated both the effect of high irradiation density and high operating temperature, as well as their color-rendering index. The sintered glass ceramic based on borosilicate glass showed better high power stability because of its higher thermal conductivity.
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