The thermal properties of cordierite/diopside composites fabricated by glass-ceramics process for LED packages

Cordierite/diopside composites were manufactured by the heat-treatment of green compacts composed of diopside (CaO-MgO-2SiO(2)) and cordierite (2MgO-2Al(2)O(3)-5SiO(2)) glass frits. The thermal properties were analyzed as a function of the type and intensity of the crystalline phases generated and the microstructure. The composites contained 0-30 wt% diopside glass frits had alpha-cordierite as the major phase and the mu-cordierite as the minor phase (designated as alpha-series). In the composites containing 40-80 wt% of diopside frit, the mu-cordierite and diopside crystals were generated as the major and minor phase, respectively (designated as mu-series). Adding diopside glass frit decreased the thermal conductivity of the alpha-series specimens but increased that of the mu-series specimens. The density of the composites showed a linearly proportional relationship with the thermal conductivity. At an equal density, the alpha-series specimens had higher thermal conductivity than the hi-series specimens. 30-50 nm crystals were sparsely observed in the microstructures of the g-series specimens and 30-100 nm crystals were formed compactly in the alpha-series specimens. The cordierite/diopside composites manufactured in this research can be applied as LED packaging materials due to their adequate thermal conductivity of 1-3 W/mK and their diffusivity of 0.5-1.3 mm(2)/s. (C) 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved.