Diopside is a ceramic material with excellent physical and chemical properties. However, when it is applied as an LED packaging material, heat dissipation of the LED element is not sufficient due to its relatively lower thermal conductivity, which may cause degradation of the LED function. In this study, glass-ceramics based on a ZrO2-CaO-MgO-SiO2 system, in which diopside is the main crystal phase, were prepared by heat-treating the glass, which was composed of zircon (ZrO2-SiO2) powders and diopside (CaO-MgO-2SiO2) powders. The possibility of using the glass-ceramics as a packaging material for LEDs was then investigated by analyzing the density, shrinkage, thermal conductivity, and phases generated according to the amount of zircon powder added. The density and shrinkage of specimens decreased slightly and then increased again with the amount of ZrO2-SiO2 added within a range of 0~0.38 mol. Even though the crystal phase of zircon does not appear in the ZrO2-CaO-MgO-SiO2 system, the glass containing 0.38 mol zircon powder showed the highest thermal conductivity, 1.85 W/ mK, among the specimens fabricated in this study: this value was about 23% higher than that of pure diopside. It was found that the thermal conductivity of the glass-ceramics based on a ZrO2-CaO-MgO-SiO2 system was closely related to the density, but not to the phase type. Zirconia (ZrO2), a component oxide of zircon, plays an important role in increasing the density of the specimen. Furthermore the thermal conductivity of glass-ceramics based on a ZrO2-CaO-MgO-SiO2 system showed a nearly linear relationship with thermal diffusivity.

Keywords: Glass-ceramics, Zircon, LED Packaging, Diopside, Thermal conductivity.