The crystallization behavior and thermal properties of diopside-based glass ceramics fabricated from a CaO–MgO–SiO2-(Li2O) glass system were studied as functions of the CaO/MgO ratio. Crystalline diopside was identified as the main phase in all specimens with CaO/MgO ratios of 0.4 ~ 2.3. Small amounts of β-wollastonite and forsterite were generated in specimens of higher and lower ratios of CaO/MgO compared to the specimen of CaO/MgO = 1, respectively. The thermal conductivity increased with increasing major peak intensity of diopside. The thermal conductivities of the glass ceramics of CaO/MgO = 2.3 and 0.4 were 34% and 14% lower, respectively, in comparison with the value for the CaO/MgO = 1. The chemical resistance of the glass-ceramics to HF acid solution increased with decreasing CaO/MgO ratio due to the formation of forsterite phase. The diopside-based glass-ceramics of CaO/MgO ratio = 0.7 sintered at 823oC/2 hrs in the CaO-MgO-SiO2-(Li2O) system had a thermal conductivity of 3.3W/mK, as high as in pure diopside, and much higher chemical durability than the pure diopside glass-ceramics. Thus, the diopside-based glass-ceramics containing a small amount of forsterite showed high feasibility for application to LED packaging materials through LTCC processing.

Keywords: Thermal properties, Glass ceramics, Dopside, Forsterite, Chemical durability, CaO/MgO ratio.