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Low-Temperature Sintering of β-Spodumene Ceramics Using Li2OGeO2 as a Sintering Additive


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Low-temperature sintering of β-spodumene ceramics with low coefficient of thermal expansion (CTE) was attained using Li2OGeO2 sintering additive. Single-phase β-spodumene ceramics could be synthesized by heat treatment at 1000°C using highly pure and fine amorphous silica, α-alumina, and lithium carbonate powders mixture via the solid-state reaction route. The mixture was calcined at 950°C, finely pulverized, compacted, and finally sintered with or without the sintering additive at 800°C–1400°C for 2 h. The relative density reached 98% for the sample sintered with 3 mass% Li2OGeO2 additive at 1000°C. Its Young's modulus was 167 GPa and flexural strength was 115 MPa. Its CTE (from R.T. to 800°C) was 0.7 × 10−6 K−1 and dielectric constant was 6.8 with loss tangent of 0.9% at 5 MHz. These properties were excellent or comparative compared with those previously reported for the samples sintered at around 1300°C–1400°C via melt-quenching routes. As a result, β-spodumene ceramics with single phase and sufficient properties were obtained at about 300°C lower sintering temperature by adding Li2OGeO2 sintering additive via the conventional solid-state reaction route. These results suggest that β-spodumene ceramics sintered with Li2OGeO2 sintering additive has a potential use as LTCC for multichip modules.