| Popis: |
Low-temperature sintering of high-strength β-eucryptite ceramics with low positive coefficient of thermal expansion (CTE) was attained using Li2O–GeO2 sintering additive. High-purity β-eucryptite could be synthesized using high-purity and fine amorphous silica, α-alumina, and lithium carbonate powder mixture at 950°C via the solid-state reaction route. Accordingly, the mixture was calcined at 900°C, pulverized, compacted, and sintered at 1020°C for 2 h with the sintering additive. The sintering temperature could be lowered by about 300°C, compared with the sintering temperature previously reported. The relative density of the sintered sample reached 99% of true density. Its flexural strength and indentation fracture toughness were 214 MPa and 2.5 MPa·m1/2, respectively. Its CTE (from room temperature to 800°C) was 1.2 × 10–6/K. Its dielectric constant was 5.5 with a loss tangent of 7.5 × 10–3. However, prolonged sintering time resulted in large negative CTE and mechanical weakness in the sintered samples. Microcracks were introduced with prolonged sintering time, which caused their large negative CTE with mechanical weakness. |
