Low temperature sintering of .BETA.-spodumene ceramics with low thermal expansion using Li2O-Bi2O3 as a sintering additive

Abstract

Low temperature sintering of β-spodumene ceramics with low coefficient of thermal expansion (CTE) was attained using Li2O–Bi2O3 sintering additive. High purity β-spodumene could be synthesized at 1150°C using high purity and fine amorphous silica, γ-alumina and lithium carbonate powder mixture via the solid state reaction route. The mixture was calcined at 800°C, pulverized, compacted, and sintered with or without the sintering additive at 800–1350°C for 2 h. The relative density reached 95% for the sample sintered with 3 mass % of Li2O–Bi2O3 additive at 1050°C for 2 h. As a result, sintering temperature could be lowered about 200°C by adding the sintering additive, compared with the sintering temperature previously reported. The flexural strength of the sample sintered with 3% of Li2O–Bi2O3 additive at 1050°C for 2 h was 118 MPa. Its CTE (from R.T. to 800°C) was 0.2 × 10−6/K. Its dielectric constant was 8.2 with loss tangent of 1.4%.