Papers by Keyword: Low Sintering

Abstract: The low temperature sintering alumina crucible were prepared with four different formulas by modified the original formula with sintering aids CaCO₃, MgCO₃, Ball clay and ZrO₂. The admixtures were mixed and grinded by ball mill for 24 hrs. The slurry alumina was casted in plaster mold for test samples and crucibles. After dried, the alumina was sintered at 1450, 1500 and 1550°C for 2 hrs. The sintering crucible was investigated chemical composition and properties. The crucibles were tested by melting glass at 1500°C. As a result, the composition (% by weight) was 85-94% Al₂O₃ 2-3% SiO₂ 1.7-6.5% ZrO₂ 1.4-3.5% CaO and 0.3-1% MgO with the phase of aluminum oxide (Al₂O₃), spinel (MgAl₂O₄) and baddeleyite (ZrO₂). The alumina crucible sintered at 1550°C have 9-12 % firing shrinkage density 3.35-3.64 g/cm³ and the coefficient of thermal expansion at 7.72-8.17 ´ 10^-6 K^-1 which depended on the composition that was similar to commercial 94% alumina (sintered at 1700°C). After tested for the melting glass, these crucibles had high thermal shock resistance which could move out of furnace without any cracks. The selected formula could be used for crucible production with lower sintering temperature, even it decreased sintering temperature from 1700°C to 1550°C. This would save 15-20% of the energy consumption.

Abstract: The optimized composition and sintering process of the low sintering X7R-type temperature-stable dielectric ceramics based on Barium Titanate in reducing atmosphere have been investigated. Flux aids SiO2-B2O3-Li2O were used in the experiments. The influence of composition and the content of flux agent on the microstructures and properties of ceramics materials were systemically studied. The X7R-type dielectric ceramics materials could be sintered at low temperature of 950oC in H2/N2 atmosphere, by optimizing flux content and adjusting process parameters. The dielectric constant of ceramics was effectively improved using two-step sintering process.