MgO-doped Ba 0.67 Sr 0.33 TiO 3 (BST) ceramics with uniform microstructure and enhanced dielectric loss were prepared by direct coagulation casting via high valence counter ions (DCC-HVCI) method. MgO was utilized as acceptor dopant as well as coagulating agent to release Mg 2+ solidifying ceramic suspensions. Effect of sintering temperature and MgO doping content on microstructure and dielectric properties of BST ceramics was investigated. It was found that the loss tangent value (tan δ) decreased remarkably from 0.025 to 0.004 with increasing MgO concentration from 0.5 to 1.5 mol%. The 1.5 mol% MgO-doped BST ceramics processed high density of 99.5% and tan δ of 0.004 which is improved by 150% compared with that of dry-pressed samples. This improvement can be attributed to the ubiquitous distribution of MgO in BST ceramic matrix leading to the enhanced inhibitive effect. This paper provides a novel facial route to prepare high-performance functional ceramics with high reliability and low cost.
In this paper, in-situ coagulation of 0.9Al 2 O 3 –0.1TiO 2 suspension and microwave dielectric properties of 0.9Al 2 O 3 –0.1TiO 2 ceramics prepared by a novel direct coagulation casting via high valence counter ions (DCC-HVCI) method were proposed. The 0.9Al 2 O 3 –0.1TiO 2 suspension could be coagulated via controlled release of calcium ions from calcium iodate at an elevated temperature. The influence of tri-ammonium citrate (TAC) content, solid loading, and calcium iodate content on the rheological properties of the suspension was investigated. In addition, the influence of coagulation temperature on coagulation time and properties of green bodies was also studied. It was found that the stable 0.9Al 2 O 3 –0.1TiO 2 suspension could be successfully prepared by adding 0.3 wt% TAC and adjusting pH value to 10–12 at room temperature. 0.9Al 2 O 3 –0.1TiO 2 green bodies with uniform microstructures were coagulated by adding 8.0 g/L calcium iodate after treating at 70 °C for 1 h. 0.9Al 2 O 3 –0.1TiO 2 ceramics, sintered at 1500 for 4 h and annealed at 1100°C for 5 h, showed °Cuniform microstructures with density of 3.62±0.02 g/cm 3 . The microwave dielectric properties of 0.9Al 2 O 3 –0.1TiO 2 ceramics prepared by DCC-HVCI method were: ε r = 11.26±0.06, Q × f = 11569±629 GHz, τ
f
= 0.93±0.60 ppm/°C. The DCC-HVCI method is a novel and promising route without binder removal process to prepare complex-shaped microwave dielectric ceramics with uniform microstructures and good microwave dielectric properties.
危险品化学品经营许可证（带存储）