CuO-TiO_2复合助剂低温烧结氧化铝陶瓷的机理(Ⅱ)

固定CuO(0.4%)和TiO₂(4%)的添加量、改变TiO₂(0--32%)和CuO(0--3.2%)的添加量(质量分数, 下同), 研究了CuO--TiO₂复合助剂对氧化铝陶瓷烧结性能、微观结构、物相组成以及烧结激活能的影响, 以揭示复合助剂的低温烧结机理。结果表明, 在1150--1200℃TiO₂固溶入Al₂O₃生成Al₂Ti₇O₁₅相, 并生成大量正离子空位提高了扩散系数, 从而以固相反应烧结的作用机理促进了氧化铝陶瓷的致密化; TiO₂在Al₂O₃中的极限固溶度为2%--4%, 超过固溶极限的TiO₂对陶瓷烧结没有促进作用; 添加适量的CuO(0.4%)可将TiO₂在Al₂O₃中的固溶温度降低到1100℃以下, 并以液相润湿作用促进氧化铝陶瓷的致密烧结。陶瓷烧结激活能的计算结果定量地印证了上述烧结机理; 当在Al₂O₃中添加4%的TiO₂和2.4%的CuO, 可将烧结激活能降低到54.15 kJ ? mol-1。

Mechanism of Lowering the Sintering Temperature of Al2O3 Ceramic by the Addition of CuO–TiO2 (II)

The effects of CuO and TiO₂ additives on the sintering behavior, microstructure, phase composition, sintering activation energy and the mechanism of lowering the sintering temperature of Al₂O₃ ceramics have been investigated. The TiO₂ began to dissolve into Al₂O₃ and formed Al₂Ti₇O₁₅ solid solution at the sintering temperature of 1150–1200^oC  , and the diffusion coefficient improved largely with the augment of Al ³⁺ vacancy concentration, which was the essential reason why the sintering process of A1₂O₃ ceramic had been promoted by the TiO₂ addition. However, the solid solubility limit of TiO₂ was 2%–4% (mass fraction), and it was unuseful for lowering the sintering temperature of A1₂O₃ ceramic by doping superfluous TiO₂. The temperature of TiO₂ dissolved into Al₂O₃ could be lowed down to 1100   with the addition of 0.4% CuO, which was effective to promote the sintering process of A1₂O₃ ceramic. The sintering activation energy of alumina ceramic doped with different CuO–TiO₂ was consistent with the above results. The sintering activation energy of A1₂O₃ ceramic was reduced to 54.15 kJ·mol⁻¹ by adding 4% TiO₂ and 2.4% CuO.