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以硝酸钡、硝酸锶、钛酸丁酯和柠檬酸为原料,采用自燃烧法合成了晶粒尺寸～20nm Ba0.5Sr0.5TiO3(BST)超细粉体。利用溶液中各种离子分布与溶液pH值的关系,研究了金属离子-柠檬酸水溶液体系中的络合pH条件,得到了自燃烧制备BST的最佳pH值范围。借助TG-DSC、IR、XRD和TEM研究了硝酸盐-柠檬酸盐干凝胶的自蔓延燃烧机理以及产物的物相结构和形貌特征。结果表明,自燃烧蔓延是在硝酸根离子和羧酸根离子之间进行的热诱导阴离子氧化还原反应,其中,硝酸根离子作氧化剂,羧酸根离子作还原剂。燃烧后得到了分散均匀,团聚少的BST纳米晶。将粉末压片在1100～1250℃烧结2h后,测试了烧结体样品的电容和介电损耗随频率变化的关系,并对变化的原因进行了详细分析。
The grain size ~ 20nm Ba0.5Sr0.5TiO3 (BST) ultrafine powder was synthesized by self-combustion method using barium nitrate, strontium nitrate, butyl titanate and citric acid as raw materials. Based on the relationship between the various ions in the solution and the pH value of the solution, the conditions of complexation of pH in the metal ion-citric acid aqueous solution were studied. The optimal pH range of self-combustion BST was obtained. The self-propagating combustion mechanism of nitrate-citrate xerogel and the phase structure and morphology of the product were studied by means of TG-DSC, IR, XRD and TEM. The results show that the self-burning spread is a heat-induced anion redox reaction between nitrate ion and carboxylate ion, in which nitrate ion is used as oxidant and carboxylate ion is used as reducing agent. BST nanocrystals with uniform dispersion and less agglomeration were obtained after combustion. After sintered at 1100-1250 ℃ for 2h, the relationship between the capacitance and dielectric loss of the sintered samples with frequency was tested. The reason of the changes was analyzed in detail.