Synthesis Of High Purity Tetragonal BaTiO₃Powders Via Alkoxide Method

BaTiO3, especially tetragonal BaTiO3, is a traditional functional ceramic material.Owing to its superior piezoelectric, dielectric and ferroelectric properties, it is widelyapplied in the preparation of kinds of electronic ceramics, so called “the pillar ofelectronic ceramics”. With the development of electronic ceramic devices, a higherstandard for the characters such as the powder purity, the particle size, the particlediameter distribution, and the chemical compositions is proposed. Various methods ofpreparation ultrapure and ultrafine tetragonal BaTiO3powders have been absorbed inexperiments by many researchers for improving the properties. Although somesuccesses have been achieved, it is difficult to control the purity and the particle sizeof the powders by most methods, and these problems will directly affect theperformance of barium titanate ceramics. So the preparation of high purity, ultrafineand high tetragonal BaTiO3content of barium titanate powders is particularlyimportant to the development of electronic ceramic industry.In this paper, the synthesis of BaTiO3precursor was based on a alkoxide processused barium hydroxide octahydrate [Ba(OH)2·8H2O] and butyl titanate [Ti(C4H9O)4]as starting materials. Through the study on the conditions of synthesis of BaTiO3powders, we can know that the characteristics of sol and gel were influenced seriouslyby the adding sequences of the ethanol solution with butyl titanate and acetic acidsolution with barium hydroxide octahydrate and pH. And the stable sol was obtainedby the acetic acid solution with barium hydroxide octahydrate adding the ethanolsolution with butyl titanate with adjust pH to5. When the Ba/Ti ratio was1:1, thepowder of tetragonal BaTiO3could be obtained at1000℃for3h.The tetragonal BaTiO3could be obtained at lower temperature by organicamine assist alkoxide method than alkoxide method without organic amine. UsedDEA as surfactant, the content of tetragonal BaTiO3was increased with the extension of time and range up to92%of the powders obtained at1100℃for3h. The contentof tetragonal BaTiO3was increased with increasing calcination temperature, and theparticle size was increased as well. And the dosage of DEA had a significant effect onthe phase composition of the synthesized samples, with the increase of DEA dosage,the content of tetragonal BaTiO3was increased, at the same time, the impurity wasincreased, so the optimal DEA dosage was1mL. When the TEA as surfactant, thehighest content of tetragonal BaTiO3(93%) was obtained by heat treatment of theprecursor at1100℃for3h with1mL DEA dosage. Through the comparison oftetragonal BaTiO3, which obtained with different surfactant, we can know that useTEA as surfactant, the higher content of tetragonal BaTiO3was obtained.