以Li2O-SiO2（LSO）复合组分作为助烧剂,比较纳米掺杂和直接掺杂对X7R型BaTiO3基陶瓷显微结构和介电性能的影响,并进一步研究直接掺杂LSO的用量及烧结温度的影响,同时通过缺陷化学理论探讨了陶瓷的烧结机制。实验结果表明与纳米掺杂相比,直接掺杂助烧剂能够使掺杂元素进入晶格产生离子空位等缺陷,减少了物质迁移所需的活化能,从而有效促进陶瓷致密化过程,显著改善陶瓷的微观形貌及其介电性能。陶瓷样品的介电常数随着LSO助烧剂掺杂量的增加先增大后减小;当助烧剂掺杂量为0.08%（摩尔分数）时,样品可在1200℃烧结,室温介电常数达到4855,且容温特性满足X7R标准。通过直接掺杂能够使助烧剂十分均匀地分布在陶瓷材料中,可以显著减少助烧剂的用量,达到明显降低烧结温度的目的,并起到助烧兼改性的作用。
In this study,X7R type BaTiO3-based ceramics were prepared by the nano-doping process and directly doping method respectively by using Li2O-SiO2（LSO） nano-composites as sintering aids.The effect of nano-doping and directly doping of Li2O-SiO2 sintering aids on the microstructure and dielectric properties of the ceramics were studied.And we studied the effect of LSO amounts and sintering temperature on the microstructure and dielectric properties of the ceramics.The sintering mechanism was also discussed by defect chemistry theory.The results indicate that,the doping elements enter the crystal lattice by directly doping method and produce ion vacancies.This can decrease the diffusion activation energy and then leads to an effective densification as well as significant microstructure improvement,when compared with the performance obtained on the nano-doping process.Dielectric constant of the specmens were enhanced with an increase of LSO up to 0.08mol% and then decreased.The specimens with 0.08mol% LSO sintered at 1200℃ for 4h showed εr of 4855 and met X7R character.The sintering aids can be uniformly distributed in the ceramics by directly doping method and the amounts of sintering aids can be decreased apparently.Finally,the sintering temperature of ceramics has been lowered significantly and the properties of ceramics have been improved obviously.
参考文献
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