宽温度稳定Ba0.80Sr0.20TiO3/Pb0.82La0.12TiO3复合厚膜的低温制备研究

利用溶胶-凝胶法合成了两种不同居里温度的Ba_0.80Sr_0.20TiO₃(BST-80)和Pb_0.82La_0.12TiO₃(PLT-12)铁电陶瓷微粉.以陶瓷微粉,低熔点玻璃粉末PbO-B₂O₃等混合配制浆料,应用丝网印刷法在ITO石英玻璃基板上制备厚膜,并在550-750℃温度下于密封的石英套管中烧结致密化,成功的在750℃低温下制备出BST-80和PLT-82晶相稳定共存的复合厚膜.厚膜的相关性能通过X射线衍射仪(XRD)、扫描电子显微镜(SEM)、阻抗仪(LCR)等手段进行测试.结果表明,厚膜的形成主要通过750℃下PbO-B₂O₂玻璃相的浸润及均匀包裹到颗粒表面并经颗粒在玻璃相中一定的液相传质过程而致密化;通过控制玻璃相的包裹及控制颗粒的扩散实现颗粒相的稳定共存.厚膜中PLT-82晶相的晶格受Pb²⁺离子扩散进入玻璃相而略有缩小.这种复合厚膜的介电常数在较宽的温度范围0-300℃间的变化率<18％,具有较高的温度稳定性.

Low Temperature Preparation of the Temperature-stable Ba0.80Sr0.20TiO3/Pb0.82La0.12TiO3 Composite Thick Films

Sol-gel derived Ba_0.80Sr_0.20TiO₃ and Pb_0.82La_0.12TiO₃ ferroelectric powders and a low-melting PbO-B₂O₃ glass powder were mixed to prepare paste. The composite thick films were successfully prepared by screen printing onto the quartz glass substrates with the ITO bottom electrode and then calcined in the sealed silica tube at the low temperature between 550℃ and 750℃. XRD, SEM and LCR were used to measure the structure and dielectric constants of the composite thick films. The results show that the high infiltration of the PbO-B₂O₃ liquid phase in the thick film gives rise to the ferroelectric powders uniform encapsulated by the PbO-B₂O₃ phase at the temperature of 750℃ and then the mass transport through the liquid phase, which promote the densification of the thick film. The stable coexistence between the Ba_0.80Sr_0.20TiO₃ and Pb_0.82La_0.12TiO₃ crystal phases can be controlled directly by both the glass phase encapsulated and the diffusion from the particles to the glass phase. The slight reduction of the lattice of the PLT-82 crystal phase in the thick film occurs due to Pb²⁺ ion vacancy generated by the diffusion. The relative dielectric constant of the composite thick films exhibits the temperature-stable behavior. The variance of the dielectric constants is less than 18% in the temperature range 0--300℃