提高致密细晶微波复合陶瓷(Ba_(0.75)Sr_(0.25))TiO_3-MgO烧结性能的研究

Study on the Enhanced Sinterability of Dense and Fine-grained (Ba_(0.75)Sr_(0.25))TiO_3-MgO Microwave Composite Ceramics

采用改进的机械化学作用与混杂工艺相结合的制备方法，在1200℃制备出结晶完全、致密的细晶（Ba0．75Sr0.25）Ti03－MgO（BST-MgO）复合陶瓷材料，其烧结温度比传统的固相反应低150－300℃。样品的介电性能研究发现，介电温谱在一50℃左右，介电常数呈明显的弥散现象，这是由于复合块体材料细晶的微观结构与非铁电相MgO共同作用的结果。样品的居里点在5℃左右，在居里点介电常数呈现介电弛豫现象。在室温、100kHz时，介电常数和介电损耗分别约为1300和0．005；在偏置电场为1．0kV／mm时，介电可调性为S％o。

A well-developed, dense and fine-grained （Ba0. 75 Sr0. 25 ） TiOa-MgO （denoted as BST-MgO） ceramic composite was fabricated at low sintering temperature of 1200 ℃ using a modified hybrid processing based on the mechanochemical technique. The fabrication temperature was 150--300 ℃ lower than that required by using conventional solid-state process. Temperature dependent didectric constant and loss tangent of the BST-MgO composite exhibited two phase transitions. The first one was at about --50 ℃, showing a broad and diffused phase transition; while the second one was at about 5 ℃ （the expected Curie temperature）, indicating a relaxation phenomenon. At 100 kHz and room temperature, the measured dielectric constant and low loss tangent were about 1300 and 0. 005, respectively. Finally, the measured dielectric room-temperature tunability at 100 kHz and 1 kV/mm were found to be 5 %.