复合氧化物掺杂法制备抗还原BCTZ系陶瓷的研究

提出了一种制备抗还原BCTZ系陶瓷材料的新工艺. 采用溶胶-凝胶法在500～800℃下合成复合氧化物掺杂剂, 此掺杂剂与水热法合成的超细(Ba_1-xCa_x)(Ti_1-yZr_y)O₃粉体混合球磨可得抗还原介质瓷料, 该瓷料可在还原性气氛中烧成适用于贱金属电极的, 具有高介电常数和低介质损耗的多层陶瓷电容器陶瓷材料. 本文讨论了复合氧化物掺杂剂的合成温度、陶瓷烧结温度和退火时间等工艺参数对陶瓷介电性能和微结构的影响. 研究表明, 在低温下合成的纳米颗粒的复合氧化物掺杂剂(纳米掺杂剂)很适合超细瓷料的掺杂改性. 在500～800℃内, 复合氧化物掺杂剂的合成温度升高将导致BCTZ系陶瓷的居里点、介质损耗和介电常数最大值的降低.对陶瓷烧结工艺的研究表明, 采用此新工艺可获得符合Y5V标准的BCTZ系抗还原介质陶瓷, 其室温相对介电常数不小于18000, 介质损耗低于0.7%, 绝缘电阻率达到10¹²Ω·cm, 居里点在5～20℃之间可调, 平均晶粒尺寸G_AV小于4μm. 该新工艺可望用于大容量Y5V镍内电极多层陶瓷电容器的生产.

Preparation of Nonreducible BCTZ Ceramics by Doping Complex Oxide Dopants

A new route was developed for preparation of nonreducible BCTZ ceramics.In this route, complex oxide dopants were obtained by sol-gel process ~via~ heat treatment at 500～ 800℃, and then mixed and milled with (Ba_1-xCa_x)(Ti_1-yZr_y)O₃ powders to get nonreducible BCTZ ceramic powders, which could be fired under reducing atmospheres to get base metal compatible ceramics with high permittivity and low dielectric loss. The influence of synthesizing temperature of the mixed dopants, sintering temperature and annealing time on the microstructure and dielectrical properties of the BCTZ ceramics was studied. The nanosized complex oxide dopants(nanosized dopants) synthesized at low temperature were confirmed to be suitable for the modification of the ultrafine ceramic powders. With the increase of the synthesizing temperature of the complex oxide dopants at 500～800℃, the Curie point, dielectric loss and dielectric maximum K_MAX of the BCTZ ceramics decreased. Studies on the firing process confirmed that nonreducible BCTZ ceramics satisfying the Y5V specification could be prepared via this route. The ceramics had relative dielectric permittivity higher than 18000, dissipation factor below 0.7%, resistivity as high as 10¹²Ω·cm, Curie point in the range of 5～20℃, and the average grain size less than 4μm. This route can be hopeful to be adopted in the production of Y5V Ni-MLCC with large capacitance.