锂基尖晶石化合物的离子有序、有序畴与微波介电性能研究

Compared with the conventional solid-state sintering route, two-step sintering could restrain the formation of disorder phase in the Li-based spinel ceramics, thereby significantly increasing the dielectric properties of the ceramics. On the basis of previous work, the microstructures of Li-based spinel compound, such as ion ordering and ordered domain, were adjusted by the preparation process and composition. The influence mechanism of preparation process and composition on the ion ordering and ordered domain of the compound was further investigated. The effects of preparation process, composition, and microstructures (such as ionic radius, occupation of ion, ion ordering, order-disorder phase transition, ordered domain and the characteristics of bond) on the microwave dielectric properties of Li-based spinel compound were throughly studied. The adjusting mechanism of microwave dielectric properties of Li-based spinel compound was revealed. Finally, the controllable preparation and performance improvement of Li-based spinel compound were achieved. The completion of this project can further clarify a series of scientific questions, such as the internal influence mechanism of design, preparation, and structure on the performance, which can provide an important theoretical reference for the research of similar materials.

相比于常规固相烧结法，两步烧结法制备工艺能够抑制锂基尖晶石陶瓷的无序相转变，进而显著提高材料的介电性能。本项目在前期工作的基础上，通过制备工艺和组分变化来调节锂基尖晶石化合物的离子有序、有序畴等微结构，深入研究制备工艺和组分对材料离子有序和有序畴的影响机理；系统研究锂基尖晶石化合物制备工艺、组分、微结构（包括离子半径、离子占位、离子有序、有序-无序相变、有序畴及化学键特性等）对该材料微波介电性能的影响规律，揭示锂基尖晶石化合物微波介电性能的调控机理，最终实现该类化合物的可控制备与性能优化。本项目的顺利实施，有助于进一步深入认识材料设计、制备、结构对性能的内在影响机制等一系列科学问题，为其它类似材料的研究提供了重要的理论借鉴。

锂基尖晶石陶瓷具有原料成本低廉，密度低，烧结温度较低及微波介电性能优异等优点，是极具潜力的LTCC候选材料之一。本项目系统研究锂基尖晶石化合物制备工艺、组分、微结构对材料微波介电性能的影响规律，揭示锂基尖晶石化合物微波介电性能的调控机理。项目基本完成了预期目标。项目的主要结论如下：①项目优化了锂基尖晶石陶瓷的两步烧结法工艺，当T1为1150℃，t1为0.5h，T2为950℃，t2为12h时，两步烧结法制备所得的LiZn1/2Ti3/2O4陶瓷相对密度高达98.6%，其Q×f值相比于常规固相烧结而言提高约30%。②项目研究了Li1.33xZn2-2xTi1+0.67xO4陶瓷的相组成、离子有序度和微波介电性能随化学成分的变化规律；随着x的增加，Li1.33xZn2-2xTi1+0.67xO4陶瓷的离子有序度先增加后减小，当x=0.75时离子有序度最高；随着x的增加，陶瓷的介电常数与A1g(1)模拉曼位移成负相关的变化趋势，与分子极化率成正相关的变化趋势；其Q×f值与A1g(1)模半峰宽具有相反的变化趋势，与原子堆积密度无关。③项目研究了(Li1/3Al2/3)2+、(ZnAl)以及(Zn1/3Nb2/3)4+取代对Li2ZnTi3O8陶瓷物相组成、离子有序度和微波介电性能的影响，并探讨了离子有序度和晶格振动对陶瓷微波介电性能的作用机理；随着(Li1/3Al2/3)2+取代量的增加，Li2+xZn1-2xAlxTi3O8陶瓷从有序相转变为无序相，其离子有序度和Q×f值先增加后减小；(ZnAl)取代时，随着取代量的增加，Li2-xZn1-xTi3-xAlxO8陶瓷的离子有序度和介电常数呈现逐渐减小趋势；Q×f值先增加后减小；(Zn1/3Nb2/3)取代时，随着x的增加，陶瓷发生了有序-无序相变，其离子有序度、介电常数和Q×f值均逐渐减小；Li2.1Zn0.8Al0.1Ti3O8陶瓷具有最高离子有序度，且经1100℃烧结时具有优异的微波介电性能：εr = 26.1，Q×f = 96129GHz，τf = -3.2ppm/℃。④通过Li2Zn2Mo3O12和(LiF/CaF2)复合掺杂均能有效降低Li2.1Zn0.8Al0.1Ti3O8陶瓷的烧结温度至900℃左右。