核壳结构LaMxMn1-xO3@BaTiO3-Bi(Me)O3复合热敏陶瓷构筑及深低温电荷输运机制研究

It is difficult to obtain thermistor ceramics with wide temperature range under deep cryogenic conditions. The reason is that due to the high resistivity (ρ) generally couples with high material constant (B value) in those traditional spinel thermistor ceramics. It is hard to meet the requirement of high ρ and low B in deep cryogenic. The resistivity (ρ) of two-phase composite ceramic is the average value of the two-phase ceramic, and the B value is the lowest value of the composite ceramic. The high ρ low B characteristics of the two-phase composite ceramic have been improved. In view of the synergistic effect of core-shell composite thermistor ceramics, the thermistor material’s resistivity (ρ) can be greatly increased and the B value kept unchanging by optimizing the thickness of shell materials..This proposal selects a core-shell structure LaMxMn1-xO3@BaTiO3-Bi(Me)O3 composite thermistor materials as the research object, which were synthesized by co-precipitation method and sol-gel method. Firstly, by doping LaMxMn1-xO3 with Ba2+ and Sr2+ ions, which reduces the low temperature range and B value. Secondly, it is improved the high temperature range and resistivity (ρ) of the shell materials by Fe3+、Sc3+、(Zn0.5Ti0.5)3+ ion doping Bi (Me)O3 material and adjusting the shell materials’ composite degree. The rule of the heterogenous interface phase diffusion and the mechanism of ion migration of the core-shell thermistor ceramic materials were confirmed, and explore the relationships among composition-structure-performance in LaMxMn1-xO3@BaTiO3-Bi(Me)O3 composite thermistor materials.The cryogenic conductive mechanism of the core-shell composite thermistor ceramics was revealed..The achievements of this project have provided ideas for the preparation of core-shell composite thermistor ceramics and design of new composite thermistor ceramics in different wide temperature ranges.

获得深低温下宽温区热敏陶瓷是目前的难题，这是由于传统尖晶石相热敏陶瓷电阻率ρ高时其材料常数B值亦必大，难以满足深低温下宽温区高ρ低B的要求；双相复合热敏陶瓷的ρ为两相材料平均值，B值为复合材料最低值，改善了热敏陶瓷高ρ低B的特性；鉴于核壳复合材料的协同效应，通过优化包覆壳层材料，可大幅提高热敏材料ρ且使B值不变。.项目以共沉淀和溶胶凝胶法制备核壳LaMxMn1-xO3@BaTiO3-Bi(Me)O3复合材料为对象，先在核材料LaMxMn1-xO3中掺杂Ba2+、Sr2+，降低其低温段及B值；再以BaTiO3复合Fe3+、Sc3+、(Zn0.5Ti0.5)3+掺杂的Bi(Me)O3，提高壳材料高温区间及ρ值；阐明核壳陶瓷异质界面相扩散规律及离子迁移机制，探讨陶瓷组成-结构-性能间相互关系，揭示核壳结构复合陶瓷深低温电荷输运机制。.研究成果对核壳复合热敏陶瓷制备及设计不同宽温区热敏陶瓷提供借鉴

核壳材料具有微观尺度上组分控制及协同效应，是进行新型功能材料开发及可控性设计的重要手段，本项目通过构筑LaMxMn1-xO3@BaTiO3-Bi(Me)O3复合材料，结合XRD、SEM、HTEM等实验结果，系统研究了材料的包覆层厚度（nc/ns）-复合度-结构-电荷输运机制间的相互关系，阐明了核壳结构复合热敏陶瓷体系中金属离子的结构、氧化状态、电子轨道跃迁能级与材料设计、构筑的关系，建立了核壳结构复合热敏陶瓷材料结构、电荷输运、电子态与电阻率ρ、B值等电学参数关联性，揭示了核壳结构复合热敏陶瓷在深低温下的电荷输运机制，获得了可用于-200~200℃宽温区用热敏材料体系，核壳结构热敏陶瓷材料电学参数达到ρ77K=2.6×105Ω·cm, B25/50=1674K，核壳结构材料的研究可为低温宽温区器件的研制提供了科学依据和技术支持。在本项目资助下，本课题共计发表高水平论文13篇，申请国家发明专利4项（其中已授权3项）；协助培养已毕业博士研究生2人，硕士研究生3人。