具有共格/半共格界面和织构结构的ZnO/SrTiO3纳米复合材料的制备及其电热输运性研究

Zinc Oxide is immense potential to be a high temperature thermoelectric material due to the wonderful chemical stability and thermoelectric power factor. However, the electrical and thermal transport is hard to tune which limits the development and implication of ZnO thermoelectric materials. The current project is intended to fabricate the ZnO/SrTiO3 nanocomposites with controllable texture by field activated sintering/hot deformation, the lattice matching is adjusted by teture in order to form coherent/semi-coherent interfaces; To investigate the hot deformation behavior of ZnO/SrTiO3 nanocomposites and the law of ZnO/SrTiO3 interface formation; to explore the pivotal role of the texture development in the process of formation for coherent/semi-coherent interfaces; to reveal the mechanism of hot forging for ZnO/SrTiO3 nanocomposites and formation of ZnO/SrTiO3 coherent/semi-coherent interfaces. To calculate the density of states and barrier for ZnO/SrTiO3 interface by first principles; to establish the correlation between the interface structure and electrical and thermal transport; to reveal the regulation mechanism of electrical and thermal transport for ZnO/SrTiO3 interfaces, in order to realize the collaborative optimization of thermoelectric property by coherent/semi-coherent interfaces and texture.

氧化锌（ZnO）化学稳定性好，热电功率因子高，是极具潜力的高温热电材料。然而其电热输运性难以协同调控，限制了ZnO热电材料的发展和应用。项目拟采用电场辅助热变形技术制备织构可控的ZnO/SrTiO3纳米复合材料，通过织构调控ZnO/SrTiO3面内晶格匹配关系，进而构建ZnO/SrTiO3共格/半共格界面界面；研究ZnO/SrTiO3纳米复合材料的热变形行为和ZnO/SrTiO3界面的形成规律，探明织构变化在共格/半共格界面形成过程中的关键作用，揭示ZnO/SrTiO3纳米复合材料的热变形机制及ZnO/SrTiO3共格/半共格界面的形成机理；基于第一性原理计算ZnO/SrTiO3界面态密度和界面势垒，阐明界面结构与电热输运性之间的关联，揭示ZnO/SrTiO3共格/半共格界面对电热输运性的调控机制，从而实现共格/半共格界面、织构对ZnO/SrTiO3纳米复合材料热电性能的协同优化。

ZnO热稳定性好，具有优异的电学性能和塞贝克系数，是一种极具潜力的高温热电材料。然而，较高的本征热导率严重制约了ZnO热电材料的应用和发展。为实现ZnO热电材料的电热输运性能协同调控，项目以电场辅助热变形技术制备织构可控的ZnO/SrTiO3纳米复合材料为研究目标。重点研究织构ZnO/SrTiO3面内晶格匹配关系，进而构建ZnO/SrTiO3共格/半共格界面界面；通过ZnO/SrTiO3纳米复合材料的热变形行为和ZnO/SrTiO3界面的形成规律，探明织构变化在共格/半共格界面形成过程中的关键作用，揭示ZnO/SrTiO3纳米复合材料的热变形机制及ZnO/SrTiO3共格/半共格界面的形成机理。首先，通过电场活化烧结制备结构致密的Zn0.98Al0.02O/SrTiO3纳米复合材料，其电导率显著增加。纳米SrTiO3与ZnO形成的纳米界面使声子散射增强，热导率降低。SrTiO3含量为2.0 wt.%时，其ZT值为Zn0.98Al0.02O的1.58倍。其次，利用热变形技术制备织构Zn0.98Al0.02O，发现热变形温度是影响织构因子的主要因素。织构因子较低时，电导率随织构因子变化缓慢，织构因子较高时，电导率随织构度变化显著，经过热变形过程的织构Zn0.98Al0.02O陶瓷最高Hall迁移率为100.3 cm2·V-1·s-1，最高电导率为29.5 S/m。织构因子的变化对热导率影响较小，织构因子为0.43时，Zn0.98Al0.02O陶瓷ZT值达到最大。最后，制备织构Zn0.98Al0.02O/SrTiO3纳米复合材料，1123K 热变形温度下， SrTiO3含量为1.0 wt.%的Zn0.98Al0.02O/SrTiO3复合材料的取向因子为0.39，随织构因子增大，电导率大幅度增加，最高达4.0×104 S/m，ZT 值达到最大。本项目已在SCI期刊上发表论文5篇，申请中国发明专利2项，培养硕士研究生2人，项目负责人在国内外学术会议上作报告2次。