锰、铁、钴巨介电氧化物的载流子输运特征和介电损耗调控研究

Materials with high dielectric constants are widely used in technological applications like wireless communication systems, such as cellular phones, and global positioning systems, namely as capacitors, resonators, or filters. High dielectric constants allow smaller capacitive components, thus offering the opportunity to decrease the size of electronic devices. Many of Mn, Fe and Co based perovskite-type and K2NiF4-type oxides show a giant dielectric constant. Since weakly bound carriers and slow polarizations present in these oxides, in this proposal, the giant dielectric response, low- and high-temperature dielectric relaxation, as well as the conductivity of Mn, Fe and Co based simple oxides and complex oxides are investigated firstly. The relaxation characteristic and carrier transport mechanism are discussed according to the migration and hopping of weakly bound electrons and oxygen vacancies. Secondly, influences of the different metal ions and their valence state, lattice distortion on the transports of localized electrons and oxygen vacancies, as well as temperature/frequency region of the loss peak are summarized, then propose suitable methods to decrease conductivity and modify interface polarization. Finally, leakage current and interface polarization are adjusted by cation/anion doping and heating treatment process which modifies the defect concentration, transport behavior of carriers and interface characteristic of Mn, Fe and Co based perovskite-type and K2NiF4-type oxides, then dielectric loss is expected to be decreased. Consequently, this project, on the one hand, develops new methods to decrease the dielectric loss of giant dielectric materials, on the other hand, it provides technical support for the efficient use of nonferrous metal resources in Guangxi Zhuang Autonomous Region.

很多锰、铁、钴构建的钙钛矿型氧化物和K2NiF4型氧化物都具有极高的介电常数，但与之伴随的还有很高的介电损耗，从而导致该类材料难以得到应用和推广。针对这些氧化物中存在弱束缚载流子和慢极化的特点，本项目首先研究锰、铁、钴的简单氧化物和复杂氧化物的巨介电响应、低温和高温介电弛豫以及电导行为，从束缚电子和氧空位输运的角度探索它们介电弛豫的特征和载流子输运的机制。其次建立金属离子的类型和价态、晶格畸变等对弱束缚电子和氧空位的短程跳跃和长程迁移的影响机制，及其对损耗峰出现的温区和频段的调控机制，探索降低电导和改善界面极化的方法。最后通过阴/阳离子掺杂和热处理工艺调整材料中的点缺陷浓度、载流子输运行为和界面特征，以此改变漏电流和调整界面极化，从而降低介电损耗。通过本项目的研究，一方面有望为降低巨介电常数材料的介电损耗提供新思路；另一方面有望为广西丰富的有色金属资源的高效利用提供技术支持。

在该项目的支持下，按照项目任务书，深入细致地研究了过渡金属Fe、Nb、Ti、Mn等离子构建的氧化物及其介电响应。从束缚电子和氧空位输运的角度探索了介电弛豫的特征和载流子输运的机制。从价态、晶格畸变角度研究了弱束缚电子和氧空位的短程跳跃和长程迁移及其对损耗峰出现的温区和频段的影响。通过阳离子掺杂和热处理工艺调整材料中的点缺陷浓度、载流子输运行为和界面特征，以此改变漏电流和调整界面极化。项目从微观上理解这些过渡金属离子的价态、离子半径、占位等对简单氧化物和复杂氧化物巨介电弛豫和载流子输运的影响规律。揭示Mn、Fe、Co、Al、Cu、W和稀土等离子在不同晶体结构的介质材料中所扮演的角色以及对电子输运的影响，进而通过调控缺陷结构和阳离子类型来移动介电损耗峰或者降低材料室温附近的介电损耗，达到从微观层面调控巨介电材料介电损耗的目的。在国外学术杂志发表SCI收录的学术论文22篇，其中影响因子大于2的13篇，获得授权国家发明专利11项，实施专利转让2项。培养研究生9名，其中与北京大学联合培养1名，与法国拉罗谢尔大学联合培养1名，与拉罗谢尔大学进行研究生短期学术访问（大于1个月）4人次。培养青年教师3人。