锰铁酸钇基多铁性陶瓷的微观结构和电、磁性能

Searching for room-temperature multiferroic materials with single phase has always been the hot research topic in the field of materials science and condense matter physics. Hexagonal YMnO3 has attracted much scientific attention because of its relatively high ferroelectric transition temperature (about 950 K). By partially substituting Mn for Fe in YMnO3, the room-temperature ferroelectric property can be maintained and the the relatively low magnetic transition temperature of YMnO3 (about 77 K) can be increased to room-temperature or higher. However, because of Fe introducing into YMnO3, the dielectric loss and leakage current are also increased, and this hinders the applications in the field of information. In this study, partial positive-ions substitution and control of oxygen vacancy concentration will be carried out in YMn1-xFexO3 ceramics to change the microstructure.By thoroughly investigating the microstructure, multiferroic, dielectric and leakage properties of YMn1-xFexO3 based ceramics, the dependence of electrical and magnetic properties on the microstructure will be clarified，and then the structural and physical origins for the electrical and magnetic properties will be indicated.On this basis, the controlling principles of structure and property will be discussed.This study will provide theory evidence for optimising the electrical and magnetic properties of YMn1-xFexO3 based ceramics, and lay the foundation for the development and application of YMnO3 based single phase multiferroic materials.

寻找室温单相多铁性材料近年来一直都是材料科学和凝聚态物理领域的研究热点。备受关注的六方锰酸钇（YMnO3）具有较高的铁电转变温度（约950 K），且通过Fe部分置换YMnO3中的Mn可以在保持室温铁电性的同时将其较低的磁性转变温度（约77 K）提高到室温以上,然而因为Fe的引入也将使YMnO3的介电损耗和漏导电流增大，阻碍其在信息领域的应用。基于此，本项目拟对锰铁酸钇（YMn1-xFexO3）陶瓷进行阳离子部分置换和氧空位浓度控制来改变其微观结构，并通过系统研究YMn1-xFexO3基固溶体陶瓷的微观结构、多铁性、介电性能及漏导性能来阐明其电、磁性能随微观结构变化的规律，以揭示其电、磁性能的结构根源与物理本质。在此基础上，探讨YMn1-xFexO3基陶瓷的结构性能调控原理，为其电、磁性能优化提供理论依据，并为YMnO3基单相多铁性材料的发展与应用奠定基础。

本项目采用不同价态离子对锰铁酸钇多铁性陶瓷进行部分置换。采用低温固相反应法在较低的煅烧温度下制备出单相粉体，经高温烧结后制得较致密的固溶体陶瓷。研究了不同价态离子置换对锰铁酸钇陶瓷微结构和电、磁性能的影响。结果表明，进行离子部分置换后，陶瓷内部的磁性离子价态分布发生明显改变，导致陶瓷的磁性转变温度和低温磁有序结构发生明显变化。研究中采用的较高价态离子置换铁锰酸钇陶瓷后，其介电损耗降低，电阻率增大。另一方面，本项目研究了制备条件对锰铁酸钇多铁性材料性能的影响，并对铁锰酸酸钇陶瓷进行了气氛退火处理，研究了氧空位浓度对陶瓷微结构和性能的影响。结果表明，采用传统固相反应法，预烧后粉体和烧结后陶瓷的室温磁性能存在明显差异。经氮气氛处理后，陶瓷低温下的弱铁磁性减弱且团簇玻璃态行为消失，其介电损耗增大，电阻率下降。这主要是由于磁性离子的价态分布和氧空位浓度变化共同作用引起的。本项目的研究结果可以为锰铁酸钇体系多铁性陶瓷的磁、电性能优化提供实验数据和理论指导。