钙钛矿型CeTaN_(2)O的高压制备及其磁性和电学性质

High-pressure synthesized perovskite-type CeTaN_(2)O and its magnetic and electrical properties

最近研究发现,AB(N,O)_(3)型钙钛矿氧氮化物具有优异的介电、铁电、光催化等性能,在光电子、能源存储和通信等领域展现出广阔的应用前景.但是,目前该类型材料的制备工艺耗时较长且产物纯度较低.本文以氧化物为前驱体、以氨基钠为氮源,利用六面顶压机设备所提供的高温高压环境成功制备了高纯度的钙钛矿型氧氮化物CeTaN_(2)O块体材料,并将制备时间缩短至1 h,实现了快速合成.并对其晶体结构以及物理性质进行了系统的研究.X射线粉末衍射实验和Rietveld精修结果表明,所制备的样品属于正交晶系,空间群为Pnma.X射线吸收谱测试确定了样品的电荷组态以及阴离子组合为Ce^(3+)Ta^(5+)N_(2)O.磁性和比热测试表明,样品属于反铁磁物质,磁相变温度低于2 K.电学输运性能测试表明,样品的电阻率呈现出典型的半导体行为,且符合三维变程跳跃模型.

Recently,it has been discovered that the AB(N,O)_(3)-type perovskite oxynitrides exhibit excellent dielectric,ferroelectric,and photocatalytic properties,promising for applications in the fields of optoelectronics,energy storage,and communication.Due to the differences in charge,ionic radius,and covalent bonding between N^(3-)ion and O^(2-)ion,the N substitution for O enhances the B(N,O)_(6) octahedron tilting,giving rise to exotic properties and functionalities.However,the current fabrication process for this type of material is rather timeconsuming,leading to products with an appreciable quantity of impurities.In this study,using oxide precursors and sodium amide as the nitrogen source,high-purity perovskite-type oxynitride CeTaN_(2)O bulk materials are successfully synthesized under high-temperature and high-pressure conditions provided by a cubic-anvil press.The synthesis time decreases to 1 h,achieving rapid production.The lattice structure and physical properties of the obtained samples are comprehensively investigated.X-ray powder diffraction experiments and subsequent Rietveld refinement indicate that the title material shows an orthorhombic crystal structure with the space group of Pnma.The X-ray absorption spectra confirm the charge configuration and the anion composition as Ce^(3+)Ta^(5+)N_(2)O.Magnetization and specific heat measurements reveal that the exchange interactions are mainly antiferromagnetic,with a potential magnetic transition below 2 K.The electrical transport data demonstrate typical semiconductor behaviors,which can be further explained by a three-dimensional variable-range hopping model.Our study paves the way for putting this exotic perovskite oxynitride into practical applications.