钶铁矿型MnNb2O6的熔盐法合成、钒掺杂与磁性研究

采用了熔盐法新工艺制备了纯相与掺钒的MnNb₂O₆粉晶,利用X射线衍射仪(XRD),扫描电子显微镜(SEM),能谱分析(EDX),透射电子显微镜(TEM)、高分辨透射电镜(HRTEM)和电子衍射(SAED)分析了其物相、形貌及微结构.结果表明合成产物为正交晶系钶铁矿型MnNb₂O₆;在不同的熔盐中合成出了棒状、片状与长方体形貌的纯相产物.讨论了温度与掺杂对结构与形貌的影响,HRTEM与SAED分析表明了产物的各向异性生 关键词： 熔盐法 结构与形貌 掺杂 反铁磁性

Molten salt synthesis, V-doped and magnetic properties of columbite MnNb2 O6

A novel molten salt synthsis technology is developed to prepare single phase and V-doped MnNb₂O₆powder. The prepared samples are characterized by XRD, SEM, EDS, TEM, HRTEM and SAED. The results show that the MnNb₂O₆ powder has an orthorhombic structure_.and the samples prepared in different molten salts exhibit different shapes:flake shape, rod shape, and rectangular shape. The effects of temperature and doped on structure and morphology are discussed. HRTEM and SAED indicate the rod-shape MnNb₂O₆ has the properties of anisotropic growth and crystalline integrality. Magnetic properties are measured by superconducting quantum interference device (SQUID) in a temperature range of 2—30 K under a magnetic field of 2T. The magnetic measurement results indicate that MnNb_1.8V_0.2O₆ undergoes an antiferromagnetic transition with a Néel temperature of 5.4 K. Above 20 K, the inverse susceptibility is fitted well to the Curie-Weiss law θ=-33.9 K,C=10.52 K emu mol ·f.u.^-1 and effective moment 5.82 μ _{B can be obtained. With V-doped amount increases, antiferromagnetic interaction increases. According to the Anderson model, the MnNb2-xVxO6 is antiferromagnet in a low temperature range, which is induced by the superexchange interaction of Mn²⁺-O^2--Mn²⁺.}