Synthesis Of New Bisumth&Vanadium Oxides-Based Micro-nanostructures And Their Properties Investigation

The goal of this dissertation is to develop novel chemical reaction routes for controlling synthesis of new bismuth or vanadium-based layered compounds with micro-nanostructures via analyzing the crystal structural characteristics of the objective products and study the corresponding performance of the synthetic bismuth or vanadium-based layered compounds with micro-nanostructures, such as electrical property and magnetism. Also, the related structure-property relationships have been also researched in this dissertation. The details are summarized briefly as follows:1. Based on the synthesis of the typical layered structure VO2·0.5H2O, a simple and mild hydrothermal route was proposed to prepare the VO2·0.5H2O microstructural products. Electrical and magnetism properties as well as the influence of their microstructures on properties are investigated. Electronic features carried out by the temperature dependence of resistivity indicate as-prepared VO2·0.5H2O behaves as semiconductor. From the crystal structure point, the semiconductor behavior originates from the z-type vanadium chains in the critical value of V-V interaction, where the electronic orbits overlap each other. The abnormal jump is observed in M-H curve. Fitted by Curie-Weiss law, strong antiferromagnetism is found between two neighboring V ions. We further investigated the application of as-prepared products in the aqueous lithium ion batteries. The results indicated it has high first discharge capacity and cycle stability. The quadruple VO6octahedra share the edges each other and no channels in layers and high stability of as-prepared crystals lead to the cycling stability of electrochemical properties2. We presented a facile and chemical strategy to synthesize pure nonstoichiometric Bi2O2.33nanoflowers by a solvothermal method. The magnetic property of the synthetic Bi2O2.33nanoflowers was investigated and the first observation of their room temperature ferromagnetism was reported. We noted that Bi2O2.33is a typical nonstoichiometric compound including a number of oxygen defects. For charge balance, Bi2+ion should exist in nonstoichiometric Bi2O2.33compound similar to Ti2+, Ti3+in TiO2-x. Since the XPS, EDX and XRD studies confirm the absence of any impurity present and some secondary phases in our samples, ferromagnetism observed in the present case is not likely to be caused by the unintentional doping. According to the results of XPS spectra, the oxygen defect-induced Bi2+with an unpaired electron Bi2+should be responsible for ferromagnetism in the Bi2O2.33nanoflowers. Moreover, the bonding between the bismuth pairs makes the charge transfer between Bi and Bi possible. Meanwhile according to the bound magnetic polaron model, this charge transfer favors an enhancement of curie temperature Tc to achieve the room-temperature ferromagnetism in Bi2O2.33.3. As a new inorganic graphene-like material, ternary compound calcium vanadate (CaV4OO9) ultrathin nanosheets have been reported for the first time. X-ray powder diffraction (XRD) result revealed that the used ultrasonication waves trigger the arrangements and enhance the c axis orientation in the formation of high-quality two-dimensional nanosheets. Transmission electron microscopy (TEM), atomic force microscopy (AFM) and Raman results confirmed that ultrathin nanosheets have atomic thickness and maintain the integrity of the plane structure without obvious deformations. These CaV4O9ultrathin nanosheets would provide an ideal two-dimensional material platform to investigate their new potential electronic, magnetic and optical behavior.