Preparation And Property Studies On Bismuth Vanadate Based Semiconductor Functional Materials

Bismuth Vanadate is an excellent semiconductor material. It has attracted wide attention owing to its unique crystal structures and performance. But the research of BiVO4single crystal and polycrystalline ceramic are very little. For lack of its intrinsic properities, the preparation process and performance of BiVO4based crystals and ceramics were studied in this paper. The main contents are as follows.Chapter one is the introduction. Firstly, the crystal structure and basic properties of BiVO4were briefly introduced. Then, both the research progress of BiVO4and PTC effects were reviewed in detail. Lastly, the background and research significance were introduced and the main researching contents of this dissertation were presented.Chapter two mainly studies the growth and properties of BiVO4crystal by Bridgman method. It was firstly found that, light illumination can induce water wettability changes upon the mono clinic phase BiVO4crystal surface.Chapter three studies the effects of sintering conditions on phase composition, microstructure, dielectric, and resistance for the BiVO4ceramic. The glass phase was generated on the surface of BiVO4ceramic when the sintering temperature was higher than820℃. It was also found two loss peaks in the dielectric relaxation curves. And BiVO4ceramics showed significant PTC effect and the underlying influence of ceramic microstructures was discussed.Chapter Four studies the effect of doping ratio of La3+on electrical properties for Bi1-xLaxVO4ceramic. The dielectric loss and electrical conductivity can significantly decrease by La3+doping. The current transfer mechanism was different at low and high temperature areas, for the lgp-T curve of Bi1-xLaxVO4(0.05≤x≤0.20) ceramics have turning point near200℃.Chapter five studies the effect of V5+site doping with M6+(M:Mo、W) on electrical properties for BiVO4ceramic. The dielectric loss significantly decreases by Mo6+doping. The dielectric frequency spectra of Bi1-x/3Φx/3V1-MoxO4ceramic have two dielectric loss peaks with typical relaxation characteristics. The resistivity of Bi1-x/3Φx/3V1-xWxO4ceramic was significantly changed by W doping. The PTC effect is very obvious. The resistance has increased2-3orders of magnitude for the Bi1-x/3Φx/3V1-xWxO4ceramics when x=0.06or0.18. Chapter Six summarizes the main results and innovations in the dissertation. The research tendency of BiVO4material was outlooked as well. Figure [35] table [5] reference [100]...