Synthesis Of Tungstates And Molybdates Nanoparticles By Molten Salt Method And Hydrothermal Method

Tungstates and molybdates are two important families of inorganic material that have a high application potential in various fields, such as in photoluminescence, microwave applications, optical fibers, scintillator materials, humidity sensors, magnetic properties, and catalysis. The method of synthesis of tungstates and molybdates is a traditional high-temperature solid-state reaction, which has some disadvantages, e.g. apart from high temperature and prolonged reaction time being needed, the traditional high-temperature solid-state reaction generally results in larger particles in size with irregular morphology, and inhomogeneous chemical composition. Other methods, such as sol-gel, co-precipitation, microemulsion and citrate complex method, but these methods still have some disadvantages, such as complex, the use of large amounts of organic solvents, unfriendly to the environment, large in size with irregular morphology and inhomogeneous composition. Therefore, this thesis, mainly focuses on the following research works to prepare tungstates and molybdates powders under a mild condition.1. For the first time CaWO₄ nanoparticles were successfully synthesized at 200℃and CaMoO₄ nanoparticles synthesized at 270℃by a molten salt method, respectively; CdWO₄ and CdMoO₄ were synthesized at 70℃by a hydrothermal method, respectively;2. According to the PL analysis of the as-prepared powders, with the excited wavelength at 360 nm, CaWO₄ emission peak at 521 nm was observed; and with the excited wavelength at 356 nm, CaMoO₄ emission peak at 508 nm was observed, respectively. Furthermore, the smaller the size of CaWO₄ and CaMoO₄ is, the stronger the emission intensity is;3. With the excited wavelength at 356 nm, emission peak of the CdWO₄, prepared by the molten salt method, at 528 nm was observed,and the intensity of the PL emission of the CdWO₄ nanorods was much stronger than that of the CdWO₄...