Controllable Preparation And Characterization Of Metal Molybdate Luminescent Materials

In this thesis, solution-based chemical routes were developed to synthesize molybdates powders; controllable synthesis metal molybdates powders with different sizes and morphologies were carried out via mild and simple approaches through investigating preparation methods and experimental conditions; as-prepared molybdates powders with special morphology and size were characterized to check their photoluminescence performance. The main points are summarized as follows:(1) CdMoO4 crystallites with varying morphologies can be synthesized via a simple hydrothermal process without any organic additives or templates, using Cd(NO3)2.2H2O and Na2MoO4.2H2O as raw materials. The powders produced were characterized by using XRD, SEM and PL. Studies on the reaction time, reaction temperature and the initial pH value in the hydrothermal process were made. It was found that the initial pH value played a key role in the crystallization and development of CdMoO4 crystallites with special morphology. The PL spectra showed that the floccule-like particles prepared under high basic hydrothermal condition took on the best luminescence property.(2) BaMoO4 crystallites with controlled dimensions ranging from nanoparticles to microcrystallite were successfully synthesized by Na2H2EDTA-assisted precipitation reaction at room temperature, using BaCl2.2H2O and Na2MoO4.2H2O as raw materials. Studies on the amount of Na2H2EDTA and reaction time in the aqueous precipitation reaction were made. The powders obtained were characterized by using X-ray diffractometer (XRD), a scaning elecron microscope (SEM),a transmission electron microscope (TEM), a Energy Dispersive X-Ray Fluoresence Spectrometer (EDX) and photoluminescence spectra (PL). All the analysis indicated that the Na2H2EDTA played a key role in the crystallization process. The PL spectra of the BaMoO4 crystallites with different dimensions at room temperature show that the dimensions of materials have influence on their photoluminescence property.(3) BaMoO4 crystallites with varying morphologies were successfully synthesized via a simple hydrothermal process without any organic additives and templates with using BaCl2.2H2O and Na2MoO4.2H2O as raw materials. Studies on the reaction temperature, time and the initial pH value in the hydrothermal process were made. The powders obtained were characterized by using XRD, SEM and PL. All the analysis indicated that the initial pH value played a key role in the crystallization and the morphology evolvement of BaMoO4 crystallites. The PL spectra showed that double-taper-shaped crystallites with higher aspect ratio exhibited better luminescent property than those with lower aspect ratios.