Study On Preparation And Photocatalytic Properties Of Zinc Gallate Powders

ZnGa₂O₄is an important p-block semiconductor material with extensiveapplications in flat panel display, thin film electroluminescence display, andvacuum florescent display. Furthermore, on account of better chemical stabilityover sulfide phosphors, ZnGa₂O₄can endure a high electron beam current.Moreover, ZnGa₂O₄has excellent performance in waste water purification andthe degradation of benzene. Based on those applications of ZnGa₂O₄onphotocatlyic, the preparation of ZnGa₂O₄powders by hydrothermal and EDTAcomplexation sol-gel process is investigated systemically in the paper.The as-prepared ZnGa₂O₄samples were characterized by X-ray diffraction（XRD）, Scanning electron microscope （SEM）, Field emission scanning electronmicroscope （FE-SEM）, Transmission electron microscopy （TEM）,Thermogravimetric-differential thermal analysis （TG-DSC）. The effects oftechnological parameter on the phase compositions, the microstructure and thephotocatalytic activity were investigated. The results show that:（1） ZnGa₂O₄crystallites were synthesized via a hydrothermal method usingZnSO4·10H2O and Ga2O3as source materials at the condition of temperaturerange of160-200oC, the pH value of13.5and autoclave filling ratios of65%. Itwas found that their morphologies changed from nano spheric particles to theself-assemble three-Dimensional structures with the increase of hydrothermaltemperature; the bigger size and denser surface structure are observed, when thehydrothermal time increased. The photocatalytic degradation test showed thatthe best photodegradation efficiency was the sample prepared at160oC, and the degradation constant Kcwas0.06885min^-1. The best photodegradationefficiency was the sample obtained at hydrothermal time of6h.（2） Those small octahedral and self-assembled three-Dimensional structureof ZnGa₂O₄particles could be conveniently synthesized by hydrothermalmethod with the aid of CTAB. It was found that CTAB surfactant in which theaddition is1%play an important role in formation of ZnGa₂O₄octahedralcrystallites and three-Dimensional rodlike structures. The photocatalyticdegradation test using rhodamine B as a model pollutant showed that thephotocatalytic activity of the ZnGa₂O₄crystallites assisted with CTAB can besignificantly decreased with temperature increasing and the bestphotodegradation efficiency was the sample prepared at160oC and theirmorphologies are octahedral crystallites, of which the degradation efficiencywas97.6%in60min.（3） The ZnGa₂O₄crystallites can be obtained at calcining temperature of650-800°C using the zinc acetate and gallium oxide as source materials, withthe ethylenediamine tetraacetate for complexing agent. The samples exhibit theoctahedral structure at700°C and the rodlike morphology at800°C. With theincrease of temperature, its photocatalytic performance for degradation ofrhodamine B is increased.（4） The single crystalline of ZnGa₂O₄with the octahedral structure can beobtained at calcining temperature of700°C from4h to6h. The preparationprocess of ZnGa₂O₄with the octahedral structure is controlled by the generatingrate of ZnO. According to the degradation of rhodamine B tests, the octahedralZnGa₂O₄crystallites display good photocatalytic performance.