Preparation And Optical Properties Of ZnO Powder

Luminescence materials are widely used in daily life and production. Developing alow cost, environmental security and good luminous performance powder materials haspractical application values. Zinc oxide, a new type of semiconductor luminescencematerials with forbidden bandwidth of about3.37eV at room temperature, has as much as60meV of baryon binding energy. ZnO has significant application prospect inphotoelectric field. In order to obtain the ZnO powder with excellent luminescentperformance, this paper optimized the process of ZnO powder by the single factorexperiments method and surface modification or doping modification.We mainly investigate the relationship between the synthesis process and luminousproperties of ZnO powder in this paper and discuss the luminescence mechanism of ZnO.Surfactant PEG6000, SDS, CTAB and L-G modification and rare earth La, Ce dopingmodification effect on the crystallization and luminescence of ZnO were studied. And themethods for improving ZnO powder luminous intensity were discussed. The obtainedsamples were characterized by TG-DTA、XRD、PL、SEM、UV-Vis、FT-IR, and the mainresearch contents and conclusions are as follows.（1） The ZnO powders were synthesized by direct precipitation method with Znicacetate and ammonium oxalic acid as raw materials. XRD analysis showed that theprecursor is ZnC₂O₄·2H₂O; ZnO powder was hexagonal wurtzite structures after roasting;The TG-DTA analysis showed that the lowest decomposition temperature is400℃.Through the single factor experiments we known that the luminous intensity was relatedwith the crystalline of ZnO powders and its defect levels, also the high crystallinity andlow defect levels are helpful to improve the luminous intensity. The light-emittingmechanism of photoluminescence peaks in ZnO powder at room temperature wereanalyzed. The peak of391nm was caused by free exciton recombination luminescence,and the peak of405nm was caused by bound exciton recombination luminescence.（2） Adding surface active agent or doping rare earth was researched to improve theluminous intensity of ZnO powder.The influences of four kinds of surfactants on the crystal particle and luminescenceproperties of ZnO powder were studied. The results showed that the ZnO powder was hexagonal system wurtzite structure, and the primary particle size and the dispersion ofpowders increases while the particle size decreases after adding surfactants.The surfactantsof PEG6000, CTAB and L-G can improve the crystallinity and luminous intensity of ZnO.The luminous intensity of ZnO was the highest after adding PEG6000.The influences of doping La and Ce on the crystallization and luminous properties ofZnO powder were studied. The results showed that moderate amount of the rare earthdoped ZnO powder was hexagonal system wurtzite structure, and rare earth ions into thelattice at low doping concentration while appear new phase at high doping concentration;Compared with pure ZnO powder, when doping amount at0.3mol%, the ZnO powder’luminous intensity was improved obviously. La doped ZnO powder luminous intensity washigher than Ce doped ZnO powder.