Preparation And Photoluminescence Of ZnTiO₃Powders

Luminescence is a process during which the energy is absorbed by the internal partof an object in some way and then transformed into light radiation. Photoluminescence isa phenomenon which the light-emitting materials can produce radiation when stimulatedby ultraviolet, visible or infrared light. It has important research and practical value.Photoluminescence materials can be used to produce luminous ink or paint, andlight-emitting plastic, cement, glass or ceramic. Therefore photoluminescence materialplays an important role in the field of architectural decoration, emergency lighting,security signs, military products, and light chemical products. Zinc titanate has beenwidely investigated for applications in many fields. It’s also one kind of potentialphotoluminescence materials. However, most of the reports in recent years focus theirattention on luminescent property of the cubic-ZnTiO₃. So, we present the luminescentproperty of hexagonal ZnTiO₃in this work. Our researches are as follows:Firstly, preparing pure hexagonal ZnTiO₃powders in sol-gel process. In order toinvestigate the evolvement of the precursor as-prepared in the process of heat-treatment,the phase constituent, the powder morphologies of the calcined samples and theluminescent property, thermal analysis of dry gel powders was performed bythermogravimetric and differential thermal analysis. The calcined samples werecharacterized by X-ray diffraction. The microstructure was observed by field-emissionscanning electron microscope. The Fourier-transforming infrared spectroscopy of thecalcined powder was performed on dispersion in potassium bromide using thepressed-disk method. And the measurement of excitation and emission spectra wasperformed with fluorescence spectrophotometer.Secondly, preparing hexagonal ZnTiO₃powders doped Ni²⁺in sol-gel process. Thecalcined samples were characterized by X-ray diffraction. And the measurement ofexcitation and emission spectra was performed with fluorescence spectrophotometer.Then comparing this result with pure hexagonal ZnTiO₃’s.Thirdly, preparing pure cubic-ZnTiO₃powders in sol-gel process. The calcinedsamples were characterized by X-ray diffraction. And the measurement of excitation andemission spectra was performed with fluorescence spectrophotometer. Then comparingthis result with pure hexagonal ZnTiO₃’s.The results are as follows:（1）Nanometer scale ZnTiO₃powders with pure hexagonal phase were synthesizedby adopting sol-gel process using deionized water as solvent for the first time. The purehexagonal phase could exist in a relatively wide temperature range of550⁹00℃. Theparticle size of ZnTiO₃calcined at550℃is about50nm. （2）The excitation peaks of the samples show similar characteristics for alltemperatures. It presents a sharp excitation band with a maximum around255nm. Butthe PL band of all samples consists of two PL peaks, one is very strong and situates at450nm and the other is very weak and situates at600nm. And the intensity of the peaksgrew up with increasing temperature. It was found that the light emitting of ZnTiO₃wasresulted from O2vacancy and Zn2+vacancy.（3）ZnTiO₃doped with Ni²⁺ion were prepared by sol-gel process using deionizedwater as solvent at600℃. It revealsthat the introduction of the dopants does not changethe phase composition, both the doped and the undoped samples exhibit a hexagonalZnTiO₃crystal structure.（4）The introduction of Ni²⁺ion has changed ZnTiO₃nanocrystal into a newluminescent material. The relative intensity yields a maximum when Ni²⁺ionconcentration is3.0%. The Ni²⁺ions substitute for the site of Zn2+.（5）Pure cubic-ZnTiO₃has been synthesized by sol-gel method at a lowertemperature of600℃. The pure phase could exist in a relatively wide temperature rangeof600⁷00℃.（6）The excitation wavelength of the cubic-ZnTiO₃is297nm. Both the intensityand the position of the peaks change with increasing heat-treated temperature. Thedifference of luminescent property between cubic and hexagonal ZnTiO₃is likely to bethe difference of crystal structure.