Preparation And Photoluminescence Of Rare Earth Doped Borosilicale Glass With UV Conversion Performances

With the development of society and rapid technological progress, the ultravioletlight conversion materials have been attracting more and more attention due to itswide range of applications in many fields, such as ultraviolet detection technology,enhancing the efficiency of solar cell, the new type of lighting source and ecologicalagriculture. However, the limitations of absorption and application on ultravioletspectrum, especially near ultraviolet, are still remained by the narrow excitation bandand low light conversion efficiency. In order to improve the light conversionefficiency, one of the most important means is getting the ultraviolet light conversionmaterials with wider excitation bandwidth which can enhance the light absorptionefficiency on the broadband range.While, rare earth doped fluoro-borosilicate glass or glass-ceramics exhibits theexcellent optical properties including high refractive index, low dispersion and goodtransparency in the UV, visible and IR regions. Glass or glass-ceramic can be directlyused in many devices, due to their relatively simple fabrication process and lowproduction cost. However, current few investigations are reported and methods ofimproving the luminous efficiency method are relatively simple on the ultravioletband excitation in the glass and glass-ceramics.To improve the UV light conversion efficiency and excitation bandwidth by thedeposition of ZnO quantum dot with the sensitization of Eu³⁺on the appropriateenvironment, the main method is adopt by changing the local environment andenhancing the excitation bandwidth of Eu³⁺. The innovation of the paper are the use ofdifferent synthesis methods to produce the transparent optical glass which is expectedto be a new type of UV light conversion material, and the study of the transfermechanism of energy between the rear earth ions and the matrix on light-emittingprocess. The main works of this paper are as follows:In order to achieve the change of the local environment of Eu³⁺, we adopted themelting synthesis method to produce the boron silicate fluoride oxide glass with thecomposition of （40-x）ZnO-x ZnF₂-40B₂O₃-10SiO₂-5K₂O-5CaO-10Al₂O₃: Eu₂O₃（x=0,10,20,30, and40mol%）. We have analyzed the structure and the opticalproperties of the synthesized glass by the detailed characterizations （XRD, FTIR andPL）. The ZnF₂content dependent glass structure has been discussed based onfourier-transform infrared spectroscopy. The influence of ZnF₂/ZnO ratio on theoptical properties of Eu³⁺-doped fluoro-borosilicate glass has been investigated. It isfound that the red emission increases with the enhancement of ZnF₂/ZnO ratio.Results show that The Judd–Ofelt （J-O） parameters （2,4） have been evaluatedfrom the recorded emission spectra. The2and4parameters increase with theZnF₂/ZnO ratio, which is due to the reduced symmetry of Eu³⁺sites.Eu³⁺doped ZnO-SiO₂glass-ceramics embedding ZnO quantum dots （QDs） weresuccessfully prepared by a sol-gel method followed by the annealing process. Suchglass ceramics show a high transparency in the visible-infrared range. Meanwhile,Eu³⁺doped ZnO-SiO₂transparent glass-ceramics embedding ZnO quantum dots （QDs）were successfully prepared by the sol-gel method. The Eu³⁺and ZnO concentrationand annealing process dependent spectrum properties and glass structure has beeninvestigated. The sensitization of ZnO quantum dots to Eu³⁺is verified. Resultsindicates that the emission intensity increases with the enhancement of ZnO contents.After annealing at600℃, the glass-ceramics show good ZnO-quantum-dots sensitizedluminescence properties. Orthogonal experiment suggest that the optimal sensitizationluminescence appears at ZnO concentration of15-20%and Eu³⁺concentration of2%.