Preparation And Properties Of Yb³⁺/Er³⁺ Codoped Tellurite Glasses

Tellurite glasses have unique merits such as low cut-off phonon energy,high refractive index,high RE ions solubility,good physical and chemical stability,for upconversion host materials.In this work,a series glasses of TeO₂-BaF₂/BaCO₃-REF₃?RE=La,Gd,Y?system?TBRE/TBCY?were prepared by traditional melting method.The thermal stability,optical properties,and optical temperature sensing abilities of TeO₂-BaF₂-REF₃ glasses were synthetically studied.Moreover,the crystallization characteristics of TeO₂-BaF₂/BaCO₃-YF₃ glasses were explored.The transparent glass ceramics of TBY and TBCY15 were successfully prepared by adjusting and controlling the heat-treatment schedule and glass component.The specific research contents include the following aspects:?1?Preparation,physical and thermal properties of tellurite glasses.The Yb³⁺/Er³⁺codoped TeO₂-BaF₂/BaCO₃-REF₃ glasses were prepared by traditional melting method.The densities and refractive indices of the tellurite glasses were measured.The thermal properties of tellurite glasses were compared by DSC and thermal expansion curves.Among TeO₂-BaF₂-REF₃ glasses,the TBL performed best thermal stability and highest refractive index.?2?Obsorption spectra and J-O analysis.Based on the absorption spectral,the J-O intensity parameters were calculated by J-O theory,and the spontaneous emission rates,fluorescence branching ratios of the selected emissions and radiative lifetimes of Er³⁺ions on the initial energy levels were further calculated.Compared with other typical glasses,the tellurite glasses have larger values of?₂,suggesting that the bond covalency between Er³⁺ions and ligand is comparably high in the present tellurite glasses.?3?Fluorescence emission,fluorescence decay and upconversion luminescence properties,containing:?1?Excitation spectra.The excitation spectra of the tellurite glasses were measured to help acquire information on the contribution to green and red emissions.?2?Emission spectra.The emission spectra of the tellurite glasses under UV?380 nm?and NIR?980 nm?excitations were measured.The intense green emissions can be seen in the tellurite glasses under two excitation modes.Compared with UV excitation,an enhancement of red emissions was observed under NIR excitation.Specially,the TBG performed a higher value of upconversion integral intensity than other glasses?TBL,TBY?.?3?Fluorescence decay.The fluorescence decay curves of ⁴F_9/2,²H_11/2,⁴S_3/2 levels were measured and discussed in details.The relevant fluorescence lifetimes of emitting levels,the estimated energy transfer efficiencies and fluorescence quantum efficiencies of selected emissions were calculated.The results indicated that those glasses have good luminescence properties.?4?Upconversion luminescence and possible energy transfer mechanisms.The possible energy transfer mechanisms were discussed based on the relation of upconversion intensities versus pump powers.The possible mechanisms of the tellurite glasses are energy transfer process between Er³⁺and Yb³⁺involved two phonons.?4?Temperature sensing ability under UV and NIR excitation modes.Based on the fluorescence intensity ratio?FIR?technique,the upconversion emissions of two thermal coupled levels of ²H_11/21/2 and ⁴S_3/2 of Er³⁺in the tellurite glasses were used for temperature sensing.The maximum sensitivities S_maxax of them are 6.57–6.84×10^-33 K^-1,the temperatures achieved the S_max are 548 K–573K.And the relative sensitivities S_r at room temperature?²98 K?are 1.25–1.28%K^-1.?5?Crystallization properties of the tellurite glasses.The technology for preparing transparent glass ceramics was exploring by optimizing heat-treatment schedule and adjusting glass component.The transparent glass ceramics contained Y₂Te₆O₁₅ were successfully prepared in TBY and TBCY15,respectively.The phase and microstructure of transparent glass ceramics were characterizing by XRD and TEM.The upconversion luminescence of transparent glass ceramics were enhanced compared with precursor glasses.The above upconversion tellurite glasses have potential applications for lighting,flat panel display,solar cell,and temperature sensor.Our research on these materials also provides a reference for exploring the preparation,properties and application of new rare-earth doped tellurite glasses.