Fabrication And Luminescence Properties Of Rare Earth Ions Doped Yttria Ceramics

Because of high melting point,high thermal conductivity and optical transparency over a broad spectral range,yttria?Y₂O₃?transparent ceramics are promising materials for high-pressure gas discharge lamp,windows,scintillation ceramics and laser ceramics.Studies have shown that the sintering temperature is higher than 1700?,the requirement for equipment is higher and the cost is high.Therefore,exploring a new method to fabricate Y₂O₃ transparent ceramics is one of the research foucuses in recent years.Moreover,Y₂O₃ ceramics have the advantages,such as heat-resisting,corrosion resistance and light weight.Based on the upconversion luminescence using a fluorescence intensity ratio technique,the Y₂O₃ porous ceramics doped with rare earth ions can be used as optical temperature sensors in high temperature and harsh environment.Based on the above background,this paper has made research on the following aspects:1.Tm³⁺,Yb³⁺co-doped Y₂O₃ translucent ceramic was fabricated by sintering method using YOF:Tm,Yb powders.The crystal structure,morphology of the YOF:Tm,Yb powders,microstructure,elemental composition,transmittance spectrum and upconversion luminescence were investigated.The experimental results showed that YOF was completely changed to Y₂O₃ during the sintering process.The full dense microstructure was obtained and there were few micro pores in the ceramics.The ceramic has good transparency in the range of 400¹100 nm and shows strong blue upconversion emission under 980 nm LD excitation,which was ascribed to Yb³⁺?Tm³⁺energy transfer.2.Y₂O₃:Eu³⁺translucent ceramics were prepared by using YOF:Eu³⁺nanopowders as raw materials and BaF₂ nanopowders as sintering aids.The effect of the BaF₂ aids on the microstructure,transmittance and luminescence of the Y₂O₃:Eu³⁺ceramics was investigated.The results showed that with the increase of the BaF₂ additives percentage,the porosity decreased firstly and then increased,but the transmittance was just the opposite,the excitation band of the charge transfer state of Eu³⁺ions moved towards short wavelength,and the emission intensity of Eu³⁺ions firstly decreased and then increased.When the addition of BaF₂ is 1.0wt%,the porosity is the lowest and the transmittance is the best.3.Y₂O₃:Er³⁺translucent ceramics were prepared by using YOF:Er³⁺nanopowders as raw materials and La?OH?₃ nanopowders as sintering aids.The effect of the La?OH?₃aids on the microstructure,pore size,transmittance and upconversion luminescence of the Y₂O₃:Er³⁺ceramics was investigated.The results showed that with the increase of the La?OH?₃ additives percentage,the porosity and cut-off wavelength of transmittance firstly decreased and then increased,but the transmittance was just the opposite.When the addition of La?OH?₃ is 5 mol%,the porosity is the lowest and the transmittance is the best.Under 980 nm LD excitation the Y₂O₃:Er³⁺ceramics show strong green upconversion luminescence,which was ascribed to excited state absorption of Er³⁺ions.4.The porous Y₂O₃:Ho,Yb ceramic was fabricated by hot-press sintering method using Y₂O₃:Ho,Yb nanopowders as raw materials and NaF as pore-forming agents.The crystal structure,microstructure,porosity,elemental composition,upconversion luminescence and temperature sensing behavior were investigated.The results showed that the total porosity was high to be 27.05%with mainly open pores and the pore size was 4⁸?m.Under 980 nm LD excitation,the Y₂O₃:Ho,Yb ceramic shows strong green upconversion emissions.With the increase of the temperature T,the intensities of 550nm and 665 nm,the intensity ratio I₅₅₀/I₆₆₅ and the relative sensitivity S_R decreased.Moreover,the relationship ln(I₅₅₀/I₆₆₅)=1.22+251.77/T was found and the relative sensitivity S_R was evaluated to be 0.38%/K at 293 K.5.The porous Y₂O₃:Er,Yb ceramics were fabricated by hot-press sintering method using Y₂O₃:Er,Yb nanopowders as raw materials and carbon powder as pore-forming agents.The effect of carbon powder additives on the microstructure,pore size,porosity,and upconversion luminescence were investigated.The temperature-dependent upconversion luminescence spectra were studied and the relative sensitivity was calculated.The results showed that the grain size was 1⁵?m with plenty of closed pores.With the amount of carbon powder from 10wt%to 25wt%,the total porosity increased from 23.89%to 35.81%.With the increase of the temperature,the intensities of 544-566 nm and 646-685 nm and the relative sensitivity S_R decreased,but the intensity ratio I_518-541/I_544-566 almost increased linearly.Moreover,the relationship ln(I_518-541/I_544-566)=1.55-843.67/T was obtained and the relative sensitivity S_R was evaluated to be 1.203%/K at 293 K.