Preparation And Up-conversion Emission Of Er/Tm/Yb Doped Yttria Stabilized Zirconia(YSZ) Single Crystals

Zirconia（Zr O₂）has the advantages of stable physical and chemical properties,high refractive index and low phonon energy(about 470 cm^-1),and is an ideal host material.Since the melting point of yttria-stabilized zirconia（YSZ）is as high as 2700°C,restricts the growth of single crystals,and the optical float zone method can solve this problem well,and it does not need a crucible,which can avoid contamination.Among all rare earth ions,Er³⁺and Tm³⁺have narrow emission lines,rich energy levels,and can realize emission from visible to infrared light,they are common luminescent ions,while Yb³⁺can promote the energy transfer between Er³⁺and Tm³⁺,to improve the luminous efficiency,it was used as a sensitizer in this experiment.By adjusting the concentrations of the three rare earth ions,the Er³⁺-Yb³⁺-Tm³⁺system can achieve a variety of luminescent colors,of which white light is the most widely used,and can be used in laser crystals and displays.In this paper,large-scale（Ф6mm×40mm）high-quality Tm₂O₃,Er₂O₃ and Yb₂O₃ doped yttria-stabilized zirconia（YSZ）single crystals were grown by the optical float zone method,and their microstructure and luminescence properties were characterized.The effect on the luminescence characteristics of the crystal has achieved white light output.The main research contents are as follows:（1）Two series of high-quality single crystals were grown by optical floating zone method.One series was fixed concentration of Er₂O₃（1.50mol%）and Yb₂O₃（2.00mol%）,and the concentration of Tm₂O₃ was changed（denoted as x mol%Tm/Er/Yb:YSZ,where x=0.075,0.100,0.150,0.200,0.250）,the other series is fixed Tm₂O₃concentration（0.50mol%）and Yb₂O₃ concentration（2.00mol%）,change the Er₂O₃ concentration（denoted as x mol%Er/Tm/Yb:YSZ,where x=0.05,0.10,0.20,0.25,0.30）.These crystals have high transparency,no cracks,free of impurities.（2）For x mol%Tm/Er/Yb:YSZ single crystal,there are 11absorption peaks in the range of 230-800 nm,and the optical band gap is in the range of 4.74-4.77e V.The upconversion emission spectra of x mol%Tm/Er/Yb:YSZ crystal samples were excited by a 980 nm laser.It was found that the optimum doping concentration was 0.15mol%,and then the concentration quenching occurred.In the whole process,the luminescence intensity of red and green light produced by Er³⁺decreased monotonously.The blue emission of 0.15mol%Tm/Er/Yb:YSZ crystal increases with the increase of temperature in the range of25-250K,and the thermal quenching occurs after 50K,and the intensity decreases gradually,indicating that temperature has an effect on the luminescence color of the crystal.According to the upconversion power curve test results,red and green emission is a two-photon process,while blue emission is a three-photon process.（3）x mol%Er/Tm/Yb:YSZ series single crystal are cubic phase structure,and when the concentration of Er₂O₃ is 0.05 mol%,Tm₂O₃ is0.50 mol%,Yb₂O₃ is 2.00 mol%,under 980 nm laser excitation,the overall luminous color of crystal is close to white,white output.According to the transmission spectrum,the transmittance of the crystal at this time is up to 80%,good transparency,in the display,fluorescent crystal has important application value.