Fabrication And Properties Of Ytterbium Doped Lutetium Oxide Transparent Ceramics

Solid state laser has been widely used in the field of communication,military,biomedical and metal processing due to its small size,high output power,and excellent performance.Yb:Lu₂O₃ has high theremal conducticity and wide fluorescence emission band,it can be potentially applied as the host material for high-power and ultra-short pulse solid state lasers.The melting point of Lu₂O₃ is about 2500 ^oC,and thus it is quite difficult to fabricate Lu₂O₃single crystals.Compared with single crystals,transparent ceramics are advantageous in many aspects including high doping concentration,possibility of larger size,short preparation period,and high fracture toughness.Therefore,Yb:Lu₂O₃ transparent ceramics have a good application prospect.According to the statement above,we prepared Yb:Lu₂O₃ transparent ceramics by vacuum sintering combined with hot isostatic pressing（HIP）of the powders synthesized by the co-precipitation method.The synthesis parameters of the powder and sintering parameters of ceramic were optimized to obtain highly transparent ceramics Yb:Lu₂O₃.In addition,the spectroscopic properties of Yb:Lu₂O₃ transparent ceramics with different Yb³⁺doping concentration were also studied.The main contents of this thesis are as follows:1)Yb:Lu₂O₃ ceramics were fabricated by the co-precipitation and vacuum sintering method.The samples vacuum sintered at 1850 ^oC for 30h were still opaque because of the serious agglomeration of the powders.Then,we optimized the sintering process and prepared Yb:Lu₂O₃ceramics by vacuum sintering combined with hot isostatic pressing（HIP）treatment.The influence of pre-sintering temperature on the densities,microstructures and optical quality of the Yb:Lu₂O₃ ceramics during vaccum pre-sintering and HIP was studied.The sample pre-sintered at 1500 ^oC for 2 h with HIP post-treating at 1700 ^oC for 8 h has the highest in-line transmittance of 78.2%at 1100 nm and the average grain size of 2.6μm.When the pre-sintering temperature is higher than 1500 ^oC,the transmittance of the samples gradually decreases.2)The effects of calcination temperature on the composition and morphology of the powders were investigated.With the increase of calcination temperature,the content of water,carbonate and sulfate in the powders gradually decreased.Highly pure and well dispersed Yb:Lu₂O₃ nanopowders were obtained by calcining the precursor at 1100 ^oC.However,as the calcination temperature increases to 1200 ^oC,the grain grows up apparently and the agglomeration is aggravated,which was not suitable for sintering.The influence of calcining temperature of powder on the optical quality and microstructures of Yb:Lu₂O₃ ceramics was also studied.It was found that the Yb:Lu₂O₃ ceramic sample sintered from 1100 ^oC-calcined Yb:Lu₂O₃ powders had the highest transmittance.3)The influence of precipitant to metal ions molar ratio（R value）on the properties of Yb:Lu₂O₃ precursors,powders and ceramics was systematically investigated.The results showed that R=4.8 was optimal for the synthesis of Yb:Lu₂O₃ powders and fabrication of Yb:Lu₂O₃ceramics.The in-line transmittace of Yb:Lu₂O₃ ceramics with R=4.8 reached 80%at 1100 nm,which is very close to the theoretical value.4)High transparency Yb:Lu₂O₃ ceramics with different Yb³⁺doping concentration were fabricated and their spectral properties were studied.The absorption coefficients and intensity of emission peaks increased with the rise of Yb³⁺content.The absorption cross-sections of the5at%Yb:Lu₂O₃ ceramic at 947 and 976 nm were calculated to be 0.62×10^-20 and 1.02×10^-2020 cm²,respectively.The emission cross sections of the Yb:Lu₂O₃ ceramic at 1033 and 1080 nm were calculated to be 0.84×10^-2020 and 0.21×10^-2020 cm²,respectively.In addition,5at%Yb:Lu₂O₃transparent ceramics have a wide emission bandwidth,and the half width of emission peaks at1033 and 1088 nm are about 9.2 and 11.4 nm,respectively.These results indicate that the prepared Yb:Lu₂O₃ transparent ceramic is a promising candidate for the high-power solid-state laser.