Preparation And Characterization Of Rare Earth Oxide Transparent Laser Ceramic Powders

Rare earth oxide transparent ceramics have been paid much attention for excellent physical properties and superior optical characteristics. In comparison with single crystal and glass, the characteristics of rare earth oxide transparent ceramics offer several advantages, such as fabricated in large size easily, produced in mass with lower cost, and obtained higher output due to the high doping concentration. So it becomes a competitive substitute material for single crystal and glass.The powders of (Nd:GdLa)₂O₃ and Er:Gd₂O₃ were prepared by co-precipitation method and sol-gel combustion method, by the comparing these two methods, we concluded that co-precipitation method was better than sol-gel combustion method. Then the co-precipitation method was choosen to prepared the powders of Nd:Y₂O₃ and Nd:YAG with three different precipitants, in comparison, we thought multi-precipitant was the best. The process of heat disassembly, phase composition, morphology and purity of the powders were analyzed by TG-DTA, XRD, SEM and FTIR, respectively.The structure of (Nd:GdLa)₂O₃ powders prepared with complex co-precipitation method was cubic after heat treatment with different temperatures, its grains were slice-like and uniform, having small-size and clear crystal boundary. With the increasing of heat treatment temperature, the structure of (Nd:GdLa)₂O₃ powders prepared by sol-gel combustion method was changed from monoclinic to cubic. With 1100°C heat treatment, (Nd:GdLa)₂O₃ powders prepared by sol-gel combustion were agglomerated, having a fluffy and porous morphology. Then with 1300°C heat treatment, the powders were turned into cubic structure, its grains were spherical and uniform, having large-size and clear crystal boundary. Er:Gd₂O₃ powders having cubic phase were obtained by sol-gel combustion method when citric acid and EDTA were used as combination fuel. cubic phase was better than monoclinic phase to the optical performance of powders in laser respect. But the powders also were fluffy, porous and agglomerated and its grains were irregular in morphology. Besides of oxalate being generated, Gd2O2CO3 was generated in the process of heat treatment by oxalic acid co-precipitation method. The decomposition temperatures of oxalate and Gd2O2CO3 were about 401oC and 642oC. The grains prepared by acid co-precipitation method were in shape of flaky, having uniform size and clear crystal boundary. After 900oC heat treatment, the average length of flaky grains was about 1μm, and the average thickness was about 20nm. The powders prepared by these two methods were easy to absorb CO2 and H2O to form CO32- on the surface of the grains OH-. By general comparison, it could be concluded that co-precipitation method was better than sol-gel combustion method to prepare rare earth oxide transparent laser ceramic powders.In co-precipitation method, the more strict reaction conditions were needed, if the urea was used as the precipitant. Under this strict reaction condition sulphate precipitate could be formed, which was difficultly decomposed in the process of heat treatment. If oxalic acid was used as precipitant, the powders grains prepared by co-precipitation method had large-size and irregular morphology. And Al3+ and Y3+ were difficultly precipitated by oxalate at the same time. By general comparison, it is concluded that multi-precipitant composed of NH4HCO3 and NH3H2O was better than urea and oxalic acid to prepare Nd:Y₂O₃ and Nd:YAG transparent laser ceramic powders. After 3h heat treatment at 1000°C, the powders prepared by multi-precipitant composed of NH4HCO3 and NH3H2O at the ratio of 1:3 had a clear crystal boundary, and its grains were...