Research On Preparation And Optical Properties Of Yttrium Oxide Transparent Ceramics

Transparent ceramics with high optical quality are widely used in laser,military and medical fields.Yttrium oxide transparent ceramic has attracted much attention due to its excellent physical and chemical properties.Due to the fact that the precipitation method is simple and low cost,and its synthesized powders possessed high activity,the precipitation method has been usually used to prepare yttrium oxide transparent ceramics.However,it is difficult to guarantee the dispersion of powders and the optical quality of ceramics by using precipitation method.Therefore,it is necessary to deeply analyze the internal mechanism of the phase of powder synthesis and ceramic sintering in the process of preparing transparent ceramics by precipitation method,and to optimize some key parameters.The main research work of this paper is as follows:Firstly,the preparation method of precursor and yttrium oxide powder precipitation based on 4-pitched-blade turbine impeller stirring was proposed.The influences of impeller shapes on homogeneity of solution reaction,morphology of precursor,dispersion and sintering activity of yttrium oxide powder during precipitation were studied for the first time.The results of ANSYS analysis showed that the flow pattern of reaction solution was axial flow when used the4-pitched-blade turbine impeller.The cycling and shearing effects were obviously better than those of other types of agitators,and the dispersion and particle size uniformity of precursors and powders were greatly improved.The prepared yttrium oxide powder had the particle size of142.8nm,uniform particle size distribution and good sintering activity.Secondly,the intrinsic mechanism of yellowing in sintered yttrium oxide transparent ceramics was studied.It was found that due to the introduction of a lot of?NH₄?₂SO₄ dispersant in the early stage of the precipitation process,a large amount of sulfur impurities remained in the ceramics and eventually resulted in the yellowing of the ceramics.On this basis,the proportion of dispersant were optimized.By reducing the content of?NH₄?₂SO₄ and introducing moderate PEG4000,the electrostatic repulsion of?NH₄?₂SO₄ was combined with the steric hindrance of PEG4000 long molecular chain.Thus,the dispersion of yttrium oxide powder was improved and the yellowing phenomenon of yttrium oxide ceramics was solved.Then,in order to solve the problem of low transmittance of yttrium oxide transparent ceramics after sintering,the densification behavior of ceramics during sintering stage was regulated by optimizing the content of sintering aids.By doping 3.0 at.%Zr⁴⁺ions,the densification rate of yttrium oxide ceramics was effectively controlled,pores inside the ceramics were basically eliminated,and the optical quality of the ceramics was greatly improved.The transmittance of yttrium oxide ceramics?sample thickness is 1mm?at 800nm reached 80.1%,and the transmittance after 1000nm was more than 82%,which was very close to the theoretical transmittance of yttrium oxide.Finally,in order to further explore the functional application of yttrium oxide ceramics on laser,7.0 at.%Er:Y₂O₃ transparent ceramics were prepared by doping a certain amount of Er³⁺into the ceramics.The absorption coefficient of the samples reached 6.0cm^-1,the transmittance at2700nm was higher than 82%,and the scattering points were less,which possessed the excellent optical quality.