Fabrication And Properties Of Yttrium Oxide-based Transparent Optical Functional Ceramics

The 21st century is the era of information economy,which is the era of great integration of science and technology with photon computer as the beginning and light as the medium.Under the background of this era,the application of light and the development of optical-functional material are particularly important.As a new favorite in the field of modern optical-functional materials,transparent ceramics will find more and more applications in many fields,including industry,military,exploration,medical,etc.Yttrium oxide transparent ceramics with cubic structure have received extensive attention in the field of optical-functional material due to their excellent physical and chemical properties.Pure Y₂O₃ transparent ceramics are considered as brilliant high-temperature windows and infrared dome materials due to their wide optical transmittance and low infrared spontaneous emissivity.Y₂O₃ transparent ceramics doped with rare earth ions are considered to have great application prospects in femtosecond lasers and irradiation detection materials due to their advantages such as high absorption efficiency,high thermal conductivity,low phonon energy and strong irradiation resistance.Based on the above background,the preparations and performances of Y₂O₃ and RE?Yb or Eu?:Y₂O₃ transparent ceramics were studied and optimized.Nano-RE:Y₂O₃ powders with high dispersion and high sinter-ability were successfully synthesized by co-precipitation method,and then high optical quality Y₂O₃ based transparent ceramics were prepared by vacuum sintering combined with hot isostatic pressing?HIP?treatment.The spectral properties of yttrium oxide transparent ceramics doped with different rare earth ions were also studied.The main contents of the thesis are as follows:1.Y₂O₃ nanopowders were prepared by precipitation method.The influences of calcination temperature on the particle size,morphology and agglomeration of Y₂O₃ nanopowders were preliminarily investigated.The Y₂O₃ transparent ceramics were successfully fabricated by vacuum pre-sintering combined with HIP post-treatment from the powders calcined at 1100^oC.The influences of pre-sintering temperature on the density,microstructure and optical quality of Y₂O₃ ceramics before and after HIP treatment were studied.The sample pre-sintered at 1500^oC for 2 h with HIP post-treating at 1550^oC for 3 h had the highest in-line transmittance.The mechanical properties of Y₂O₃ ceramics were also studied.2.5at.%Yb:Y₂O₃ nanopowders were prepared by co-precipitation method.The influences of R value?molar ratio of ammonium hydrogen carbonate to metal ions?on the properties of Yb:Y₂O₃precursors,calcined powders and ceramics were investigated.The nanopowders with R=4.0showed weak agglomeration.With the increase of R value,the transmittance of ceramics increased firstly and then decreased,in which the Yb:Y₂O₃ ceramics with R=4.0 had the highest transmittance.In the case of selecting R value of 4.0,the influences of calcination temperature on the composition and morphology of the powders were investigated.The results showed that the Yb:Y₂O₃ powders calcined at different temperatures were pure Y₂O₃ phase.The Yb:Y₂O₃powders calcined at low temperature showed weak agglomeration,while the powders calcined at a high temperature tended to form sintering necks,which would make agglomeration more serious and was not conducive to fabricating ceramics.The powders calcined at 1150^oC had good dispersion and sintering activity,and the sintered ceramics had the highest optical transmittance.3.The influences of sintering temperature?vacuum pre-sintering temperature and HIP post-treatment temperature?on microstructure and optical quality of 5at.%Yb:Y₂O₃ ceramics were studied.It was found that the optimal vacuum pre-sintering temperature and HIP post-treatment temperature were 1450^oC and 1550^oC,respectively.The obtained ceramics had the highest in-line transmittance of 81.4%at the 1100 nm,which was close to the theoretical transmittance.4.The absorption cross section,emission cross section and gain cross section of the5at.%Yb:Y₂O₃ ceramics were calculated.The prepared 5at.%Yb:Y₂O₃ transparent ceramics have a wide absorption and emission band,which are considered to be a promising gain medium for ultrashort pulse lasers.5.4at.%Eu:Y₂O₃ scintillation ceramics were prepared by solid-phase ball milling and co-precipitation,respectively.The Eu:Y₂O₃ ceramics were poor in optical quality due to the agglomeration of the initial ball milling powders,while the Eu:Y₂O₃ ceramics had a higher optical transmittance from highly dispersive co-precipitated powders.The 4at.%Eu:Y₂O₃transparent ceramics prepared by the co-precipitation method have high optical output and are considered as a very promising scintillating material.