Optical Properties Of Alpha-Sialon Ceramics

In this thesisα-sialon ceramics doped with four kinds of rare-earth oxides (Y₂O₃, Dy₂O₃, Yb₂O₃, Lu₂O₃), were prepared by hot-pressing (HP) sintering. The phase analysis was performed using X-ray diffraction (XRD). Microstructure of the samples was observed by scanning electron microscopy (SEM), and characterized in detail by transmission electron microscopy (TEM). The effect of different rare-earth oxides on the mechanical properties and microstructure were studied, the mechanism of ceramic's toughness was discussed. Furthermore, the optical properties ofα-sialon ceramics doped with different rare-earth oxides were researched.The experimental results indicated the full densityα-sialons were successfully synthesized in this work and Y-α-sialon,Dy-α-sialon and Yb-α-sialon ceramics were composed of singleα-sialon phase. But a small amount of secongdary crystalline phases J'(Lu₄Si_2-xAl_xO_7+xN_2-x) were detected in Lu-α-sialon. The results of SEM show that, the elongeted grains were formed in the Y³⁺, Lu³⁺ cations dopedα-sialon. Andα-sialon with the elongeted grains performed the better mechanical properties, especially for Lu-α-sialon, the fracture toughness value of 4.4MPam1/2. The main toughing mechanism was crack deflection and pulling out of equiaxed grains.The analysis of the transmittance showed all theα-sialon ceramics prepared in the thesis performed optical transmission over the wavelength range of 400-3000nm. And the scattering center formed in the microstructure was most important for the optical transmission ofα-sialon ceramics. The maximal optical transmittance was achieved 63.5% in the wavelength of 2636nm for Yb-α-sialon ceramic, due to few boundary phases in the material. The optical trasmission was 50% in the near-infrared region (1000-3000nm) for theα-sialon ceramics doped with Y₂O₃ and Dy₂O₃. The transmittance of the Lu-α-sialon, which had more glass phases in the grain boundary, was lower. However, there was a little of transmission in the ultraviolet band for Lu-α-sialon ceramic.The linear-fit of transmittance was performed in the wavelength of 1500nm, 2000nm, 2500nm via the simplified Lambert-Beer principle for Dy-α-sialon with...