Preparation And Optical Properties Of Rare-Earth Doped Alpha-Sialon Transparent Ceramics

α-sialon ceramics doped with various rare-earth were prepared by hot-pressing sintering. Phase components and microstructure were analysized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Optical transmissions properties in wave number of 200-5000 were studied. The effects of rare earth and the sialon composition on the transmittance were also analysized. The fluorescence property and luminescence methanism in the Eu1010E2 material was discussed.The experimental results indicated all the samples reached full densification by hot-pressing at 1900℃for 60 min under 25MPa uniaxial pressure. The phase components changed with the rare earth dopants in the sialons which have the same composition as Re0.33Si10Al2ON15. Pureα-sialon were obtained in the YbNd, and YbY doped compositions while sameβ-sialon phase together with a small amount of other crystalline phases was detected in the Nd, Eu, and LuSc sialons. Futhermore, AlN polytypoid were also observed in the LuSc and Eu sialons. The phase assemblages changed systematically with compositions in the Y-sialon system. The boundary line composition yielded pureα-sialon, on the contrary both Y1510E2 and Y1515E2 had some M'.β-sialon phase were also detected in the Y1515E2 material.Experimental results showed that all the ceramics had optical transmission to some degree in the wavelength rang from 200-5000nm. YbNd and YbY sialons had high transmittance up to 73.46% and 73.19% respectively while LuSc sialon could only get maximum transmittance of 20.21%. Study in the Y-sialon system indicated that the Y1510E2 sialon with high N and low O concentration had better transmittance than the Y1015E2 sialon with low N and high O concentration. Microstructure observation by SEM and TEM showed that phase components, grains morphologies, and component of the secondary phases had significant effects on the mechanical and optical properties.The luminescent test indicateded the existence of only one wide emit peak around 509nm in Eu1010E2 material. The Eu3+ trapped in theα-sialon lattice could not show luminescence effect. A large amout of Eu2+ in theβ-sialon and S phase which was reduced from during hot-pressing exhibited luminesce corresponding to the 5d→4f electron transition when they were exited by laser light.