Effects Of Adding Eu³⁺, La³⁺ On The Structures And Properties Of Alumina Ceramics

Alumina ceramic has a lot of excellent performance and it's the most representative engineering ceramic material of extensive use. In order to further improve and enhance the microstructure and the various performance of alumina ceramic, dope in alumina ceramic materials is one of the most effective measures. In this research, the main raw material was the micron class alumina powder which is commonly used in industry and doped with rare earth oxides La₂O₃ and Eu₂O₃. The research adopted the dry-pressed molding method, sintered and prepared alumina ceramic materials in air environment. This research used SEM, XRD, volume density, micro-hardness, bending and compression strength testing methods, etc. And the research mainly studied the effect of agglutinating property, microstructure and the mechanical properties as volume density, micro-hardness, bending strength, compression strength of alumina ceramics by doping La₂O₃, Eu₂O₃ in alumina ceramic materials. This research discussed the laws of alumina ceramic sintered compacts'properties with the change of particle size, sintering temperature and additive level. The research also analyzed alumina samples'microstructure and sintering mechanism, etc.The study concluded that rare earth oxides La₂O₃ and Eu₂O₃ basically consisted in the grain boundaries of alumina ceramics. It could refine the grain, improve the microscopic structure and purify the interface, reduce the transfer speed of Al₂O₃ grain boundary, obviously inhibit the growth of grain and form a compact microstructure. A small amount of La₂O₃ solid solved into the alumina grains in addition to a majority of La₂O₃ distributing at the grain boundaries. It increased the distortion degree of alumina crystal lattice and imperfection, significantly enhanced the activity of particle and thereby promoted the sintering. The fracture path of alumina ceramics doped with La₂O₃ and Eu₂O₃ twisted. The cracking showed the phenomena such as bridging, bending and bifurcating, etc. The fracture energy was improved. Therefore the mechanical properties of alumina ceramic materials were greatly enhanced. When the sintering temperature was 1600℃and holding time was 1h, the bending strength of alumina ceramic doped with 1% La₂O₃ was 443.6MPa, which was better than solely adding Eu₂O₃. The bending strength of alumina ceramic doped with composite rare earth oxides reached 451.3MPa and was the highest. When the sintering temperature was 1580℃and holding time was 1h, the volume density of alumina ceramic compositely doped with 0.75% La₂O₃ and 0.75% Eu₂O₃ was the highest and reached 3.95g/cm³. Alumina ceramics which were prepared by raw material of smaller original particle size had small grains and more grain boundaries. The filling of small grains to each inter-granular pore was better. And the performance of materials was also more stable.