Abstract: In order to solve the problem of low sintering density caused by low sintering activity of LiNbO3 powders and loss on ignition of Li element at high temperature, LiNbO3 powders with stoichiometric ratio were synthesized by solid phase reaction method. The oxygen vacancy concentration of LiNbO3 powders increased by reduction treatment, and then high density LiNbO3 ceramics were prepared by spark plasma sintering (SPS) technology. The phase composition, oxygen vacancy concentration and surface morphology of LiNbO3 powders and the sintered body were characterized and analyzed by XRD, EPR, XPS, Raman spectroscopy and SEM. The results show that the oxygen vacancy concentration of LiNbO3 powders increases significantly after 700 ℃ reduction treatment, and the oxygen vacancies generate at the lattice position of O atom in Nb—O octahedron. With the increase of SPS temperature, the relative density of LiNbO3 ceramics shows a trend of increasing first and then decreasing. The relative density of sintered body reaches a maximum of 98.19% at 900 ℃. After annealing and oxygen increasing treatment at 800 ℃, the color of LiNbO3 ceramics changes from black to white. At the same time, the oxygen vacancy defect of LiNbO3 ceramics is eliminated and the relative density is 98.32%. This study provides a new idea for the preparation of high density alkali metal niobate ceramics.
Key words: LiNbO3, oxygen vacancy, Nb—O octahedron, spark plasma sintering, relative density, grain size
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