Hydrothermal Synthesis Of Rare Earth Doping Of Batio <sub> 3 </ Sub> Powder Preparation

BaTiO₃ electronic ceramics is the basic material of dielectric and semiconductor ceramics, which was widely used in martial and demotic electronic machine. As the grain size of BaTiO₃ powder which is synthesised by solid-state reaction is too big to satisfy the request in the precision component. So it is the research emphases and hotspot that adopting advanced techniques to prepare fine BaTiO₃ powder.To begin with, BaTiO₃ nanoparticle was synthesized by hydrothermal method, using BaCl2·2H2O, TiCl4 as the raw materials and NaOH as mineralizes in this paper. The composition, morphology, microstructure of BaTiO₃ powders were investigated by XRD, SEM and TG–DTA analysis. The effect of Ba/Ti molar ratio, the excess concentration of NaOH aqueous, the reaction time and temperature were studied. As is indicated by results: The pure tetragonal barium titanate powder was obtained at 230oC, in only 12h under the conditions of Ba/Ti =1.6, the NaOH excess concentration was 1.5mol/L.Furthermore, Dy doped barium titanate or La doped barium titanate powder was prepared by the hydrothermal reactions. As depicted in resulting: (1) Dy or La entered into the BaTiO₃ lattice in the range of the experiment doped contents(W(Ln2O3)%: 0.2～1.2). There's no second phase appeared in the BaTiO₃. Ba site was replaced if a little Dy2O3 was doped but some more Dy would take up the positions of Ti. Majority of La3+ entered the crystal lattice to substitute of Ba2+, as they had the closely radius;(2) When Dy2O3 content was 0.6wt%, grains growth was effectively restrained and ceramic grain size was 400nm, the dielectric constant getted up to 4700 in the room temperature. And When La2O3 content was 0.8wt%, the crystal constant getted the maximum, the dielectric constant achieved 4879.Finally, the ceramic preparation craft was studied and the influence factors in the processes of pelleting, tabletting, ejecting glue, sintering, drive silver and the metallization were discussed. Our lab have also established the reasonable technological conditions which enabled the prepared ceramic to achieve the anticipated B4–402 performance(εr: 2400～2800; tgδ≤1.5×10-2).