Study On The Preparation And Properties Of Perovskite-Type Nano-Powders

In the vibrant21st century, innovation of new materials, especially technologies and products based on nanomaterials, will greatly influence society development, economic growth and enhancement of national status. Preparation of inorganic nanomaterials is one of the most important parts in this strategic research field. With this in mind, we selected an important perovskite-type electro-ceramic material, SOx materials, as research objects. Novel synthesis route and controllable strategy of powder properties were studied. Based on these, we prepared three kinds of barium-based perovskite-type nano-powders in RPB, and studied their sintering and dielectric properties after the powders been precalcined.Firstly, nano-sized SOx solid-solution powders have been prepared by low temperature aqueous synthesis method (LTAS) at temperature below100℃and under ambient pressure from cheap starting materials of S2, C2and T4. The as-obtained powders were analyzed by TEM and XRD measurements. It is shown that the as-obtained particles are in form of homogeneous solid solutions when C2+content is lower then80mol%. The morphology of particles is rounded single crystal with somewhat "knobbly" around the edges, and the particle size is decreased from220nm to45nm with the content of the composition S increased.To optimize the performance of the powders, the hydrothermal post-treatment was followed. After the post-treatment, the powders were analyzed by TEM, XRD, FT-IR, TG and ICP measurements. It is shown that the crystal structure of the as-treated powders is orthorhombic phase when the composition is0.1=x=0.4, and it is turned to cubic phase with the content of Sr increased. Compared with the powders prepared by LTAS method, the powders after hydrothermal post-treatment showed much less hydroxyl defects, higher purity, uniform morphology and better crystallinity.Based on the preparation method of SCT, we prepared BZ2, BS2and BSZ2powders in RPB. The as-prepared powders are all single cubic phase perovskite, however, the crystallinity of the powders is inferior and the powders contain the impurity of BaCO3. In order to improve the properties of the particles, the precalcining-treatment was followed. Afer the precalcining, the powders become more pure and better crystallized. The precalcining method improves the shaping and sintering abilities of as-obtained powders. The BZ2, BS2and BSZ2powders precalcined at1000℃show better room temperature dielectric constant of3054,1857and2411, respectively, when unprecalcined powders show room temperature dielectric constant of1582,1008and731. The precalcining procedure could reduce the specific surface area and adsorbing air and water of powders, promote their sintering densification and the dielectric properties.