Study of the synthetic process of CaBi_2Ta_2O_9 powder by the molten-salt method

摘要

The molten-salt method was used to synthesize CaBi_2Ta_20_9 (CBTa) powder, and the influence of temperature on the structure and micromorphology of products was investigated using X-ray diffraction and the scanning and transmission electron microscope. The results showed that highly crystalline CBTa nanoplates exhibit single orthorhombic symmetry and could be obtained in the temperature range of 850-900 °C. Among which, the nanoplates prepared at 900 °C have optimal properties (average grain size of 1.7 μm and uniform size distribution). Above 900 °C, various CaO-Ta_2O_5 binary compounds, Bi_2O_3, and BiTaO_4 formed due to the decomposition of CBTa and subsequent reactions of decomposition products, transforming plate-like grains to cuboid nano-particles with a small amount of prismatic grains. Possible reaction mechanisms at different synthesizing temperature were proposed. This work provides a method for the preparation of template grains to synthesize textured CaBi_2Ta_2O_9 high-temperature piezoelectric ceramics by the template grain growth method.