Synthesis of CaCu3Ti4O12 Micron-cubes and rods via high proportion molten salt method

Abstract

CaCu3Ti4O12 (CCTO) particles were produced from a CuO–CaCO3–TiO2 peroxo-hydroxide precursor material in NaCl–KCl and Na2SO4–K2SO4 salt mixtures via the molten-salt synthesis method at different salt-to-precursor mass ratios. Regular-shaped CCTO particles of cubes, rods, and polyhedrons can be obtained at large salt-to-precursor mass ratios of above 50:1. With the extension of sintering time, the particle shape is more regular and the size is larger. Long micro rods with a length of about 53 μm can be obtained at a mass ratio of 125:1 and a long sintering time of 72 h in sulfate salts. The formation mechanisms are also discussed and the results suggest that a large salt-to-precursor mass ratio may provide a sufficient number of Na − K ions to sufficiently modify the particle shape and form regular-shaped cubes and rod-like particles. At the same time, CCTO ceramics synthesized by Na2SO4–K2SO4 molten-salt method show good dielectric properties, with a dielectric constant higher than 104 and a loss factor less than 0.45 in the range of 20 Hz to 1 MHz.