The "top-down" process via direct conversion of the micro (mu m)-to-submicroscale (sub-mu m) particle was applied in this work by using eutectic chloride salts to prepare BaZrO3. The particle size at optimum condition could be decreased by more than 10 times from 2.1 +/- 0.9 mu m to 168 +/- 23 nm without destroying the 1:1 of Ba:Zr stoichiometry. The uniform sub-mu m-BaZrO3 powder was sintered in order to obtain similar to 98% dense ceramic at 1400 degrees C/10 h, which is significantly lower than the 1650 degrees C in normal cases. The microwave dielectric constant, tan delta, and quality factor were also determined. Furthermore, this method also was applied to lead-free piezoelectric material in the 0.87BaTiO(3)-0.13BaZrO(3)-CaTiO3 (0.87BT-0.13BZ-CT) system. The particle size of 0.87BT-0.13BZ-CT was reduced greatly from >10 mu m to 2.8 +/- 0.4 mu m. It can be proved that salt flux dissolution method enables high-purity with uniform sub-micro/nanometer powder production in one step by using simple laboratory equipment and low-cost raw materials.