In this study, supercritical hydrothermal synthesis of BaZrO3 and its formation mechanism during the synthesis were studied using a continuous flow reactor. The Mono-phase, nano-sized BaZrO3 was successfully synthesized at a temperature of 400°C and a pressure of 30 MPa using oxy-zirconium nitrate and excess barium hydroxide as the starting materials. The formation mechanism of BaZrO3 was studied by examining the time dependence of size and composition using XRD, TEM, and ICP. As a result of the time-resolved experiment, the following formation mechanism was revealed. At the first stage of the reaction (∼0.1 s), a perovskite structure forms though it has many defects of Ba site. The particle size increases to 20 nm range by coalescence at the middle stage (∼1 s) and becomes constant at the last stage (1-10 s). Ba site defects are filled by the uptake of Ba with increasing time until the last stage (∼10 s). The elucidated formation mechanism, i.e., the coalescence of nuclei and uptake of Ba, is significant to develop a new methodology for controlling the size and composition of the BaZrO3 nanoparticles.
ASJC Scopus subject areas
- 化学 (全般)