超临界水热合成纳米钛酸钡结晶机理研究

To address the challenges of poor particle size controllability, severe agglomeration, and limited tetragonal phase content in the conventional synthesis of BaTiO₃nanoparticles, a continuous flow supercritical hydrothermal synthesis apparatus was employed to elucidate the regulatory effects and mechanisms of reaction temperature on the crystallization behavior of nanoBaTiO₃establish a quantitative relationship between nucleation rate and supercritical supersaturation, and determine the optimal temperature window for obtaining high tetragonal-phase fraction and narrow particle size distribution.The products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy to assess crystal phase composition, crystallinity, and particle size distribution.The results indicated that reaction temperature, by altering the physicochemical properties of supercritical water, significantly affected the crystallinity, grain size, and phase composition of BaTiO₃and dominated the nucleation-growth competition mechanism；an optimal reaction temperature range of 380-400℃ was identified in which high tetragonal-phase content, small grain size, and narrow particle size distribution were achieved. The high supersaturation, low viscosity, and high diffusivity of supercritical water were found to jointly increase the nucleation rate, effectively suppress grain growth, and enable nanoscale particle size control.During the supercritical hydrothermal synthesis, with increasing temperature, the crystallization mode of BaTiO3was observed to shift from homogeneous nucleation toward heterogeneous nucleation, and grain growth was governed by both diffusion and agglomeration kinetics.This study provides new insights for the controllable synthesis of high-performance nano-BaTiO3 and offers guidance for the design of key powder precursors for high-density, high-dielectric electronic ceramics.