Hydrothermal synthesis of barium zirconate spherical particles with controllable morphology and size

Barium zirconate powders are synthesized via a hydrothermal reaction using a mixture of barium hydroxide and zirconium oxychloride. Three reaction times (3 h, 6 h, and 12 h) and five NaOH concentrations (0 mol/L, 0.5 mol/L, 1.0 mol/L, 2.0 mol/L, and 3.0 mol/L) are used to obtain crystal particles with controllable morphologies and sizes. X-ray diffraction and scanning electron microscopy analyses show that prolonged reaction times promote the phase formation of barium zirconate and improve the crystallinity of the particles. The addition of NaOH to a solvent provides an alkaline environment is necessary to ensure the successful synthesis of barium zirconate. By increasing the NaOH concentration from 0.5 mol/L to 3.0 mol/L, the morphology of barium zirconate particles gradually transforms from an initial irregular shape to a polyhedral shape and subsequently to a spherical shape. The mean particle size decreases from 2.67 μm to 0.64 μm at a reaction time of 12 h, and the size distribution narrows gradually. Moreover, these particles exhibit optimal dispersibility at NaOH concentration of 2.0 mol/L.