Control of crystal phase and morphology in hydrothermal synthesis of BiFeO3 crystal

• Reaction temperature and KOH concentration are the keys to grow BiFeO3 crystal phase.
• Growth mechanism of BiFeO3 is closely related to Bi:Fe molar ratio in solution.
• Large BiFeO3 crystal was grown at high KOH concentration and low supersaturation.
• Increasing compactedness will reduce surface defect and improve crystal quality.

Bismuth ferrite crystal is synthesized by hydrothermal method. The effect of hydrothermal temperature, KOH concentration, supersaturation, cooling rate, and compactedness on the crystal phase and the morphology of product were investigated. The results indicated that BiFeO3 microcrystalline with good quality could been synthesized at 140–240 °C with KOH concentration of 4–14 mol L−1. In addition, it is favorable for improving the crystal quality to reduce the supersaturation and decrease the cooling rate. With the increasing of the compactedness, surface holes and cracks of the as-grown crystals would be reduced. The optimization of hydrothermal condition provides guidance to grow BiFeO3 crystal with a large size and high quality for practical application.