Structure evolution of bismuth ferrite synthesized by hydrothermal route

The Bismuth ferrite (BiFeO₃) powders were hydrothermally synthesized using Fe(NO₃)₃·9H₂O and Bi(NO₃)₃·5H₂O as starting materials, and NaOH as a mineralizer. Phase structure and micro-morphology of BiFeO₃ powders under various reaction conditions were investigated. Results show that only impurity phase is observed at low reaction temperature. With increasing reaction temperature, the impurity phase is reduced and the BiFeO₃ phase is significantly increased. The extension of reaction time could reduce impurity phase, and pure BiFeO₃ is achieved with low mineralizer concentration of 1 mol/L calcined at 170℃ for 24 h. Furthermore, the products with different morphologies are obtained by adjusting reaction condition, such as slices, spheroids, nano-particles, nano-wires, tetrahedrons. It is found that large-scale spheroids (~10 μm) could be obtained with moderate reaction temperature, time and mineralizer concentration, and the increase of reaction time promotes the growth of one-dimension nano-structures and nano-particles.