Direct observation of intermediate twinning in the phase transformations of ferroelectric potassium sodium niobate

In this study, temperature-dependent X-ray diffraction and transmission electron microscopy have been combined to reveal the mechanisms in the first-order phase transitions of ferroelectric K0.5Na0.5NbO3. Hereby, abnormal grain growth has been suppressed in the bulk material since it is a feature known to inhibit measurement reproducibility due to the introduced inhomogeneities. It is shown that phase transitions in this ceramic are multi-step processes, which feature an intermediate twinning stage. As perovskite-type ceramics can be regarded as model systems with respect to displacive transformations, the presented experiments give an insight into nucleation, propagation path and twinning mechanisms in ceramic materials.

Automated summary

Temperature-dependent X-ray diffraction and transmission electron microscopy were used in this study to investigate the first-order phase transitions of ferroelectric K0.5Na0.5NbO3. The results revealed that the phase transitions in this ceramic are multi-step processes, featuring an intermediate twinning stage. Perovskite-type ceramics can be considered as model systems for displacive transformations, and the experiments presented here provide insight into nucleation, propagation path, and twinning mechanisms in ceramic materials.