Abstract
This work presents the suppression of abnormal grain growth in bulk ceramic K0.5Na0.5NbO3 (KNN). The suppression is enabled by precise control of the starting powder morphology through match of milling and calcination duration. A comparative temperature-dependent analysis of the resulting sample morphology, phase transitions and related electronic material properties reveals that abnormal grain growth is indeed a major influence in material property deterioration, as has theoretically been suggested in other works. However, it is shown that this abnormal grain growth originates from the calcined powder and not from sintering and that all subsequent steps mirror the initial powder morphology. In specific, the results are discussed with respect to the predictions of the compatibility theory and microstructure. Despite the material’s multi-scale heterogeneity, the suppression of abnormal grain growth allows for the achievement of significantly improved functional properties and it is reported that this development is correctly predicted by the compatibility theory within the borders of microstructural integrity. It could be demonstrated that functional fatigue is strongly minimised, while thermal and electronic properties are improved when abnormal grain growth is suppressed by powder morphology control.
Highlights
This work presents the suppression of abnormal grain growth in bulk ceramic K0.5Na0.5NbO3 (KNN)
The procedure needs to be repeated for that the process of abnormal grain growth is self-accelerating
On the basis of the dynamic light scattering (DLS) and SEM analysis it could be demonstrated that this successful suppression of abnormal grain growth is the reason for a dramatic improvement of material performance in terms of microstructure homogeneity and that it can be achieved by controlling the powder morphology solely
Summary
This work presents the suppression of abnormal grain growth in bulk ceramic K0.5Na0.5NbO3 (KNN). It is known that the starting materials have a crucial effect on the resulting bulk morphology the influence of fluctuations in calcined KNN powder has often been analysed separately[21] or has even been neglected, as the origin of insufficient material performance has been attributed to the multi-scale heterogeneity occurring during sintering. Notwithstanding that chemical heterogeneities are often tolerated and incorporated into the analyses in a descriptive way, their control is of special importance as alkali deficiency is a frequently reported problem in KNN processing Taking all of this into account, the fabrication of high quality potassium sodium niobate remains a major challenge and demands for deeper knowledge and new design rules. This set of rules is widely applied in metal compositions in high-cycle medical applications e.g. nickel titanium based composites[50,51]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
