Influence of Structural Phase Transitions on the Mechanical Behavior of Lead-Free Potassium Sodium Niobate Piezoceramics

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A growing critical environmental issue exists related to the increasing use of toxic lead-based piezoelectric ceramics for various sensor and actuator applications. There have been substantial scientific and industrial efforts towards the development of lead-free alternatives, which have led to the identification of various potential material systems. Polycrystalline (KxNa1- x)NbO3 (KNN) remains one of the most promising candidates, with a high Curie point, stable electromechanical response over a wide usable temperature range, high acoustic vibration velocities, and low density. Despite the numerous advancements in tailoring the electromechanical properties, there has been very little work on understanding the mechanical response, in particular the fracture behavior, which is crucial for reliable commercial implementation. During operation piezoelectric ceramics are often exposed to high operating temperatures and large compressive stress, used to reduce cracking. Therefore, the aim of this project is to use combined and complementary experimental techniques and expertise in Germany and China to characterize the temperature-dependent mechanical properties and in situ stress-dependent crystal structure of KNN with various advanced novel measurement techniques.