High Strain in (K,Na)NbO3‑Based Lead-Free Piezoelectric Fibers

Until now, lead zirconate titanate (PZT)-based ceramics are the most widely used in piezoelectric devices. However, the use of lead is being avoided due to its toxicity and environmental risks. Indeed, the attention has been moved to lead-free ceramics, especially on potassium sodium niobate (KNN)-based materials, due to growing environmental concerns. These materials are technologically interesting. For applications such as actuators, an electromechanical coupling providing high strain with high force, e.g, fuel injection, ultrasonic motor, etc., is required, Moreover, in the current context, the new technologies evolve toward the miniaturization of the conventional electronic devices. Herein, we have developed microfiber ceramics of KNN-based composition, which yield a high strain value with S max as high as 0.17% at 3 kV mm–1. According to our results, this phenomenon can be explained by an extrinsic effect that favors the internal relaxation of the system. To reach this breakthrough, a sintering mechanism has been established, which allows for correlating the extrinsic factors of the system with electromechanical properties of the ceramic fibers. We believe that the general strategy and design principles described in this study will open new avenues in developing of (K,Na)­NbO3-based lead-free piezoelectric fibers with enhanced properties for high-precision sensor and actuator applications.