Microwave-Based Fast and Efficient Synthesis of K0.5Na0.5NbO3 (KNN) Ceramics and Its Performance Evaluation

Abstract

K_0.5Na_0.5NbO₃ (KNN) as a lead-free compound has attracted much attention because of its extraordinary response, especially in the MPB regime. However, they are very sensitive to material processing, resulting in variations in the material performance. Processing techniques and conditions must be established to achieve high-density homogeneous ceramics with high piezoelectric performance and determine the compound’s usefulness. In this context, our focus is directed toward comprehending the influence of diverse preparation technologies on the properties of K_0.5Na_0.5NbO₃ (KNN) materials. The KNN ceramics were prepared using the microwave synthesis (MW) route with two different sintering times (30 and 40 min) and solid state (SS) for comparison. From the X-ray diffraction peak, the crystal symmetry of all samples is confirmed as orthorhombic. The KNN 40 min MW (KNN 40 min) sample has the highest dielectric constant, i.e., 3854 °C, with the lowest transition temperature of 425 °C. AC conductivity increases with grain size. The Nyquist plot analysis confirms the significant impact of both the grain and grain boundary on the electrical properties of the compounds. The PE hysteresis loops confirm the ferroelectric character present in all of the KNN samples. The piezoelectric constants are 105 122, and 168 pC/N, respectively, for KNN SS, KNN 30 min, and KNN 40 min samples. The figure of merit value peaked at 10.45 pm²/N for the KNN 40 min MW sample. This sample exhibited the highest output voltage, measuring 13.54 V, and a power density of 20.80 μW/cm².