Study the Structural, Electrical and Ferroelectric behaviour of Lead-Free Sodium Potassium Niobate (KNN) Ceramics in View of Energy Storage Capacity

This study presents the synthesis of KNN ceramic structural, dielectric, impedance, and energy storage behavior using the solid-state reaction method. Preliminary structural studies were conducted using X-ray diffraction and Raman spectroscopy at room temperature. The results indicate that KNN exhibits orthorhombic symmetry based on the XRD and Raman data obtained at room temperature. The SEM analysis of the KNN powder showed that the material had undergone densification and that the grain size was comparable. Two phase transitions were observed in the dielectric graph: from orthorhombic to tetragonal at T_O−T (~ 220 °C) and from tetragonal to cubic at T_T−C (~ 440 ºC) for frequencies of 100 kHz, 500 kHz, and 1 MHz. As the frequency increases, the net polarization of the material decreases, resulting in a decrease in the values of ϵ and tanδ. The internal vibrations of the NbO₆ octahedron, specifically at 256.65 cm^− 1, 439.21 cm^− 1, 612.48 cm^− 1, and 871.98 cm^− 1, are correlated with the structure and ferroelectric properties of KNN materials. The temperature data and frequency dependence of the impedance were used to analyze the sample’s electrical conduction, revealing a negative temperature coefficient resistance (NTCR). The promising outcomes demonstrate that KNN based lead free ceramics composition is potential material for energy storage and various sensor-based applications.