Influence of synthesis methods on structural, piezoelectric, ferroelectric and mechanical properties of lead-free K0.5Na0.5NbO3 (KNN) ceramics

Abstract

In this work lead free perovskite ferroelectric ceramics, K0.5Na0.5NbO3 (KNN), has been synthesized by two different methods, conventional solid state (SS) and co-precipitation (CPP), from the same starting materials, Nb2O5, Na2CO3 and K2CO3 and their properties have been compared. Double calcination, 700 °C for 7h followed by 850 °C for 6h, of the co-precipitation precursor resulted in single phase perovskite structure (JCPDS card No. 01-077-0038), whereas for solid state precursor a triple calcination, 850 °C for 5h, 1000 °C for 5h followed by 1050 °C for 5h, ended up with producing the cubic perovskite KNN phase. Both samples were sintered at 1120 °C for 2h under atmospheric condition in a muffle furnace. FESEM is used to find the microstructural features. Energy dispersive X-ray spectroscopy is used to confirm the chemical composition of the samples. Evolution of the phase structure and variation in Curie temperature, dielectric constant, piezoelectric voltage coefficient (g33), piezoelectric charge coefficient (d33) as well as mechanical properties such as hardness, stiffnesshave been studied and compared for the KNN samples prepared by two different synthesis methods.