Synthesis and characterization of MnO2 added (Na0.475K0.475Li0.05)(Nb0.9Ta0.05Sb0.05)O3 lead-free piezoelectric ceramics

Lead-free NKLNTS ceramics with promising piezoelectric properties were fabricated using the solid phase method, which is a general ceramic manufacturing method. MnO2 was added to NKLNTS ceramics as a sintering aid to improve piezoelectric and dielectric properties. The added MnO2 content was adjusted to 0, 0.1, 0.3, 0.5, and 0.7 wt%, the powder was calcined at 900 °C for 2 h, and then the sintering temperature was changed from 1000 to 1100 °C to study the optimum temperature and composition that yields excellent piezoelectric properties and sinterability. Archimedes method and scanning electron microscope (SEM) were used to evaluate the sinterability, X-ray diffraction analysis (XRD) was performed to confirm the crystallinity of the sintered body, and piezoelectric and dielectric properties were evaluated using a d33-meter and an impedance analyzer. When 0.1 wt% of MnO2 was added, it was confirmed that density was the highest at the sintering temperature of 1050 °C and had excellent piezoelectric and dielectric properties. When 0.3 wt% or more of MnO2 was added, piezoelectric and dielectric properties were decreased due to the decreased density. When NKLNTS-0.1wt% MnO2 was sintered at a sintering temperature of 1050 ℃ for 2 h, it had a density of about 97%. Furthermore, lead-free piezoelectric ceramics with excellent piezoelectric and dielectric properties of d33 = 271 pC/N, kp = 0.40, εr = 1250, tan δ = 2.5%, and Tc = 348 °C were fabricated.