Synthesis and characterization of MnO 2 added (Na 0.475 K 0.475 Li 0.05 )(Nb 0.9 Ta 0.05 Sb 0.05 )O 3 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. MnO 2 was added to NKLNTS ceramics as a sintering aid to improve piezoelectric and dielectric properties. The added MnO 2 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 d 33 -meter and an impedance analyzer. When 0.1 wt% of MnO 2 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 MnO 2 was added, piezoelectric and dielectric properties were decreased due to the decreased density. When NKLNTS-0.1wt% MnO 2 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 d 33 = 271 pC/N, k p = 0.40, ε r = 1250, tan δ = 2.5%, and T c = 348 °C were fabricated.