Lead-free (Ba_0.7Ca_0.3)TiO₃-Ba(Zr_0.2Ti_0.8)O₃-xwt %CuO ceramics with high piezoelectric coefficient by low-temperature sintering

Lead-free (Ba_0.7Ca_0.3)TiO₃-Ba(Zr_0.2Ti_0.8)O₃-xwt %CuO(BCZT-xCu) piezoelectric ceramics have been fabricated by the solid-state reaction process and the effects of CuO addition on the phase structure and piezoelectric properties of the ceramics have been studied. Our results reveal that the addition of CuO significantly improves the sinterability of BCZT ceramics which results in a reduction of sintering temperature from 1,540 to 1,350 °C without sacrificing the high piezoelectric properties. X-ray diffraction (XRD) data shows that CuO diffuses into the lattice of BCZT-xCu ceramics and a pure perovskite phase forms in the ceramic. SEM images indicate that a small amount of CuO addition affects the microstructure, obviously. Main piezoelectric parameters of these ceramics are optimized around x = 0.04 wt % with a high piezoelectric coefficient (d ₃₃ = 510 pC/N), a planar electromechanical coefficient k _p of 45%, a high dielectric constant (ε _r  = 3,762) and a low dissipation factor (tanδ = 1.05%) at 1 kHz. The results indicate that the BCZT-xCu ceramics are promising lead-free practical applications.