Microstructure, dielectric and piezoelectric properties of (K0.5Na0.5)NbO3-Ba(Ti0.95Zr0.05)O3 lead-free ceramics with CuO sintering aid

Using an ordinary ceramic fabrication technique, we fabricated lead-free (1- x)(K0.5Na0.5) NbO3-xBa(Ti-0.95 Zr-0.05) O-3 ceramics with CuO sintering aid. Ba(Ti0.95Zr0.05) O-3 diffuses into (K0.5Na0.5) NbO3 to form a new solid solution. The ceramics with perovskite structure possess orthorhombic phase at x <= 0.04 and become tetragonal phase at x >= 0.06. Both the paraelectric cubic - ferroelectric tetragonal and the ferroelectric tetragonal - ferroelectric orthorhombic phase transition temperatures decrease with increasing the concentration of Ba(Ti0.95Zr0.05) O-3. The doping of CuO effectively promotes the densification of the ceramics. The coexistence of the orthorhombic and tetragonal phases at 0.04 < x < 0.06 and the improvement in sintering performances of the ceramics significantly enhance the piezoelectric and dielectric properties at room temperature. The ceramics with x = 0.04 0.06 and y = 0.75 - 1.50 possess excellent properties: d(33) = 119 - 185 pC/N, kP = 37% - 44%, kt = 35% - 49%, epsilon = 341 - 1129, tan delta = 0.7% - 4.4% and T-c = 312 - 346 degrees C.