Effects of MnO2 on the microstructure and electrical properties of 0.94(K0.5Na0.5)NbO3-0.06Ba(Zr0.05Ti0.95)O3 lead-free ceramics

Lead-free ceramics MnO2-doped 0.94(K0.5Na0.5)NbO3-0.06Ba(Zr0.05Ti0.95)O-3 have been fabricated by an ordinary sintering technique and the effects of MnO2 on the microstructure and electrical properties of the ceramics have been studied. Our results reveal that a small amount of MnO2 (0.50-1.00 mol%) can improve effectively the densification and electrical insulation of the ceramics. For 1 mol% MnO2-doped 0.94(K0.5Na0.5)NbO3-0.06Ba(Zr0.05Ti0.95)O-3 ceramics, the ferroelectric tetragonal-ferroelectric orthorhombic phase transition (TO-T) resides near room temperature, indicating the coexistence of the orthorhombic and tetragonal phases at room temperature. Because of high densification, good electrical insulation, the donor- and acceptor-doping effects of MnO2, and the coexistence of the orthorhombic and tetragonal phases, the piezoelectric and dielectric properties of the ceramics are improved considerably. The 0.94(K0.5Na0.5)NbO3-0.06Ba(Zr0.05Ti0.95)O-3 ceramics with 1.00 mol% MnO2 doping possess optimum properties: d(33) =234 pC/N, k(p) = 49%, k(t) = 48%, epsilon(r) = 1191, tan delta = 1.20% and T-c =318 degrees C. (C) 2007 Elsevier B.V. All rights reserved.