Effects of MnO₂on the microstructure and electrical properties of 0.94(K_0.5Na_0.5)NbO₃-0.06Ba(Zr_0.05Ti_0.95)O₃lead-free ceramics

Lead-free ceramics MnO2-doped 0.94(K0.5Na0.5)NbO3-0.06Ba(Zr0.05Ti0.95)O3have been fabricated by an ordinary sintering technique and the effects of MnO2on 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)O3ceramics, 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)O3ceramics with 1.00 mol% MnO2doping possess optimum properties: d33= 234 pC/N, kp= 49%, kt= 48%, εr= 1191, tan δ = 1.20% and Tc= 318 °C.