Phase structures and electrical properties of (1-x)(K0.48Na0.52) NbO3-x(Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 lead-free ceramics

Lead-free ceramics (1-x)(K0.48Na0.52)NbO3-x(Ba0.85CaO0.15)(Zr0.1Ti0.9)O-3 doped with 1.0 mol% MnO2 were prepared using a solid-state reaction technique. The phase transition behavior and electrical properties of the ceramics were studied. Results show that (Ba0.85CaO0.15)(Zr0.1Ti0.9)O-3 diffuses into (K0.48Na0.52)NbO3 to form a new solid solution, and induces a phase structure transition from orthorhombic to tetragonal phase with the increase of x. At 0.04 <= x <= 0.06, coexistence of the orthorhombic and tetragonal phases is observed, and enhanced piezoelectric properties are achieved in this region due to the polymorphic phase transition near room temperature. The doping of MnO2 effectively promotes the densification of the ceramics and further enhances the piezoelectric and dielectric properties at room temperature. The ceramics with 0.04 <= x <= 0.06 and 1.0 mol% MnO2 possess excellent electrical properties: d(33)(*)=200-262 pm/V, d(33) = 153-182 pC/N, epsilon(r)=763-976, tan delta=0.054-0.060, T-c=268-312 degrees C. Moreover, samples with single tetragonal phase at x=0.07 have a good temperature stability in the temperature range of 25-150 degrees C due to the shift of the orthorhombic to tetragonal polymorphic phase transition below room temperature. (C) 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved.