Synthesis and characterizations of KNN ferroelectric ceramics near 50/50 MPB

Lead free ferroelectric ceramics near the morphotropic phase boundary (MPB) of KxNa1-x(NbO3)/KNN system (where x=0.48, 0.50, 0.52) were synthesized in the single perovskite phase by the partial co-precipitation synthesis route. The compositional dependences of phase, structure and electrical properties were studied in detail. X-ray diffraction (XRD) study revealed the coexistence of orthorhombic and monoclinic structures in K0.50N0.50NbO3. SEM characterization of the sintered KNN ceramics revealed dense and homogeneous packing of grains. Room temperature (RT) dielectric constant (epsilon(r)) similar to 648, dielectric loss (tan delta) similar to 0.05 at 100 kHz, a relatively high density (rho) similar to 4.49 g/cm(3), remnant polarization (P-r) similar to 11.76 mu C/cm(2), coercive field (E-c) similar to 9.81 kV/cm, Curie temperature (T-c) similar to 372 degrees C and piezoelectric coefficient (d(33)) similar to 71 pC/N observed in K0.50N0.50NbO3 suggested that it can be an important lead free ferroelectric material. (C) 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved.