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 (εr) ∼648, dielectric loss (tan δ) ∼0.05 at 100 kHz, a relatively high density (ρ) ∼4.49 g/cm3, remnant polarization (Pr) ∼11.76 μC/cm2, coercive field (Ec) ∼9.81 kV/cm, Curie temperature (Tc) ∼372 °C and piezoelectric coefficient (d33) ∼71 pC/N observed in K0.50N0.50NbO3 suggested that it can be an important lead free ferroelectric material.