Multiphase design induced improved electrical response in BNZ modified (K 0.485 Na 0.485 Li 0.03 )(Nb 0.96 Sb 0.04 )O 3 piezoceramics with high Curie temperature

A detailed investigation of structural, electrical and piezoelectric properties has been performed on lead-free piezoelectric ceramics (1 − x )(K 0.485 Na 0.485 Li 0.03 )(Nb 0.96 Sb 0.04 )O 3 - x (Bi 0.5 Na 0.5 )ZrO 3 [(1 − x )KNNLS- x BNZ], synthesized by traditional solid-state sintering technique. The Rietveld refinement of the XRD patterns confirms the coexistence of rhombohedral–orthorhombic (R–O) and orthorhombic–tetragonal (O–T) phases near room temperature. Temperature-dependent dielectric study reveals that an optimum amount of BNZ in KNNLS can shift the phase transition temperature ( T R–O ) towards room temperature and improve the piezoelectric properties of (1 − x )KNNLS- x BNZ ceramics. For BNZ content of x = 0.015, the (1 − x )KNNLS- x BNZ ceramic exhibits enormous increase in its (i) room temperature dielectric constant ε r by 250% with a simultaneous decrease in the dielectric loss tan δ , and (ii) remnant polarization P r by 120% with a favorable decrease in the coercivity E c , from their corresponding values observed for x = 0. This composition also shows enhanced piezoelectric properties with piezoelectric charge coefficient d 33 = 326 pC/N, and electromechanical coupling factor k p = 39%, and an appreciably higher Curie temperature T c of 335 °C. The improved properties of the composition have been explained on the basis of various features such as crystallite size, lattice strain, grain size, and favorable phase structure of the evolved ceramic system consequent upon addition of BNZ. The study demonstrates that an optimum addition of BNZ in KNNLS can greatly enhance the dielectric, ferroelectric and piezoelectric properties along with the Curie temperature which can widen the scope of using this system in various industrial applications.