Balanced development of piezoelectricity and Curie temperature in (1 − x)K0.44Na0.52Li0.04Nb0.96Sb0.04O3–xBi0.25Na0.25Ba0.5ZrO3 lead-free piezoelectric ceramics

Abstract

(1 − x)K0.44Na0.52Li0.04Nb0.96Sb0.04O3–xBi0.25Na0.25Ba0.5ZrO3 [(1 − x)KNLNS-xBNBZ] (0 ≤ x ≤ 0.05) lead-free piezoelectric ceramics were prepared by using the conventional solid-state reaction method. The relationships among the composition, phase structure, phase volume fraction, microstructure, dielectric, ferroelectric, and piezoelectric properties as well as the phase diagram are established. Rietveld refinements of X-ray diffraction patterns show that with increasing doping level the volume fractions of the orthorhombic and tetragonal phases evolve from 58.7 and 41.3% for x = 0 to 1.7 and 98.3% for x = 0.05, which has strong impacts on the piezoelectric coefficient d 33 and Curie temperature T C. Upon the doping of BNBZ an orthorhombic-tetragonal (O–T) phase boundary forms near room temperature, resulting in an optimum d 33 ~ 288 pC/N, T C ~ 305 °C, a converse piezoelectric coefficient d 33 * ~ 391 pm/V, and a field-induced strain S ~ 0.156% for the x = 0.035 ceramics. These results demonstrate that a balanced development of d 33 and T C can be realized by choosing suitable doping materials and content.