Enhanced Field-Induced Strain in the Textured Lead-Free Ceramic

Reactive template grain growth method was applied to prepare <001> grain oriented 0.94(Na_0.52K_0.48)NbO₃–0.06LiNbO₃ ceramics using plate-like NaNbO₃ particles as template. A two-step sintering procedure was put forward to obtain textured ceramics with electromechanical coupling factor k_p = 64%, piezoelectric constant d₃₃ = 220 pC/N, and in practical application the value of available d*₃₃ (converse piezoelectric constant) is about 516 pm/V, which are much higher than these of random form with same composition. Based on the analysis for the behavior of piezoelectricity against the measuring frequency and the intensity of external field, a possible mechanism considering the interaction between defect dipoles induced by the doping of Cu²⁺ and spontaneous polarization dipoles was proposed to elucidate the field-induced giant strain in textured ceramics. This study does not only provide an insight to the origin and coupling effect of two kinds of dipole but also renders a general approach of defect engineering to take advantage of point defect in ceramics realizing certain function enhancement.