Dielectric, Piezoelectric Properties and Field-Induced Large Strain of Bi(Zn0.5Ti0.5)O3-Modified Morphotropic Phase Boundary Bi0.5(Na0.82K0.18)0.5TiO3 Piezoelectric Ceramics

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In this study, the effects of Bi(Zn0.5Ti0.5)O3 (BZT) on the structure, dielectric, ferroelectric, and piezoelectric properties of morphotropic phase boundary Bi0.5(Na0.82K0.18)0.5TiO3 (BNKT18) piezoelectric ceramics were investigated. In the composition range studied, X-ray diffraction results revealed the coexistence of rhombohedral and tetragonal phases. It was found that BZT content decreased the depolarization temperature (T_{\text{d}}) of BNKT18--BZT ceramics, and the degree of diffuseness of the phase transition became more obvious with increasing BZT content. The addition of a small amount of BZT improved the piezoelectric properties, with the maximum piezoelectric constant (d_{33}=166 pC/N) and electromechanical coupling factor (k_{\text{p}}=31.7%) obtained at x=0.03. However, at a high concentration of BZT, the remanent polarization and piezoelectric constant d_{33} were drastically decreased, and a pronounced enhancement in electric field-induced strain was observed, with a peak of {\sim}0.27% at x=0.07, which corresponds to a normalized strain, S_{\text{max}}/E_{\text{max}}, of {\sim}385 pm/V.
2012-09-25