Ultrahigh strain and piezoelectric behavior in relaxor based ferroelectric single crystals

Abstract

The piezoelectric properties of relaxor based ferroelectric single crystals, such as ${\mathrm{Pb(Zn}}_{\mathrm{1/3}}{\mathrm{Nb}}_{\mathrm{2/3}}{\mathrm{)O}}_{\mathrm{3}}{\mathrm{–PbTiO}}_{\mathrm{3}}$ and ${\mathrm{Pb(Mg}}_{\mathrm{1/3}}{\mathrm{Nb}}_{\mathrm{2/3}}{\mathrm{)O}}_{\mathrm{3}}{\mathrm{–PbTiO}}_{\mathrm{3}}$ were investigated for electromechanical actuators. In contrast to polycrystalline materials such as ${\mathrm{Pb(Zr,Ti)O}}_{\mathrm{3}},$ morphotropic phase boundary compositions were not essential for high piezoelectric strain. Piezoelectric coefficients ${\mathrm{(d}}_{33}$ ’s)>2500 pC/N and subsequent strain levels up to $\text{>0.6\%}$ with minimal hysteresis were observed. Crystallographically, high strains are achieved for 〈001〉 oriented rhombohedral crystals, although 〈111〉 is the polar direction. Ultrahigh strain levels up to 1.7%, an order of magnitude larger than those available from conventional piezoelectric and electrostrictive ceramics, could be achieved being related to an $E$ -field induced phase transformation. High electromechanical coupling ${\mathrm{(k}}_{33}\text{)>90\%}$ and low dielectric loss $\text{<1\%,}$ along with large strain make these crystals promising candidates for high performance solid state actuators.