Ultrahigh strain and piezoelectric behavior in relaxor based ferroelectric single crystals

The piezoelectric properties of relaxer based ferroelectric single crystals, such as Pb(Zn1/3Nb2/3)O-3-PbTiO3 and Pb(Mg1/3Nb2/3)O-3-PbTiO3 were investigated for electromechanical actuators. In contrast to polycrystalline materials such as Pb(Zr,Ti)O-3, morphotropic phase boundary compositions were not essential for high piezoelectric strain. Piezoelectric coefficients (d(33)'s)>2500 pC/N and subsequent strain levels up to >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 (k(33))>90% and low dielectric loss <1%, along with large strain make these crystals promising candidates for high performance solid state actuators. (C) 1997 American Institute of Physics.