Piezoelectric-electrostrictive monolithic bi-layer composite flextensional actuator

We propose a new type of flextensional actuator comprised of an electromechanically active element which is a piezoelectric-electrostrictive monolithic bi-layer composite (PE-MBLC) capped by truncated thin brass sheets. The PE-MBLC contains equal amounts of 0.65[Pb(Mg(1/3)Nb(2/3))O(3)]-0.35PbTiO(3) and 0.9[Pb(Mg(1/3)Nb(2/3))O(3)]-0.1PbTiO(3) by volume, and is obtained by a co-sintering process. With applied E(max) = 10 kV/cm unipolar drive, the maximum axial displacement (u(33)) produced by the uncapped and capped PE-MBLC is 11 and 21 microm, respectively. The hysteresis in unipolar u(33) at 0.5 E(max) is 4.6% for the uncapped PE-MBLC, while that for the capped one is 11%. Under bipolar excitation, the maximum u(33) for uncapped is 11.6 microm at +E(max) and 6.6 microm at +E(max) with an asymmetry factor (zeta) of 1.75 for which u(33) < 0 for all E < 0. Under bipolar excitation, the maximum u(33) at +E(max) for the capped PE-MBLC is 19 microm while that for -E(max) is 8 microm with zeta = 2.4, for which u(33) > 0 at -E(max) but is smaller than the u(33) at +E(max). The origins of the observed asymmetry in u(33) are discussed in the context of symmetry superposition and deformation mechanics of the endcaps.