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 PEMBLC is 11 and 21 μm, 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 μm at +E
_max
and 6.6 μm at -E
_max
with an asymmetry factor (ζ)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 μm while that for -E
_max
is 8 μm with ζ = 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.