Large Strain in Relaxor/Ferroelectric Composite Lead-Free Piezoceramics

Abstract

A lead-free relaxor (RE)/ferroelectric (FE) 0-3 composite was developed with a large strain that resulted from the electric-field-induced ergodic relaxor-to-ferroelectric phase transition at a relatively low operational field of 4 kV mm(-1). The composite comprised of 70 vol% 0.91Bi(1/2) Na-1/2 TiO3-0.06BaTiO(3)-0.03AgNbO(3) RE matrix and 30 vol% 0.93Bi(1/2)Na(1/2)TiO(3)-0.07BaTiO(3) FE seed shows a normalized strain, d*(33), of 824 pm V-1 at room temperature. In order to explore the underlying mechanism of this composite effect, two multilayer ceramics with alternating RE and FE layers are also prepared, one with the layers parallel (polarization-coupled multilayer) and the other with the layers perpendicular (strain-coupled multilayer) to the electroded surfaces. It is found that in addition to polarization coupling, the strain coupling effect also plays a critical role in the reduction of the RE-FE phase transition field. The switching dynamics is highlighted with time-dependent piezoforce microscopy in the vicinity of the FE/RE interface