Lead-free relaxor ferroelectric materials have attracted attention
due to their field-induced phase transition and its associated strain,
which is an important feature in the use of an actuator [1e6]. Bibased
ferroelectric materials, BiNaTiO3eBaTiO3eKNaNBO3, BiNaKTiO3eBiAlO3,
and Ta-doped BiNaKTiO3, etc. [7e16] exhibited phase
transition with high fields of more than 6e7 kV/mm. To reduce the
field to complete the phase transition, we proposed a concept of an
inclusion-type composite, consisting of relaxor grains and ferroelectric
grains, showing a relatively low field-induced phase transition
[12]. An example describing our concept is shown in Fig. 1.
Fig. 1 shows the concept of an inclusions-embedded composite and
layered composite designed for improving the field-induced phase
transition and its associated deformation behavior. As seen in Fig. 1,
as an electric field was applied, the relaxor or non-polar phase of
the matrix is transformed into a ferroelectric phase. As a
consequence, the field-induced polarization change and strain
were observed