Variation of Piezoelectric properties and mechanisms across the relaxor-like/Ferroelectric continuum in BiFeO3– (K0.5Bi0.5)TiO3–PbTiO3 ceramics

(1- x - y)BiFeO
₃
-x(K
_0.5
Bi
_0.5
)TiO
₃
-yPbTiO
₃
(BFKBT- PT) piezoelectric ceramics were investigated across the compositional space and contrasted against the xBiFeO
₃
- (1-x)(K
_0.5
Bi
_0.5
)TiO
₃
(BF-KBT) system, whereby a range of relaxor-like/ferroelectric behavior was observed. Structural and piezoelectric properties were closely related to the PbTiO
₃
concentration; below a critical concentration, relaxor-like behavior was identified. The mechanisms governing the piezoelectric behavior were investigated with structural, electrical, and imaging techniques. X-ray diffraction established that longrange non-centrosymmetric crystallographic order was evident above a critical PbTiO
₃
concentration, y > 0.1125. Commensurate with the structural analysis, electric-field-induced strain responses showed electrostrictive behavior in the PbTiO
₃
-reduced compositions, with increased piezoelectric switching in PbTiO
₃
-rich compositions. Positive-up-negative-down (PUND) analysis was used to confirm electric-field-induced polarization measurements, elucidating that the addition of PbTiO
₃
increased the switchable polarization and ferroelectric ordering. Piezoresponse force microscopy (PFM) of the BF-KBT-PT system exhibited typical domain patterns above a critical PbTiO
₃
threshold, with no ferroelectric domains observed in the BF-KBT system in the pseudocubic region. Doping of BiFeO
₃
-PbTiO
₃
has been unsuccessful in the search for high-temperature materials that offer satisfactory piezoelectric properties; however, this system demonstrates that the partial substitution of alternative end-members can be an effective method. The partial substitution of PbTiO
₃
into BF-KBT enables long-range non-centrosymmetric crystallographic order, resulting in increased polar order and TC, compared with the pseudocubic region. The search for novel high-temperature piezoelectric ceramics can therefore exploit the accommodating nature of the perovskite family, which allows significant variance in chemical and physical characters in the exploration of new solid-solutions.