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

Abstract

Abstract(1-x-y)BiFeO 3 -x(K 0.5 Bi 0.5 )TiO 3 -y PbTiO 3 piezoelectric ceramics were investigated across the compositional space and contrasted against the BiFeO 3 -(K 0.5 Bi 0.5 )TiO 3 system, a spectrum of relaxor-like/ferroelectric behavior was observed. Structural and piezoelectric properties were found to be closely related to the PbTiO 3 concentration, below a critical concentration, relaxor-type behavior was observed. The mechanisms governing the piezoelectric behavior were investigated with the use of a number of techniques including structural, electrical and imaging techniques. X-ray diffraction established that long-range crystallographic order was promoted 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. PUND analysis was used to confirm electric-field induced polarization measurements, elucidating that the addition of PbTiO 3 increased the switchable polarization and long-range ferroelectric ordering. PFM of the BiFeO 3 -(K 0.5 Bi 0.5 )TiO 3 -PbTiO 3 system exhibited typical domain patterns above a critical PbTiO 3 threshold, with no ferroelectric domains observed in the lead-free 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 efficacious method. The partial substitution of PbTiO 3 into BiFeO 3 -(K 0.5 Bi 0.5 )TiO 3 enables long range crystallographic order, resulting in increased polar order and T C . 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 character in the exploration of new solid-solutions.

The Effect of Niobium Doping on the Electrical Properties of 0.4(Bi0.5K0.5)TiO3-0.6BiFeO3 Lead-Free Piezoelectric Ceramics

“…Values of low-field d 33 are smaller than those measured by other workers [45,46]. The poling conditions used in this study may need optimization.…”

“…The small reduction in the rhombohedral distortion of the unit cell may also have an effect (Table 1). Nb incorporation may also cause the material to become more relaxor-like, which would also explain the reduced hysteresis and negative strain in the unipolar and bipolar strain-electric field loops (Figure 8) [42,45]. …”

Dissolution of four-stage to three-stage dynamic scaling behavior with stabilization of relaxor character in K0.5Bi0.5TiO3 based binary system

“…PNRs responds to the external field much faster than macroscopic domains due to the absence of domain wall motion which results in slim P-E loops and negligible hysteresis in S-E curves [27]. The reduction in S neg with the decrease of non-180°domains and the increase in relaxor character with emergence of PNRs has been enormously reported [23,25,26,28,29]. The difference in the domain dynamics of KLN2 and KLN3 is expected to create a difference in the scaling behavior which is discussed later in this part.…”