High electromechanical response in the non morphotropic phase boundary piezoelectric system PbTiO3−Bi(Zr1/2Ni1

Abstract

There is a general perception that a large piezoelectric response in ferroelectric solid solutions requires a morphotropic/polymorphic phase boundary (MPB/PPB), i.e., a composition driven inter-ferroelectric instability. This correlation has received theoretical support from models which emphasize field driven polarization rotation and/or inter-ferroelectric transformations.Here, we show that the ferroelectric system (1-x)PbTiO3-(x)Bi(Zr1/2Ni1/2)O3 (PT-BNZ), which shows d33 (~ 400 pC/N) comparable to the conventional MPB/PPB systems, does not belong to this category. In the unpoled state the compositions of PT-BNZ showing large d33 exhibits a coexistence of tetragonal and cubic-like (CL) phases on the global length scale. A careful examination of the domain strucures and global structures (both in the unpoled and poled states) revealed that the CL phase has no symptom of average rhombohedral distortion even on the local scale. The CL phase is rather a manifestation of tetragonal regions of short coherence length. Poling increases the coherence length irreversibly which manifests as poling induced CL P4mm transformation on the global scale. PT-BNZ is therefore qualitatively different from the conventional MPB piezoelectrics. In the absence of the composition and temperature driven inter-ferroelectric instability in this system, polarization rotation and inter-ferroelectric transformation are no longer plausible mechanisms to explain the large electromechanical response. The large piezoelectricity is rather associated with the increased structural-polar heterogeneity due to domain miniaturization without the system undergoing a symmetry change. Our study proves that attainment of large piezoelectricity does not necessarily require inter-ferroelectric instability (and hence morphotropic/polymorphic phase boundary) as a criterion.

Energy harvesting with flexible piezocomposite fabricated from a biodegradable polymer

“…As seen clearly from the pseudo cubic {200 pc } Bragg profile shown in Figure 3A,B, the cubic phase feature tends to supress on poling at the expense of increasing tetragonal phase fraction. Increase in tetragonal phase fraction can be assigned to growth of ferroelectric domain on application of electric field as shown clearly by Rishikesh et al 22 Cubic domains are nothing but tetragonal domains with short coherence length. Similarly, {200 pc } Bragg reflection peak in Figure 3C for BTS as reported earlier 19,23 shows structural coexistence of orthorhombic and tetragonal phases.…”

“…The X‐ray diffraction pattern of PCL‐PT‐BNZ and PCL‐BST composite is shown in Figure 2A,B. Excellent electromechanical properties of PT‐BNZ has been attributed to structural phase co‐existence of tetragonal and cubic 22 . As seen clearly from the pseudo cubic {200 pc } Bragg profile shown in Figure 3A,B, the cubic phase feature tends to supress on poling at the expense of increasing tetragonal phase fraction.…”

A comparative study of energy harvesting performance of polymer‐piezoceramic composites fabricated with different piezoceramic constituents

“…5,33 The dense ceramic form of PT-BNZ shows d 33 of 400 pC/N. 34 Our focus here is to understand the role of grain size of the piezoceramic constituents in determining the overall energy harvesting performance of the composites. For the sake of meaningful comparison of the results, we have kept the relative volume fraction of the ceramic and polymer same in all cases.…”

“…For the sake of detailed comparison, we have also included our previous results on PVDF‐0.59PbTiO 3 ‐0.41Bi(Zr 0.5 Ni 0.5 )O 3 (PT‐BNZ) composite 5,33 . The dense ceramic form of PT‐BNZ shows d 33 of ~400 pC/N 34 . Our focus here is to understand the role of grain size of the piezoceramic constituents in determining the overall energy harvesting performance of the composites.…”

Finite-size-effect on a very large length scale in NBT-based lead-free piezoelectrics

“…The cubic phase has been inserted as a matter of convenience to account for the misfits. [37][38][39][40][41] The rhombohedral lattice strain ð90 ○ -αÞ derived from the refined lattice parameters of poled NBT1150 is 0.28 ○ and that of poled NBT1200 is 0.39 ○ , i.e., the large grain specimen exhibits more rhombohedral distortion as compared to the small grain specimen. The phase fraction of long-range ferroelectrically ordered R3c phase was found to be 60% for poled NBT1150 and 84% for poled NBT1200.…”