Lead-free Bi(Mg₁/₂Ti₁/₂)O₃-(Bi₁/₂K₁/₂)TiO₃-(Bi₁/₂Na₁/₂)TiO₃ (BMT-BKT-BNT) ceramics have
been shown to exhibit large electromechanical strains under high electric fields along with
negligible fatigue under strong electric fields. To investigate the role of point defects on the
fatigue characteristics, the composition 5BMT-40BKT-55BNT was doped to incorporate acceptor and
donor defects on the A and B sites by adjusting the Bi/Na and Ti/Mg stoichiometries. All samples
had pseudo-cubic symmetries based on x-ray diffraction, typical of relaxors. Dielectric
measurements showed that the high and low temperature phase transitions were largely unaffected by
doping. Acceptor doping resulted in the observation of a typical ferroelectric-like polarization
with a remnant polarization and strain hysteresis loops with significant negative strain.
Donor-doped compositions exhibited characteristics that were indicative of an ergodic relaxor
phase. Fatigue measurements were carried out on all of the compositions. While the A-site
acceptor-doped composition showed a small degradation in maximum strain after 10⁶ cycles, the other
compositions were essentially fatigue free. Impedance measurements were used to identify the
important conduction mechanisms in these compositions. As expected, the presence of defects did not
strongly influence the fatigue behavior in donor-doped compositions owing to the nature of their
reversible field-induced phase transformation. Even for the acceptor-doped compositions, which had
stable domains in the absence of an electric field at room temperature, there was negligible
degradation in the maximum strain due to fatigue. This suggests that either the defects introduced
through stoichiometric variations do not play a prominent role in fatigue in these systems or it is
compensated by factors like decrease in coercive field, an increase in ergodicity, symmetry change,
or other factors.
- Kumar, N., Ansell, T. Y., & Cann, D. P. (2014). Role of point defects in bipolar fatigue behavior of Bi(Mg[subscript 1/2]Ti[subscript 1/2])O₃ modified (Bi[subscript 1/2]K[subscript 1/2])TiO₃-(Bi[subscript 1/2]Na[subscript 1/2])TiO₃ relaxor ceramics. Journal of Applied Physics, 115(15), 154104. doi:10.1063/1.4871671
- The published article can be found at the Journal of Applied Physics.
|Funding Statement (additional comments about funding)
- The National Science Foundation under Grant No. DMR-1308032
- This is the publisher’s final pdf.
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