Structure Property Relationships in the Lead-free Piezoceramic System K0.5Bi0.5TiO3 - BiMg0.5Ti0.5O3

David Hall, Yizhe Li, Steven Milne (Corresponding), Aurang Zeb (Lead)

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Abstract

Distinctive structure-property relationships are revealed in the relaxor ferroelectric ceramic solid solution, (1-x)K0.5Bi0.5TiO3 - xBiMg0.5Ti0.5O3: 0.02 < x < 0.08. The constructed phase diagram and results of in-situ synchrotron X-ray diffraction provide explanations for temperature and electric field dependent anomalies in dielectric, ferroelectric and electromechanical properties. At room temperature a mixed phase tetragonal and pseudocubic phase field occurs for compositions 0 > x ≤ 0.07. As temperature rises to ≥ 150 °C, the ferroelectric tetragonal relaxor phase changes to a pseudocubic ergodic relaxor phase; this change in length scale of polar order is responsible for an inflection in relative permittivity - temperature plots. The transition is reversed by a sufficient electric field, thereby explaining the constricted form of polarisation-electric field loops measured at >150°C. It is also responsible for a change in slope of the strain-electric field (S-E) plots which are relatively linear in the ferroelectric regime i.e. at temperatures up to 150 °C, giving unipolar strains of 0.11 % at 20 °C and 0.14% at 150 °C (50 kV cm-1 field). The additional contribution from the effect of the field-induced pseudocubic to tetragonal transition, generates strains of ∼ 0.2 % at 185 °C. Unusual for a piezoelectric solid solution, the maximum strains and charge coefficients (d33 =150 pC N-1, 20 °C) do not coincide with a morphotropic or polymorphic phase boundary.
Original languageEnglish
Article number10.1016/j.actamat.2019.02.011
JournalActa Materialia
Early online date14 Feb 2019
DOIs
Publication statusPublished - 2019

Keywords

  • piezoceramics
  • Lead-free
  • Phase transition
  • Ferroelectric properties
  • Synchrotron x-ray diffraction

Research Beacons, Institutes and Platforms

  • Advanced materials
  • Manchester Energy

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