Structure-property relationships in the lead-free piezoceramic system K0.5Bi0.5TiO3 - BiMg0.5Ti0.5O3. (15th April 2019)

• Record Type: Journal Article
• Authors: Zeb, Aurang; Hall, David A.; Aslam, Zabeada; Forrester, Jennifer; Li, Jing-Feng; Li, Yizhe; Tang, Chiu C.; Wang, Ge; Zhu, Fangyuan; Milne, Steven J.
• Is Part Of: Acta materialia. Volume 168(2019)
• Page Start: 100
• Page End: 108
• Publication Date: 2019-04-15
• Subjects: Lead-free piezoelectrics -- Structure-properties -- Potassium bismuth titanate -- Perovskites; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2019.02.011
• Languages: English
• ISSNs: 1359-6454

Abstract

Abstract: Distinctive structure-property relationships are revealed in the relaxor ferroelectric ceramic solid solution, (1-x)K0.5 Bi0.5 TiO3 - xBiMg0.5 Ti0.5 O3 : 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 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, 20 °C) do not coincide with a morphotropic or polymorphic phase boundary. Graphical abstract: Image 1