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Thermally-induced phase transformations in Na0.5Bi0.5TiO3-KNbO3 ceramics

DOI: 10.1111/jace.14856 DOI Help

Authors: Ge Wang (University of Manchester) , Yizhe Li (University of Manchester) , Claire A. Murray (Diamond Light Source) , Chiu C. Tang (Diamond Light Source) , David A. Hall (University of Manchester)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of The American Ceramic Society , VOL 2

State: Published (Approved)
Published: April 2017
Diamond Proposal Number(s): 10355

Abstract: The structures and functional properties of Na0.5Bi0.5TiO3–xKNbO3 (NBT-xKN) solid solutions, with x in the range from 0.01 to 0.09, were investigated using a combination of high-resolution synchrotron X-ray powder diffraction (SXPD) and ferroelectric property measurements. For low KN contents, an irreversible transformation from cubic to rhombohedral phases was observed after the application of a high electric field, indicating that the polar nanoregions (PNRs) in the unpoled state can be transformed into metastable long-range ordered ferroelectric domains in the poled state. In contrast, the near-cubic phase of the unpoled ceramics was found to be remarkably stable and was retained on cooling to a temperature of 175°C. Upon heating, the field-induced metastable ferroelectric rhombohedral phase transformed back to the nanopolar cubic state at the structural transformation temperature, TST, which was determined as approximately 225°C and 125°C for KN contents of 3% and 5% respectively. For the field-induced rhombohedral phase in the poled specimens, the pseudo-cubic lattice parameter, ap, exhibited an anomalous reduction while the inter-axial angle increased towards a value of 90° on heating, resulting in an overall increase in volume. The observed structural changes were correlated with the results of temperature- dependent dielectric, ferroelectric and depolarization measurements, enabling the construction of a phase diagram to define the stable regions of the different ferroelectric phases as a function of composition and temperature.

Journal Keywords: phase transition; piezoelectric ceramics; relaxor ferroelectric; sodium bismuth titanate; synchrotron Xray

Diamond Keywords: Piezoelectricity; Ferroelectricity

Subject Areas: Materials, Physics, Engineering

Instruments: I11-High Resolution Powder Diffraction

Other Facilities: No

Added On: 10/04/2017 16:05

Discipline Tags:

Engineering & Technology Materials Engineering & Processes Materials Science Ceramics Energy Materials Physics Electronics

Technical Tags:

Diffraction X-ray Powder Diffraction