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Structure and ferroelectric behaviour of Na 0.5 Bi 0.5 TiO 3 -KNbO 3 ceramics

DOI: 10.1080/17436753.2015.1104053 DOI Help

Authors: G. Wang (University of Manchester) , David Hall (University of Manchester) , T. P. Comyn (University of Leeds) , L. Daniel (GeePs (CNRS UMR8507)) , A. K. Kleppe (Diamond Light Source)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Advances In Applied Ceramics , VOL 115 (2) , PAGES 89 - 95

State: Published (Approved)
Published: January 2016
Diamond Proposal Number(s): 8699

Abstract: Lead-free piezoelectric ceramics, (1-x)Na0.5Bi0.5TiO3-xKNbO3 (NBT-xKN), with x=0.02-0.08 were fabricated by solid state reaction and sintering. The crystal structures and dielectric properties were measured for different KN contents. All compositions in the unpoled, as-sintered state were found to be single phase pseudo-cubic. However, typical ferroelectric behaviour, with well-saturated polarisation-electric field hysteresis loops, was observed for certain compositions at high electric field levels. It is shown using high energy synchrotron XRD that the application of the electric field induced an irreversible structural transformation from the nano-polar pseudo-cubic phase to a ferroelectric rhombohedral phase. The changes in lattice elastic strain and crystallographic texture of a poled NBT-0.02KN specimen as a function of the grain orientation,  conform well to those expected for a conventional rhombohedrally-distorted perovskite ferroelectric ceramic. The dielectric permittivity-temperature relationships for all compositions exhibit two transition temperatures and a frequency–dependent behaviour that is typical of a relaxor ferroelectric. The transition temperatures and grain size decrease with increasing KN content.

Journal Keywords: Lead-free, Piezoelectric ceramic, Domain switching, Phase transformation, Ferroelectric properties, Synchrotron x-ray diffraction

Subject Areas: Materials, Physics, Engineering

Instruments: I15-Extreme Conditions