Resolving structural contributions to the electric-field-induced strain in lead-free (1-x)Ba(Zr0.2Ti0.8)O3 - x(Ba0.7Ca0.3)TiO3 piezoceramics

The large signal macroscopic strain response during an applied bipolar electric field is calculated from field-dependent in situ XRD data using expressions for, first, a lattice strain contribution and, second, a ferroelastic strain contribution. The lattice strain contribution is estimated using a weighted average of the lattice strains for the observed reflections along the field direction. The ferroelastic strain contribution is calculated by integrating the lattice parameter changes weighted with the ferroelastic domain distribution over all orientations relative to the direction of the applied field. Structural parameters are determined by means of both single peak fitting and Rietveld refinements. A large ferroelastic contribution is found for tetragonal (1 - x)Ba(Zr0.2Ti0.8)O-3 - x(Ba0.7Ca0.3)TiO3 materials that appears to be the dominant origin for the large signal macroscopic strain. The strong changes in lattice parameters and the decrease in tetragonality as a function of orientation and electric field also indicate a large influence of microstructure constraints on the macroscopic strain response. The total strain calculated from X-ray diffraction using both methods is in good agreement with macroscopic strain measurements. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.