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Electric field effect on the microstructure and properties of Ba0.9Ca0.1Ti0.9Zr0.1O3 (BCTZ) lead-free ceramics.

Abstract

The attention in piezoelectric devices has been moved in the past decade to lead-free ceramics, especially on (Ba,Ca)(Ti,Zr)O3-based materials, due to growing environmental concerns. Here we report a systematic evaluation of the effect that the electric field application has on the structure, microstructure and electrical properties in Ba0.9Ca0.1Ti0.9Zr0.1O3 (BCTZ) lead–free ceramics. Powders were prepared by Pechini method. Dense ceramic samples were sintered at 1275°C for 5h. As observed by X ray diffraction (XRD) and energy dispersive x-ray spectroscopy (EDS), the ceramics are single perovskite type structure phase and they are homogeneous both at global and local scale. Rietveld analysis of the diffraction patterns for the non-poled sample is consistent with a coexistence of ferroelectric tetragonal P4mm and rhombohedral R3m symmetries. It is shown that electric field induces changes in rhombohedral–tetragonal relative content that facilitates polarization process of the system. Ceramics exhibit a significant high piezoelectric response with a d33 value as high as ~390pC/N, which is comparable to soft Pb(Zr1-xTix)O3 (PZTs). Scanning Electron Microscopy (SEM) analysis showed an average grain size of 20 μm and complex ferroelectric domains. A confocal Raman spectroscopy and imaging study carried out on both types of samples reveals that, upon application of an electric field, the E(LO3) +A1(LO2) +E(TO4) mode of the Raman spectra shifts to lower frequencies, indicating a reduction of the bonding force between the ions at the B-site of the perovskite (Ti4+, Zr4+) and the oxygen ions of the octahedron for the poled samples. Besides, the spatially resolved mentioned mode of the Raman spectra shows a narrower distribution in the poled sample, monitoring the polarization alignment effect in the direction of the field. These characteristics are related with the complex ferroelectric domain distribution. The polar structure changes after the application of the electric field is revealed, as well by the changes on the dielectric permittivity curves as a function of the temperature. Ceramics also displays a high ferroelectric remnant polarization (Pr=15.3 μC/cm2) and low coercive field (EC=1.5 kV/cm) at room temperature.

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Publication details

The article was received on 07 Nov 2017, accepted on 08 Jan 2018 and first published on 08 Jan 2018


Article type: Paper
DOI: 10.1039/C7TA09798K
Citation: J. Mater. Chem. A, 2018, Accepted Manuscript
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    Electric field effect on the microstructure and properties of Ba0.9Ca0.1Ti0.9Zr0.1O3 (BCTZ) lead-free ceramics.

    A. Reyes, F. Rubio-Marcos, L. Pardo, A. del Campo, R. López-Juárez and M. E. Castrejón, J. Mater. Chem. A, 2018, Accepted Manuscript , DOI: 10.1039/C7TA09798K

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