Suchergebnisse

In order to obtain a wide-range magnetoelectric (ME) response on a ME nanocomposite that matches industry requirements, Tb0.3Dy0.7Fe1.92 (Terfenol-D)/CoFe 2 O 4 /P(VDF-TrFE) flexible films were produced by the solvent casting technique and their morphologic, piezoelectric, magnetic and magnetoelectric properties were investigated. The obtained composites revealed a high piezoelectric response (≈−18 pC·N −1 ) that is independent of the weight ratio between the fillers. In turn, the magnetic properties of the composites were influenced by the composite composition. It was found that the magnetization saturation values decreased with the increasing CoFe 2 O 4 content (from 18.5 to 13.3 emu·g −1 ) while the magnetization and coercive field values increased (from 3.7 to 5.5 emu·g −1 and from 355.7 to 1225.2 Oe, respectively) with the increasing CoFe 2 O 4 content. Additionally, the films showed a wide-range dual-peak ME response at room temperature with the ME coefficient increasing with the weight content of Terfenol-D, from 18.6 to 42.3 mV·cm −1 ·Oe −1 . ; The authors thank the FCT-Fundação para a Ciência e Tecnologia—for financial support in the framework of the Strategic Funding UID/FIS/04650/2013 and under project PTDC/EEI-SII/5582/2014. Pedro Martins, Silvia Reis and Marco Silva also acknowledge support from FCT (SFRH/BPD/96227/2013, SFRH/BDE/406 and SFRH/BD/70303/2010 grants, respectively). The authors acknowledge funding by the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R (AEI/FEDER, UE) (including the FEDER financial support). Financial support from the Basque Government Industry Department under the ELKARTEK program is also acknowledged. The authors thank INL, International Iberian Nanotechnology Laboratory, Braga, Portugal, for offering access to their instruments and expertise ; We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI).

The broadband dielectric properties of high sensitivity piezoelectric 0.36BiScO-0.64PbTiO ceramics with average grain sizes from 1.6 μm down to 26 nm were investigated in the 100-500 K temperature range. The grain size dependence of the dielectric permittivity was analysed within the effective medium approximation. It was found that the generalised core-shell (or brick wall) model correctly explains the size dependence down to the nanoscale. For the first time, the grain bulk and boundary properties were obtained without making any assumptions of values of the parameters or simplifications. Two contributions to dielectric permittivity of the grain bulk are described. The first is the size-independent one, which follows the Curie-Weiss law. The second one is shown to plausibly follow the Kittel's law. This seems to suggest the unexpected persistence of mobile ferroelectric domains at the nanoscale (26 nm grains). Alternative explanations are discussed. ; This work was supported by project TUMOCS. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie [Grant Agreement No. 645660]. Financial support of the Spanish MINECO (Project Nos. MAT2014-58816-R and MAT2017-88788-R) and the collaboration in the frame of COST MP0904 Action are highly acknowledged. ; Peer Reviewed

Abstract: In order to obtain a wide-range magnetoelectric (ME) response on a ME nanocomposite that matches industry requirements, Tb0.3Dy0.7Fe1.92 (Terfenol-D)/CoFe2O4/P(VDF-TrFE) flexible films were produced by solvent casting technique and their morphologic, piezoelectric, magnetic and magnetoelectric properties investigated. The obtained composites revealed a high piezoelectric response (≈-18 pC.N-1) that is independent of the weight ratio between the fillers. In turn, the magnetic properties of the composites were influenced by the composite composition. It was found that the magnetization saturation values decreased with increasing CoFe2O4 content (from 18.5 to 13.3 emu.g-1) while the magnetization and coercive field values increased (from 3.7 to 5.5 emu.g-1 and from 355.7 to 1225.2 Oe, respectively) with increasing CoFe2O4 content. Additionally, those films showed a wide-range dual-peak ME response at room temperature with the ME coefficient increasing with weight content of Terfenol-D, from 18.6 mV.cm-1.Oe-1 to 42.3 mV.cm-1.Oe-1. ; FCT-Fundação para a Ciência e Tecnologia—for financial support in the framework of the Strategic Funding UID/FIS/04650/2013 and under project PTDC/EEI-SII/5582/2014. Pedro Martins, Silvia Reis and Marco Silva also acknowledge support from FCT (SFRH/BPD/96227/2013, SFRH/BDE/406 and SFRH/BD/70303/2010 grants, respectively). The authors acknowledge funding by the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R (AEI/FEDER, UE) (including the FEDER financial support). Financial support from the Basque Government Industry Department under the ELKARTEK program is also acknowledged. The authors thank INL, International Iberian Nanotechnology Laboratory, Braga, Portugal, for offering access to their instruments and expertise ...

[EN] Poly(methyl methacrylate-co-methacrylic acid) (PMMA-co-MAA) copolymer containing ionizable moieties is here investigated as a melt processing additive for PVDF to develop high-quality ferro/piezoelectric polymer films by extrusion-calendering. The PVDF/PMMA-co-MAA miscibility and the β-phase crystallization from the melt state at high cooling rates were first explored by Flash DSC. Transposition to the melt-processing of thin films by extrusion-calendering is attempted and a direct production of β-crystals in high amounts is attested at a specific content of 5 wt-% PMMA-co-MAA. Ferro/piezoelectric properties were subsequently investigated and classical ferroelectric-type hysteresis loops clearly appear at room temperature for AC electric fields higher than 900 – 1200 kV/cm. Enhanced remanent polarizations (P) are observed with only 5 wt-% PMMA-based additives and the best ferroelectric performances are identified for PVDF/PMMA-co-MAA blends, in agreement with a higher β-phase content. Stable piezoelectric properties are also highlighted with maximal piezoelectric coefficient (d) of 11 pC/N for these formulations. A linear relationship is found between d and P in accordance with several models and, in this respect, the origin/optimization of the remanent polarization was investigated. Crystal transformations are revealed during high-voltage AC poling and high-quality ferroelectric behaviors with high P values up to 7 µC/cm are obtained at elevated poling temperatures for PVDF/PMMA-co-MAA blends (theoretical d up to 16 pC/N) approaching the theoretical limit value for perfectly-poled β-crystals. This study clearly opens up interesting perspectives in the development of cost-effective electroactive polymer films using industrially-relevant processes and demonstrates that PVDF-based blends with miscible functional PMMA copolymers represent an interesting approach for this purpose. ; Authors gratefully acknowledge the Wallonia Region/Service Public de Wallonie (Belgium), West Vlaanderen Region (Belgium), Agentschap Innoveren Ondernemen (Belgium) and European Commission (FEDER) for the financial support in the framework of the INTERREG V FWVL program (BIOHARV project, GoToS3 portofolio). Authors particularly thank Samuel Devisme from Arkema (France) for supplying raw materials. UMons (LPCM) gratefully acknowledges the Belgian Federal Government Office of Science Policy/Belgian Federal Science Policy Office (SSTC – PAI 6/27, Belgium) for general support and is much indebted to both the Wallonia Region/Service Public de Wallonie (Belgium) and the European Commission (FEDER) for financial support in the frame of phasing-out Hainaut. IMT Lille Douai and Université de Lille acknowledge both the International Campus on Safety and Intermodality in Transportation (CISIT, France), the Hauts-de-France Region (France) and the European Commission (FEDER) for their contributions to funding extrusion equipments, SAXS-WAXS laboratory equipments and calorimetric characterization tools. Authors also thanks the Spanish Ministerio de Economía y Competitividad (MINECO) for financial supports of MAT2017-88788-R and MAT2016-76851-R projects.