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Enhanced pyroelectric and piezoelectric properties of PZT with aligned porosity for energy harvesting applications†

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      Abstract

      This paper demonstrates the significant benefits of exploiting highly aligned porosity in piezoelectric and pyroelectric materials for improved energy harvesting performance.

      Abstract

      This paper demonstrates the significant benefits of exploiting highly aligned porosity in piezoelectric and pyroelectric materials for improved energy harvesting performance. Porous lead zirconate (PZT) ceramics with aligned pore channels and varying fractions of porosity were manufactured in a water-based suspension using freeze-casting. The aligned porous PZT ceramics were characterized in detail for both piezoelectric and pyroelectric properties and their energy harvesting performance figures of merit were assessed parallel and perpendicular to the freezing direction. As a result of the introduction of porosity into the ceramic microstructure, high piezoelectric and pyroelectric harvesting figures of merits were achieved for porous freeze-cast PZT compared to dense PZT due to the reduced permittivity and volume specific heat capacity. Experimental results were compared to parallel and series analytical models with good agreement and the PZT with porosity aligned parallel to the freezing direction exhibited the highest piezoelectric and pyroelectric harvesting response; this was a result of the enhanced interconnectivity of the ferroelectric material along the poling direction and reduced fraction of unpoled material that leads to a higher polarization. A complete thermal energy harvesting system, composed of a parallel-aligned PZT harvester element and an AC/DC converter, was successfully demonstrated by charging a storage capacitor. The maximum energy density generated by the 60 vol% porous parallel-connected PZT when subjected to thermal oscillations was 1653 μJ cm –3, which was 374% higher than that of the dense PZT with an energy density of 446 μJ cm –3. The results are beneficial for the design and manufacture of high performance porous pyroelectric and piezoelectric materials in devices for energy harvesting and sensor applications.

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      Most cited references 42

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      Charge-carrier dynamics in vapour-deposited films of the organolead halide perovskite CH3NH3PbI3−xClx

      High charge-carrier mobilities and recombination lifetimes are revealed for CH3NH3PbI3−xClx films made by dual-source evaporation. Extracted diffusion lengths approach 3 microns, underlining the high suitability of the evaporated perovskite for planar-heterojunction solar cells.
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        Strong, Tough and Stiff Bioinspired Ceramics from Brittle Constituents

        High strength and high toughness are usually mutually exclusive in engineering materials. Improving the toughness of strong but brittle materials like ceramics thus relies on the introduction of a metallic or polymeric ductile phase to dissipate energy, which conversely decreases the strength, stiffness, and the ability to operate at high temperature. In many natural materials, toughness is achieved through a combination of multiple mechanisms operating at different length scales but such structures have been extremely difficult to replicate. Building upon such biological structures, we demonstrate a simple approach that yields bulk ceramics characterized by a unique combination of high strength (470 MPa), high toughness (22 MPa.m1/2), and high stiffness (290 GPa) without the assistance of a ductile phase. Because only mineral constituents were used, this material retains its mechanical properties at high temperature (600{\deg}C). The bioinspired, material-independent design presented here is a specific but relevant example of a strong, tough, and stiff material, in great need for structural, transportations, and energy-related applications.
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          Improved pyroelectric figures of merit in compositionally graded PbZr1-xTixO3 thin films.

          Pyroelectric materials have been widely used for a range of thermal-related applications including thermal imaging/sensing, waste heat energy conversion, and electron emission. In general, the figures of merit for applications of pyroelectric materials are proportional to the pyroelectric coefficient and inversely proportional to the dielectric permittivity. In this context, we explore single-layer and compositionally graded PbZr1-xTixO3 thin-film heterostructures as a way to independently engineer the pyroelectric coefficient and dielectric permittivity of materials and increase overall performance. Compositional gradients in thin films are found to produce large strain gradients which generate large built-in potentials in the films that can reduce the permittivity while maintaining large pyroelectric response. Routes to enhance the figures of merit of pyroelectric materials by 3-12 times are reported, and comparisons to standard materials are made.
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            Author and article information

            Affiliations
            [a ] Department of Mechanical Engineering , University of Bath , BA2 7AY , UK . Email: C.R.Bowen@ 123456bath.ac.uk
            [b ] State Key Laboratory of Powder Metallurgy , Central South University , 410083 , China . Email: dzhang@ 123456csu.edu.cn
            Journal
            J Mater Chem A Mater Energy Sustain
            J Mater Chem A Mater Energy Sustain
            Journal of Materials Chemistry. A, Materials for Energy and Sustainability
            Royal Society of Chemistry
            2050-7488
            2050-7496
            14 April 2017
            06 March 2017
            : 5
            : 14
            : 6569-6580
            5436493 c7ta00967d 10.1039/c7ta00967d
            This journal is © The Royal Society of Chemistry 2017

            This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial 3.0 Unported License ( http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

            Categories
            Chemistry

            Notes

            †Electronic supplementary information (ESI) available. See DOI: 10.1039/c7ta00967d

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