479 research outputs found
Correlation between electric-field-induced phase transition and piezoelectricity in lead zirconate titanate films
We observed that electric field induces phase transition from tetragonal to
rhombohedral in polycrystalline morphotropic lead zirconate titanate (PZT)
films, as reported in 2011 for bulk PZT. Moreover, we evidenced that this
field-induced phase transition is strongly correlated with PZT film
piezoelectric properties, that is to say the larger the phase transition, the
larger the longitudinal piezoelectric coefficient d 33,eff . Although d 33,eff
is already comprised between as 150 to 170 pm/V, our observation suggests that
one could obtain larger d 33,eff values, namely 250 pm/V, by optimizing the
field-induced phase transition thanks to composition fine tuning
Cantilever-based electret energy harvesters
Integration of structures and functions allowed reducing electric
consumptions of sensors, actuators and electronic devices. Therefore, it is now
possible to imagine low-consumption devices able to harvest their energy in
their surrounding environment. One way to proceed is to develop converters able
to turn mechanical energy, such as vibrations, into electricity: this paper
focuses on electrostatic converters using electrets. We develop an accurate
analytical model of a simple but efficient cantilever-based electret energy
harvester. Therefore, we prove that with vibrations of 0.1g (~1m/s^{2}), it is
theoretically possible to harvest up to 30\muW per gram of mobile mass. This
power corresponds to the maximum output power of a resonant energy harvester
according to the model of William and Yates. Simulations results are validated
by experimental measurements but the issues of parasitic capacitances get a
large impact. Therefore, we 'only' managed to harvest 10\muW per gram of mobile
mass, but according to our factor of merit, this puts us in the best results of
the state of the art. http://iopscience.iop.org/0964-1726/20/10/105013Comment: This is an author-created, un-copyedited version of an article
accepted for publication in Smart Materials and Structures. IOP Publishing
Ltd is not responsible for any errors or omissions in this version of the
manuscript or any version derived from it. The definitive
publisher-authenticated version is available online at
doi:10.1088/0964-1726/20/10/105013;
http://iopscience.iop.org/0964-1726/20/10/10501
Cryogenic silicon detectors with implanted contacts for the detection of visible photons using the Neganov-Luke Effect
There is a common need in astroparticle experiments such as direct dark
matter detection, 0{\nu}\b{eta}\b{eta} (double beta decay without emission of
neutrinos) and Coherent Neutrino Nucleus Scattering experiments for light
detectors with a very low energy threshold. By employing the Neganov-Luke
Effect, the thermal signal of particle interactions in a semiconductor absorber
operated at cryogenic temperatures, can be amplified by drifting the
photogenerated electrons and holes in an electric field. This technology is not
used in current experiments, in particular because of a reduction of the signal
amplitude with time which is due to trapping of the charges within the
absorber. We present here the first results of a novel type of Neganov-Luke
Effect detector with an electric field configuration designed to improve the
charge collection within the semiconductor.Comment: 6 pages, 5 figures, submitted to Journal of Low Temperature Physic
Enhanced electrocaloric efficiency via energy recovery.
Materials that show large and reversible electrically driven thermal changes near phase transitions have been proposed for cooling applications, but energy efficiency has barely been explored. Here we reveal that most of the work done to drive representative electrocaloric cycles does not pump heat and may therefore be recovered. Initially, we recover 75-80% of the work done each time BaTiO3-based multilayer capacitors drive electrocaloric effects in each other via an inductor (diodes prevent electrical resonance while heat flows after each charge transfer). For a prototype refrigerator with 24 such capacitors, recovering 65% of the work done to drive electrocaloric effects increases the coefficient of performance by a factor of 2.9. The coefficient of performance is subsequently increased by reducing the pumped heat and recovering more work. Our strategy mitigates the advantage held by magnetocaloric prototypes that exploit automatic energy recovery, and should be mandatory in future electrocaloric cooling devices
Inverse barocaloric effects in ferroelectric BaTiO<inf>3</inf> ceramics
We use calorimetry to identify pressure-driven isothermal entropy changes in ceramic samples of the prototypical ferroelectric BaTiO3. Near the structural phase transitions at ∼400 K (cubic-tetragonal) and ∼280 K (tetragonal-orthorhombic), the inverse barocaloric response differs in sign and magnitude from the corresponding conventional electrocaloric response. The differences in sign arise due to the decrease in unit-cell volume on heating through the transitions, whereas the differences in magnitude arise due to the large volumetric thermal expansion on either side of the transitions.European Research Council (Starting Grant ID: 680032), Engineering and Physical Sciences Research Council (Grant ID: EP/M003752/1), CICyT (Spain) (Project Nos. MAT2013-40590-P and FIS2014-54734-P), DGU (Catalonia) (Project No. 2014SGR00581), SUR (DEC Catalonia), AGAUR, FNR Luxembourg through COFERMAT project, Royal SocietyThis is the final version of the article. It first appeared from American Institute of Physics Publishing via http://dx.doi.org/10.1063/1.496159
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