Chairs
Emmanuel Defay, Luxembourg Institute of Science and Technology (LIST), Luzembourg
Emmanuel Defay, Luxembourg Institute of Science and Technology (LIST), Luzembourg
Emmanuel Defay has been working on the integration of dielectric and piezoelectric materials into Microsystems for 19 years. He completed his PhD at INSA Lyon (Fr.) in 1999 and stayed with CEA LETI Grenoble (Fr.) from 2000 to 2014. He is now leading the group "Ferroic Materials for Transducers" at the Luxembourg Institute of Science and Technology (Lu.) where he arrived in 2014. His scientific interests are mostly in piezoelectric films and electrocaloric devices. From 2010 to 2012, he was invited scholar in Pr Mathur's team at the University of Cambridge (UK) to study the electrocaloric effect and more specifically its energy efficiency. Emmanuel has published two books, 100 scientific papers and filed 30 patents.
09:05-09:30
Design of polar-dielectrics for electrocaloric cooling
Dr Qiming Zhang, Pennsylvania State University, USA
Abstract
The direct and efficient coupling between the electric signals and the elastic, thermal, optical and magnetic signals in ferroelectrics makes them attractive for exploring a broad range of cross-coupling phenomena which have great promise for new device technologies. This talk will present the recent advances at Penn State in developing electrocaloric materials which may provide alternative cooling technology to the century old vapor compression cycle (VCC) based cooling. Electrocaloric effect (ECE), which is the temperature and/or entropy change of dielectric materials caused by the electric field induced polarization change, is attractive to realize efficient cooling devices. Recently, we demonstrated that large ECE can be achieved in several classes of ferroelectric materials with tailored nano- and meso-structures. Experimental results on the ECE in the relaxor ferroelectric polymers and general theoretical considerations for achieving large ECE will be presented. This talk will also discuss considerations on and present recent works in using nanocomposites to further enhancing the ECE beyond the pure relaxor polymers, on the giant ECE in a class of dielectric liquid, and in ferroelectric ceramics near the invariant critical point. The works related to developing the EC cooling devices, making use of the newly developed large ECE in ferroelectric materials and featuring high cooling power density and high efficiency, will also be presented.
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Dr Qiming Zhang, Pennsylvania State University, USA
Dr Qiming Zhang, Pennsylvania State University, USA
Dr. Qiming Zhang: Distinguished Professor of Engineering of Penn State University, USA. The research areas in his group include fundamentals and applications of electronic and electroactive materials. During more than 20 years at Penn State, he has conducted research covering dielectrics and charge storage devices, electrocaloric effect and solid state cooling devices, polymer thin film devices, polymer MEMS, actuators, sensors, transducers, and electro-optic and photonic devices. He has over 400 publications and 15 patents in these areas. He is the recipient of the 2008 Penn State Engineering Society Premier Research Award, the 2015 Penn State Faculty Scholar Medal, and a Fellow of IEEE and a Fellow of APS.
09:45-10:15
Multicaloric propertires of P(VDF-TrFE-CTFE) terpolymer
Dr Gael Sebald, Université de Lyon, INSA-Lyon, LGEF, France
Abstract
In the framework of caloric materials, electrocaloric effect on the one hand and elastocaloric effect on the other hand may be used for cooling systems. Electrocaloric effect refers to the electric field driven entropy change whereas elastocaloric effect refer to strain-driven entropy change. In some materials, such as P(VDF-TrFe-CTFE) and P(VDF-TrFe-CFE) terpolymer, both effects may exist. In this presentation, the characterization of the electrocaloric effect of terpolymer is presented. It is based on two complementary direct characterizations. In a first experiment, the isothermal heat exchange is measured upon the application of electric field steps using modified Differential Scanning Calorimetry equipment. In a second experiment, the adiabatic temperature change is measured upon fast electric field variation using a thermal imaging camera. It is shown that both characterizations are consistent. In case of elastocaloric effect, the characterization technique is first presented and the results obtained on stretched terpolymer are presented and compared to other elastocaloric materials such as natural rubber. The entropy variation in case of electrocaloric effect is believed to be related to the polar phase whereas elastocaloric effect is better related to the amorphous phase entropy. Based on thermodynamics considerations, theoretical conditions for the additivity of both effects are finally presented and discussed
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Dr Gael Sebald, Université de Lyon, INSA-Lyon, LGEF, France
Dr Gael Sebald, Université de Lyon, INSA-Lyon, LGEF, France
Gael Sebald graduated with a Ph. D. degree in acoustics in 2004 from INSA-Lyon (Lyon, France) for his work on single crystals with ultra high electromechanical coupling. He was then a Japan Society for Promotion of Science fellow (JSPS) (2004-2005) for a post-doctoral position at Tohoku University (Japan) where he developed fabrication, modeling and characterization of metal-cored piezoelectric fibers. Since 2005, Gael Sebald is associate professor at INSA Lyon (Lyon, France). After several developments on electrocaloric materials characterization, he developed energy harvesting from temperature fluctuations using the same materials. In 2010, he was a one-year Invited Researcher Fellow from JSPS to work at Tohoku University (Japan) on nonlinear energy harvesting and MEMS energy harvesters. His main research interests are smart materials characterization and applications, hysteresis modeling, multiphysics coupling in smart materials (especially piezoelectric, electrostrictive and electrocaloric couplings), and energy harvesting on vibration and heat.
11:00-11:30
Electrocaloric effect of antiferroelectric thick films
Dr Qi Zhang, Cranfield University, UK
Abstract
When a sufficiently high external electric field is applied to an antiferroelectric (AFE) material, a ferroelectric state can be induced in AFE, and this phase transition is often accompanied by larger strains and polarization changes, and normally occurs at far lower temperature than its Curie temperature. Therefore, Pb-based AFE materials have attracted increasing attention for the potential applications in cooling devices through electrocaloric effect near room temperature. Thick (1-100 μm) films possess large breakdown strength that bulk materials lack and relatively large heat-sinking capacity compared with thin films.
In this work, antiferroelectric (AFE) thick films (1 μm) of (Pb(1-3x/2)Lax)(Zr1-yTiy)O3 with x = 0.08 -0.14 and their compositionally graded multilayer thick films were deposited on LaNiO3/Si(100) substrates by using a sol-gel method. A large reversible adiabatic temperature change of ΔT = 25 ºC was presented in the PLZT thick film with x=0.08 at 127 ºC at 990 kV/cm and also a large reversible adiabatic ΔT (=28 ºC) was presented in the compositionally graded thick films at room temperature at 900 kV/cm. The refrigerant capacities (ΔT x ΔS) of the compositional graded thick films and single composition PLZT thick film with x = 0.08 show comparable values with the best thin films’ values. These properties of the thick AFE films indicate that the thick films have strong potential application in cooling devices.
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Dr Qi Zhang, Cranfield University, UK
Dr Qi Zhang, Cranfield University, UK
Dr Qi Zhang received the BSc from Wuhan University, Wuhan, China in 1982, the M Eng from Wuhan University of Technology, Wuhan, China in 1986 and the PhD degree from Chemistry Department, Monash University, Australia, in 1995.
In 1996, he joined the Nanotechnology Group, Cranfield University as a Research Officer, where he continued his research into thin film preparation by sol-gel processing. These thin film materials include complex metal oxides with ferroelectric and piezoelectric properties. In 1999, he became a Senior Research Fellow and continued to develop sol-gel spin coating technology for various inorganic thin films. In 2007 he became a senior lecturer and started working on materials for energy storage and the fabrication of nanomaterials and devices. He is currently a visiting professor in Wuhan University of Technology recruited under Hubei “one hundred people” program. He is a fellow of Institute of Materials, Minerals and Mining, UK. He is also a charted scientist. He has authored or co-authored 150 journal and conference papers with h index 23 and several chapters in books. He edited the book “Electrocaloric Materials” by Springer in 2013. His main areas of research are Materials synthesis and functional materials, nanoink formulation for directly ink-jet printing. His research also includes synthesis of nanomaterials, and manufacturing membranes for CO2 capture.
12:45-13:15
Electrocaloric and elastocaloric effects in soft materials
Professor Zdravko Kutnjak, Jozef Stefan Institute, Slovenia
Abstract
Materials with large caloric effect have the promise of realizing solid state refrigeration which is more efficient and environmentally friendly compared to current techniques. A review of recent direct measurements of the large electrocaloric effect in liquid crystalline materials and large elastocaloric effect in liquid crystal elastomers will be given. In liquid crystalline materials and mixtures of liquid crystals with functionalized nanoparticles the electrocaloric effect exceeding 8 K was found in the vicinity of the isotropic to smectic phase transition. Direct measurements indicate that the elastocaloric response of similar magnitude can be found in main-chain liquid crystalline elastomers. Both soft materials can play significant role as active cooling elements and parts of thermal diodes or regeneration material in development of new cooling devices.
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Professor Zdravko Kutnjak, Jozef Stefan Institute, Slovenia
Professor Zdravko Kutnjak, Jozef Stefan Institute, Slovenia
Dr Kutnjak has obtained Ph.D. degree in physics in 1994 at the University of Ljubljana. After two years of postdoctoral work at Massachusetts Institute of Technology, Dr Kutnjak returned to Jozef Stefan Institute, where as a head of the laboratory for calorimetry and dielectric spectroscopy and Professor at the University of Ljubljana continues research of ordered and disordered systems. His work is mainly focused on relaxor ferroelectrics, multiferroics, liquid crystal elastomers and various confined systems. Presently, he is involved in research and development of materials for novel electrocaloric cooling technologies.
13:30-14:00
Trajectories through parameter space of electrocaloric lead scandium tantalate
Sam Crossley, Stanford University, USA
Abstract
Measurements of electrocaloric (EC) effects can be challenging in various ways. I will review a variety of strategies that have been developed to meet these challenges over the past decade, and present fresh measurement protocols using lead scandium tantalate. Notably, I will show how to deduce EC temperature change from adiabatic contours on maps of total entropy. Separately, I will show how equivalent results may be obtained from electrical measurements in which thermodynamic conditions are varied via the measurement timescale
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Sam Crossley, Stanford University, USA
Sam Crossley, Stanford University, USA
Sam Crossley studied Natural Sciences at King's College, Cambridge as an undergraduate. His doctoral research at Cambridge with Professor Neil Mathur focussed on the electrocaloric properties of a variety of thin film and bulk materials and devices. His experimental work developed and applied bespoke measurement apparatus, and was supported by finite-element and analytical modelling of heat flow. He has authored scientific papers and review articles in the fields of electrocaloric materials and piezoelectric energy harvesting materials. His postdoctoral research on energy materials is with Professor Harold Hwang at Stanford University and SLAC National Accelerator Laboratory.
14:45-15:30
Poster session