An applied electric field can reversibly change the temperature of an electrocaloric material under adiabatic conditions, and the effect is strongest near phase transitions. We demonstrate a giant electrocaloric effect (0.48 kelvin per volt) in 350-nanometer PbZr(0.95)Ti(0.05)O3 films near the ferroelectric Curie temperature of 222 degrees C. A large electrocaloric effect may find application in electrical refrigeration.

Thermal properties D 3000 Giant Electrocaloric Effect in Thin-Film PbZr 0.95 Ti 0.05 O 3 . -Thin films of the title compound (350 nm) exhibit a giant electrocaloric effect of 0.48 K/V at 226°C near the ferroelectric Curie temperature (222°C) exceeding the previously best results obtained in bulk Pb0.99Nb0.02(Zr0.75Sn0.20Ti0.05)0.98O3 (0.003 K/V at 162°C). A large electrocaloric effect may find application in electrical refrigeration and could provide cooling solutions for electronic components such as computer chips. -(MISCHENKO*, A. S.; ZHANG, Q.; SCOTT, J. F.; WHATMORE, R. W.; MATHUR, N. D.; Sci.

No abstract

A wide class of magnetic molecular materials - molecular clusters with high magnetic moment containing 3d transition metals (such as `Fe8', `Mn12ac', etc) - have been considered from the point of view of their use as refrigerants in low-temperature regions. The consideration was made in the framework of the model based on the Langevin theory of a superparamagnet. The magnetic entropy change caused by a change in an external magnetic field was calculated for various magnetic clusters. The estimations made show that the magnetic molecular clusters could be promising materials for magnetic refrigeration in low-temperature regions (below about 20 K).

No abstract

No abstract

No abstract

New approaches to thermal management of electronic components are of general interest. Our work demonstrates a novel solution for this applications area. Highly effective thermal management solutions can potentially help the semiconductor manufacturers to reduce costs and meet some milestones of the Silicon Roadmap. For example, enormous amount of Joule heating and inability of the state-of-the art coolers to cope with it forces manufacturers to switch to dual-core architectures of processors. Also, our work might inspire a number of blue skies research projects in this particular field because it points to a relatively new approach broadens the scope of applications for ferroelectrics.We have observed [1, 2] large cooling (electrocaloric) effects in thin films under the application of a small electrical voltage. This effect could also be used in reverse to turn low grade waste heat into electricity (pyroelectric energy conversion). In other words, we suggest a way to interconvert thermal end electrical energy. Electrocaloric EffectThe electrocaloric (EC) effect is a change in the temperature of a material under the application of a voltage (electric field). Assuming reversible thermodynamics and Maxwell relations, the EC temperature change T at a temperature T can be described by where the electric field is changed from E 1 to E 2 , P is the polarization, C is the heat capacity, and is the density of a material. The direct measurement of the actual temperature change corresponds to the phenomenologically derived (1) quite well [3,4].The research in the electrocalorics has been exclusively focused on bulk materials [3,4]. The best bulk material for room temperature applications is PbSc 1/2 Ta 1/2 O 3 [5]. Its EC effect is T~1.5 K in the field of about 30 kV cm -1 . This temperature change is not enough for practical applications. However, a prototype cooler has been built [6], and it has been shown experimentally that a properly designed machine can develop a net temperature change about 5× (five times) larger than the EC effect in an individual EC element with T = 1.5 K. Therefore new working elements with large effects are of great interest to assist the thermal management community meet their challenges.We have recently discovered giant EC effects in two thin film materials: T = 12 K in 25 V in 350 nm sol-gel PbZr 0.95 Ti 0.05 O 3 thin film [1], and T = 5 K in 25 V in 260 nm sol-gel PbMg 1/3 Nb 2/3 O 3 -PbTiO 3 [2]. The EC effects were calculated by (1) from P(E) loops measured at different temperatures. More information can be found in the citations. The final result is summarized in Fig. 1. This discovery can ultimately lead to novel cooling devices. 2 1 , 1 E E E dE T P C T T (1) 0 2 4 6 8 10 12 0 100 200 300 T , o C T , K [1] PbZr 0.95 Ti 0.05 O 3 350 nm, 25 V [2] 0.9 PbMg 1/3 Nb 2/3 O 3 -0.1 PbTiO 3 , 260 nm, 25 V Fig. 1. Electrocaloric temperature change T for two materials studied here. Labels in front of the chemical formulas correspond to the citations in the references.Dashed lines represent the effe...