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Mater Sci Nanotechnol 2017
Volume 1 Issue 3 Magnetic Materials 2017
October 09-10, 2017 London, UK
International Conference on
Valérie Paul-Boncour, Materials Science and Nanotechnology
Metal hydride magnetocaloric compounds
Classical refrigeration technology is using refrigerants
(CFC, HCFC, and HFC) which deplete the ozone
layer and contribute to global warming, and are or
will be forbidden by different climate protocols. The
alternative refrigerants (HFO, NH3, H2O …) present also
various drawbacks. Therefore, it is important to develop
new refrigeration technologies without environmental
problems such as magnetic refrigeration based on
the magnetocaloric effect (MCE). Development of
efficient magnetocaloric materials (MCM) for magnetic
refrigeration near room temperature has become
challenging since the discovery of a giant MCE in
Gd(Ge,Si)5 compounds. Intensive studies have yielded
the development of several families of materials, among
which the La(Fe,Si)13 type compounds which display a
giant MCE, are not too expensive and are environmental
friendly. We have developed a rapid method of synthesis
and shaping magnetocaloric La(Fe,Si)13 compounds by
combining high energy ball milling (BM) with reactive
Spark Plasma Sintering (SPS) (Figure 1), a method
which is already used to sinter and shape materials at
an industrial scale. However, the Curie temperatures
of these intermetallics, which is near 200 K, has to
be increased near room temperature by Co for Fe
substitution or light element insertion like hydrogen.
The influence of combining both Fe for Co substitution
and hydrogenation to increase TC above RT and
extend the application of these materials to domestic
heat pump and low-grade heat recuperation will be
presented. We are also searching new MCM families.
The Y1-xRxFe2(H,D)4.2 compounds (R=Gd, Tb) show a
ferro(ferri)-antiferromagnetic transition which display a
giant isotope effect and MCE. This transition is highly
sensitive to any volume changes due to its itinerant
electron metamagnetic behavior. The magnetocaloric
properties of these compounds will be presented and
we will show how the transition temperature can be
shifted near room temperature by appropriate chemical
substitutions.
Figure 1: Influence of the temperature on the piston
displacement and the XRD patterns of sample
pressurized in SPS device. Inset: The magnetic entropy
variation at 1273 K
Biography
Valérie Paul-Boncour has developed her expertise in the structural and physical
properties of metal-hydrides systems since 1983. Hydrogen absorption in metal
and intermetallic induces large structural changes (Cell volume increase, distortion,
superstructure, amorphization) and significant modifications of the electronic and
magnetic properties. She has developed an expertise in the hydrides of RMn
compounds (R= Rare Earth, M=Mn, Fe, Co, Ni) which display a large variety of
original structural and magnetic properties. She has also used the ability of tuning
the magnetic properties by hydrogen absorption to synthetize magnetocaloric
materials for magnetic refrigeration or heat pumps. She belongs to the Institute
of Chemistry and Materials Paris East (ICMPE) created in 2007, which develops
multidisciplinary research activities around four main areas: materials for energy,
nano-materials and scale effects, materials for the environment and sustainable
development, and chemistry at the interface with health and living.
Valérie Paul-Boncour
Institute of Chemistry and Materials Paris East (ICMPE), France