Institut de Chimie Moléculaire et des Matériaux d'Orsay

Laboratoire d'Etude des Matériaux Hors Equilibre - LEMHE

Functional Oxides

Staff :

Team leader :

Pr. Nita Dragoe    

Assist. Prof :

Dr. David Berardan

Post-doc :

Dr. Lin Pan
  Dr. Nghi Pham    

Technician :

Céline Byl

Ph’D students :

Céline Barreteau
      Thi-Than-Xuan Vo

Our activities are focused on functional oxide materials, with main interest in thermoelectricity and superconductivity.

We also study the influence of the oxygen stoichiometry and of the nanostructuration on these materials properties.

 

Superconductivity

In a superconducting material under a critical temperature Tc and a critical field Hc: - the electrical resistivity falls to zero, which means that the charge carriers can propagate without any loss (see following figure) - the magnetic field is expelled from the material which behaves like an ideal diamagnetic material, and can be used for example in magnetic levitation (inset of the following figure)

Oxypnictides

The superconducting properties of the oxypnictides have been discovered at the beginning of 2008 by a Japanese team (Hosono’s group). The general formula of the undoped parent compound is RFeAsO with R a rare-earth. These compounds crystallize in a layered structure constituted by [R2O2]2+ layers, which act as charge reservoir and transfer the charge carriers induced when doping the materials to the [Fe2As2]2- conducting layer (following figure).

 

Following this discovery, a superconducting behaviour has been observed in several other families that share the same conducting layer. To date, the highest observed critical temperature rearches 55K, with critical fields high that 100 teslas and critical current higher than 106 A.cm-2.

 

 
21 février, 2013