报告题目： Solid refrigeration materials
Solid refrigeration technology based on magnetocaloric, barocaloric/elastocaloric, and eletrocaloric effect has attracted world-wide attention due to the numerous advantages over vapor compression refrigeration which have low efficiencies and negative environmental effects. The coupling of magnetic and structural transition, i.e. magnetostructural transition, is usually sensitive to magnetic field and stress, thereby leading to giant magnetocaloric effect (MCE) and barocaloric/elastocaloric effect.
Here we report stress modulated phase transition and multi-field driven magnetocaloric effect for the well-known La(Fe,Co,Si)13 , Ni2In-type MM'X materials, and RGa/RCo2 compounds. For a room temperature La(Fe,Co,Si)13 magnetocaloric material, enhanced magnetocaloric effect (MCE) by hydrostatic pressure has been demonstrated by magnetic measurements under pressure. To understand the origin, we performed neutron powder diffraction (NPD) studies on the crystal and magnetic structures as a function of temperature under different pressures . The change of atomic local environments and 5 kinds of Fe-Fe bonds (B1-B5) with pressure were illustrated. The result indicates that hydrostatic pressure is an effective way to dig the lattice contribution. Moreover, from the viewpoint of application, magnetocaloric properties of thin plates were studied for La(Fe,Si)13-based materials. Strengthened mechanical properties and enhanced age stability have been achieved in the hydrogenated La(Fe,Si)13H plates as thin as 0.40.6mm with extra Fe or introducing Cu/Pb metal as binders, meanwhile the MCE remains large . MnCoGe-based alloys with magnetostructural transition show giant negative thermal expansion behavior  and MCE, but the bad mechanical properties obstruct their practical applications. We successfully grew Mn-Co-Ge-In films on different substrate, which completely overcome the breakable nature and tunable MCE around room temperature has been observed owing to the stress from substrate . Moreover, we also studied stress modulated spin orientation and magnetic transition in a number of heavy rare earth (R)-based compounds , enhanced MCE has been demonstrated in some of them