Electron delocalization enhances the thermoelectric performance of misfit layer compound(Sn_(1-x)Bi_(x)S)_(1.2)(TiS_(2))_(2)

The misfit layer compound(SnS)_(1.2)(TiS_(2))_(2)is a promising low-cost thermoelectric material because of its low thermal conductivity derived from the superlattice-like structure.However,the strong covalent bonds within each constituent layer highly localize the electrons thereby it is highly challenging to optimize the power factor by doping or alloying.Here,we show that Bi doping at the Sn site markedly breaks the covalent bonds networks and highly delocalizes the electrons.This results in a high charge carrier concentration and enhanced power factor throughout the whole temperature range.It is highly remarkable that Bi doping also significantly reduces the thermal conductivity by suppressing the heat conduction carried by phonons,indicating that it independently modulates phonon and charge transport properties.These effects collectively give rise to a maximum ZT of 0.3 at 720 K.In addition,we apply the single Kane band model and the Debye–Callaway model to clarify the electron and phonon transport mechanisms in the misfit layer compound(SnS)_(1.2)(TiS_(2))_(2).

Microstructure and giant baro-caloric effect induced by low pressure in Heusler Co_(51)Fe_(1)V_(33)Ga_(15) alloy undergoing martensitic transformation

Solid-state refrigeration based on the magneto-or mechano-caloric effect,including elasto-and barocaloric in ferroic phase transition materials is promising to replace the current vapor compression refrigeration in consideration of environmental-friendliness and energy-saving.However,both high driven field and small thermal changes in all of these caloric materials hinder the development of solid-state refrigeration.Here we report a giant baro-caloric effect near room temperature induced by a low hydrostatic pressure in Co-based Co_(51)Fe_(1) V_(33)Ga_(15) Heusler alloy.The maximum adiabatic temperature change under the applied pressure change ofΔp=0.1-100 MPa can be as high asΔ_(Tad)^(Max)=7.7 K(Δ_(Tad)^(Max)/Δpreaches up to~7.7 K kbar-1),surpassing theΔ_(Tad)^(Max)/Δpvalue reported hitherto in baro-caloric alloys.In addition,the microstructure is also studied by using the electron microscopes.Along with the austenite and martensite,the submicron V-rich particles are precipitated in this alloy,which are believed to account for enhancing mechanical properties.

Large magnetocaloric effect and magnetoresistance in ErNi single crystal

The magnetic properties,magnetocaloric effect and magnetoresistance in Er Ni single crystal have been investigated in detail.With decreasing temperature,Er Ni single crystal undergoes two successive magnetic transitions:a paramagnetic to ferromagnetic transition at T_(C)=11 K and a spin-reorientation transition at TS_(R)=5 K.Meanwhile,a sharp field-induced metamagnetic transition is observed below the T_(C)along the a axis.Er Ni single crystal possesses a giant magnetocaloric effect around T_(C).The maximum magnetic entropy change is-36.1 J(kg K)^(-1)along the a axis under the field change of 0-50 k Oe.In particular,the rotating magnetocaloric effect in Er Ni single crystal reaches its maximum under a relatively low field,and the maximum rotating entropy change with a value of 9.3 J(kg K)^(-1)is obtained by rotating the applied field from the[011]to[100]directions under 13 k Oe.These results suggest that Er Ni could be a promising candidate for magnetic refrigeration working at liquid-helium temperature region.Moreover,a complicated transport behavior is uncovered in Er Ni single crystal,which is attributed to the complex magnetic states and magnetic polaronic effect.Both positive and negative magnetoresistance are observed.A considerable large magnetoresistance with the value of-34.5%is acquired at 8 K under50 k Oe when the field is along the[100]direction.