首页|Rational design and synthesis of Cr1-xTe/Ag2Te composites for solid-state thermoelectromagnetic cooling near room temperature
Rational design and synthesis of Cr1-xTe/Ag2Te composites for solid-state thermoelectromagnetic cooling near room temperature
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Materials with both large magnetocaloric response and high thermoelectric performance are of vital importance for all-solid-state thermoelectromagnetic cooling.These two properties,however,hardly coexist in single phase materials except previously reported hexagonal Cr1-xTe half metal where a relatively high magnetic entropy change(-△SM)of～2.4 J.kg-1·K-1@5 T and a moderate thermoelectric figure of merit(ZT)of～1.2 × 10-2@300 K are simultaneously recorded.Herein we aim to increase the thermoelectric performance of Cr1-xTe by compositing with semiconducting Ag2Te.It is discovered that the in-situ synthesis of Cr1-xTe/Ag2Te composites by reacting their constitute elements above melting temperatures is unsuccessful because of strong phase competition.Specifically,at elevated temperatures(T＞800 K),Cr1-xTe has a much lower deformation energy than Ag2Te and tends to become more Cr-deficient by capturing Te from Ag2Te.Therefore,Ag is insufficiently reacted and as a metal it deteriorates ZT.We then rationalize the synthesis of Cr1-xTe/Ag2Te composites by ex-situ mix of the pre-prepared Cr1-xTe and Ag2Te binary compounds followed by densification at a low sintering temperature of 573 K under a pressure of 3.5 GPa.We show that by compositing with 7 mol％Ag2Te,the Seebeck coefficient of Cr1-xTe is largely increased while the lattice thermal conductivity is considerably reduced,leading to 72％improvement of ZT.By comparison,-△SM is only slightly reduced by 10％in the composite.Our work demonstrates the potential of Cr1-xTe/Ag2Te composites for thermoelectromagnetic cooling.
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