AgBi_(3)S_(5) is a new n-type thermoelectric material that is environmentally friendly and composed of elements of earth-abundant,non-toxic and high performance-cost ratio.This compound features an intrinsically low t...AgBi_(3)S_(5) is a new n-type thermoelectric material that is environmentally friendly and composed of elements of earth-abundant,non-toxic and high performance-cost ratio.This compound features an intrinsically low thermal conductivity derived from its complex monoclinic structure.However,the terrible electrical transport properties greatly limited the improvement of thermoelectric performance.Most previous studies considered that carrier concentration is the main reason for low electrical conductivity and focused on improving carrier concentration by aliovalent ion doping.In this work,we found that the critical parameter that restricts the electric transport performance of AgBi_(3)S_(5)was the extremely low carrier mobility instead of the carrier concentration.According to the Pisarenko relationships and density functional theory calculations,Nb doping can sharpen the conduction band of AgBi_(3)S_(5),which contributes to reducing the effective mass and improving the carrier mobility.With a further increase of the Nb doping content,the conduction band convergence can enlarge the effective mass and preserve the carrier mobility.Combined with the decrease in lattice thermal conductivity due to the intensive phone scattering,a maximum ZT value of~0.50 at 773 K was achieved in Ag_(0.97)Nb_(0.03)Bi_(3)S_(5),which was~109.6%higher than that of pure AgBi3S5.This work will stimulate the new exploration of high-performance thermoelectric materials in ternary metal sulfides.展开更多
基金supported by the National Natural Science Foundation of China(No.52102234 and 51972094),High-level Talents Research Initiation Project of Hebei University(No.521000981421 and 521000981332)and Hebei Province Introduced Overseas Students Funding Project(C20210313).Chen M appreciates the support of the Nature Science Foundation of Hebei Province(A2017201104),and the Natural Science Foundation of Educational Department of Hebei Province(QN2020156).
文摘AgBi_(3)S_(5) is a new n-type thermoelectric material that is environmentally friendly and composed of elements of earth-abundant,non-toxic and high performance-cost ratio.This compound features an intrinsically low thermal conductivity derived from its complex monoclinic structure.However,the terrible electrical transport properties greatly limited the improvement of thermoelectric performance.Most previous studies considered that carrier concentration is the main reason for low electrical conductivity and focused on improving carrier concentration by aliovalent ion doping.In this work,we found that the critical parameter that restricts the electric transport performance of AgBi_(3)S_(5)was the extremely low carrier mobility instead of the carrier concentration.According to the Pisarenko relationships and density functional theory calculations,Nb doping can sharpen the conduction band of AgBi_(3)S_(5),which contributes to reducing the effective mass and improving the carrier mobility.With a further increase of the Nb doping content,the conduction band convergence can enlarge the effective mass and preserve the carrier mobility.Combined with the decrease in lattice thermal conductivity due to the intensive phone scattering,a maximum ZT value of~0.50 at 773 K was achieved in Ag_(0.97)Nb_(0.03)Bi_(3)S_(5),which was~109.6%higher than that of pure AgBi3S5.This work will stimulate the new exploration of high-performance thermoelectric materials in ternary metal sulfides.
