By virtue of the excellent plasticity and tunable transport properties,Ag_(2)S-based materials demonstrate an intriguing prospect for flexible or hetero-shaped thermoelectric applications.Among them,Ag_(2)S_(1-x)Te_(x...By virtue of the excellent plasticity and tunable transport properties,Ag_(2)S-based materials demonstrate an intriguing prospect for flexible or hetero-shaped thermoelectric applications.Among them,Ag_(2)S_(1-x)Te_(x)exhibits rich and interesting variations in crystal structure,mechanical and thermoelectric transport properties.However,Te alloying obviously introduces extremely large order-disorder distributions of cations and anions,leading to quite complicated crystal structures and thermoelectric properties.Detailed composition-structure-performance correlation of Ag_(2)S_(1-x)Te_(x)still remains to be established.In this work,we designed and prepared a series of Ag_(2)S_(1-x)Te_(x)(x=0-0.3)materials with low Te content.We discovered that the monoclinic-to-cubic phase transition occurs around x=0.16 at room temperature.Te alloying plays a similar role as heating in facilitating this monoclinic-to-cubic phase transition,which is analyzed based on the thermodynamic principles.Compared with the monoclinic counterparts,the cubic-structured phases are more ductile and softer in mechanical properties.In addition,the cubic phases show a degenerately semiconducting behavior with higher thermoelectric performance.A maximum zT=0.8 at 600 K and bending strain larger than 20% at room temperature were obtained in Ag_(2)S_(0.7)Te_(0.3).This work provides a useful guidance for designing Ag_(2)S-based alloys with enhanced plasticity and high thermoelectric performance.展开更多
Superionic conductors,which exhibit liquid-like phonon transport but crystal-like carrier transport,have attracted great attention and broad research interest in the thermoelectric community.Ag_(2)Te is a superionic c...Superionic conductors,which exhibit liquid-like phonon transport but crystal-like carrier transport,have attracted great attention and broad research interest in the thermoelectric community.Ag_(2)Te is a superionic conductor;however,its small band gap and large Ag vacancy formation energy impede its application as a prominent p-type thermoelectric material.In this work,synergistic optimization of the thermoelectric performance of Ag_(2)Te through Cu substitution is realized through a combination of experimental and theoretical efforts.For the electrical transport,Cu substitution systematically increases the band gap of Ag_(2)Te and reduces the cation vacancy formation energy.These two beneficial effects simultaneously increase the electrical conductivity and suppress the bipolar effect,thereby greatly enhancing the p-type electrical transport properties of Ag_(2)Te.For the thermal transport,alloying Cu_(2)Te with Ag_(2)Te significantly reduces the thermal conductivity through not only point defect scattering but also softening of the interatomic interactions.The latter is attributed to the relatively small Cu atoms vibrating in the oversized 8c sites.This two-fold optimization results in maximum thermoelectric figure of merit zT values of over 1.3 at 773 K for both Ag_(1.2)Cu_(0.8)Te and AgCuTe,demonstrating the great potential of Ag_(2-x)Cu_(x)Te as a promising p-type thermoelectric material system.展开更多
基金This work is supported by the National Key Research and Development Program of China(2018YFB0703600)National Natural Science Foundation of China(91963208,51625205,51961135106,51802333)+2 种基金the CAS-DOE Program of Chinese Academy of Sciences(121631KYSB20180060)the Shanghai Government(20JC1415100)the Swedish Research Council(VR 2018e06030).
文摘By virtue of the excellent plasticity and tunable transport properties,Ag_(2)S-based materials demonstrate an intriguing prospect for flexible or hetero-shaped thermoelectric applications.Among them,Ag_(2)S_(1-x)Te_(x)exhibits rich and interesting variations in crystal structure,mechanical and thermoelectric transport properties.However,Te alloying obviously introduces extremely large order-disorder distributions of cations and anions,leading to quite complicated crystal structures and thermoelectric properties.Detailed composition-structure-performance correlation of Ag_(2)S_(1-x)Te_(x)still remains to be established.In this work,we designed and prepared a series of Ag_(2)S_(1-x)Te_(x)(x=0-0.3)materials with low Te content.We discovered that the monoclinic-to-cubic phase transition occurs around x=0.16 at room temperature.Te alloying plays a similar role as heating in facilitating this monoclinic-to-cubic phase transition,which is analyzed based on the thermodynamic principles.Compared with the monoclinic counterparts,the cubic-structured phases are more ductile and softer in mechanical properties.In addition,the cubic phases show a degenerately semiconducting behavior with higher thermoelectric performance.A maximum zT=0.8 at 600 K and bending strain larger than 20% at room temperature were obtained in Ag_(2)S_(0.7)Te_(0.3).This work provides a useful guidance for designing Ag_(2)S-based alloys with enhanced plasticity and high thermoelectric performance.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51772186,51632005,51761135127,and 51371194)National Key Research and Development Program of China(No.2018YFB0703600)the research grant(No.16DZ2260601)from Science and Technology Commission of Shanghai Municipality.
文摘Superionic conductors,which exhibit liquid-like phonon transport but crystal-like carrier transport,have attracted great attention and broad research interest in the thermoelectric community.Ag_(2)Te is a superionic conductor;however,its small band gap and large Ag vacancy formation energy impede its application as a prominent p-type thermoelectric material.In this work,synergistic optimization of the thermoelectric performance of Ag_(2)Te through Cu substitution is realized through a combination of experimental and theoretical efforts.For the electrical transport,Cu substitution systematically increases the band gap of Ag_(2)Te and reduces the cation vacancy formation energy.These two beneficial effects simultaneously increase the electrical conductivity and suppress the bipolar effect,thereby greatly enhancing the p-type electrical transport properties of Ag_(2)Te.For the thermal transport,alloying Cu_(2)Te with Ag_(2)Te significantly reduces the thermal conductivity through not only point defect scattering but also softening of the interatomic interactions.The latter is attributed to the relatively small Cu atoms vibrating in the oversized 8c sites.This two-fold optimization results in maximum thermoelectric figure of merit zT values of over 1.3 at 773 K for both Ag_(1.2)Cu_(0.8)Te and AgCuTe,demonstrating the great potential of Ag_(2-x)Cu_(x)Te as a promising p-type thermoelectric material system.