Zintl phases with the nominal compositions Ca_(1-δ)Ce_(δ)Ag_(1-δ)Sb(RE=La,Ce,Pr,Nd,Sm;δ≈0.15)are interesting due to their unique crystal structures and potential as high temperature thermoelectrics.Their structur...Zintl phases with the nominal compositions Ca_(1-δ)Ce_(δ)Ag_(1-δ)Sb(RE=La,Ce,Pr,Nd,Sm;δ≈0.15)are interesting due to their unique crystal structures and potential as high temperature thermoelectrics.Their structures generally feature the LiGaGe type structure with substantial vacancies on the Ag sites.The formation of such defects can be explained by the electronic effects,with which 18 electrons are required to stabilize the CaAgSb Zintl system.Since the substitution of Ca^(2+)with RE^(3+)will lead to electron excess,the formation of Ag defects will be an intrinsic character of such compounds to maintain their electron precise nature.In this work,the material Ca_(0.85)Ce_(0.15)Ag_(0.85)Sb was selected for a detailed study on defect chemistry.In order to better understand the mechanism related to the defect formation and control in this system,we conducted a series of experiments aimed at controlling the point defects in Ca_(0.85)Ce_(0.15)Ag_(0.85)Sb.This strategy was realized by intentionally doping Nb,which resulted in the discovery of a series of low defect density materials Ca_(0.725+x)Nb_(0.1-x)Ce_(0.15)AgSb(0≤x≤0.05).In this work,an interesting defect controlling strategy on Zintl phases was demonstrated,which suggested the high flexibility of Ca_(1-δ)Ce_(δ)Ag_(1-δ)Sb in the optimization of thermoelectric properties.展开更多
基金the financial support from the National Natural Science Foundation of China(S.-Q.Xia:51271098,X.-T.Tao:51321091,T.-J.Zhu:11574267 and 51571177).
文摘Zintl phases with the nominal compositions Ca_(1-δ)Ce_(δ)Ag_(1-δ)Sb(RE=La,Ce,Pr,Nd,Sm;δ≈0.15)are interesting due to their unique crystal structures and potential as high temperature thermoelectrics.Their structures generally feature the LiGaGe type structure with substantial vacancies on the Ag sites.The formation of such defects can be explained by the electronic effects,with which 18 electrons are required to stabilize the CaAgSb Zintl system.Since the substitution of Ca^(2+)with RE^(3+)will lead to electron excess,the formation of Ag defects will be an intrinsic character of such compounds to maintain their electron precise nature.In this work,the material Ca_(0.85)Ce_(0.15)Ag_(0.85)Sb was selected for a detailed study on defect chemistry.In order to better understand the mechanism related to the defect formation and control in this system,we conducted a series of experiments aimed at controlling the point defects in Ca_(0.85)Ce_(0.15)Ag_(0.85)Sb.This strategy was realized by intentionally doping Nb,which resulted in the discovery of a series of low defect density materials Ca_(0.725+x)Nb_(0.1-x)Ce_(0.15)AgSb(0≤x≤0.05).In this work,an interesting defect controlling strategy on Zintl phases was demonstrated,which suggested the high flexibility of Ca_(1-δ)Ce_(δ)Ag_(1-δ)Sb in the optimization of thermoelectric properties.
