Previous research on the ternary Ti-Fe-Sb system has revealed that stoichiometric TiFeSb cannot exist as a stable compound,whereas a single-phase TiFe_(1.33)Sb alloy with the half-Heusler-like structure has been synth...Previous research on the ternary Ti-Fe-Sb system has revealed that stoichiometric TiFeSb cannot exist as a stable compound,whereas a single-phase TiFe_(1.33)Sb alloy with the half-Heusler-like structure has been synthesized by adding excessive Fe.In this work,we report that TiFeSb can also be stabilized by filling additional Cu to the vacant 4d site of the half-Heusler lattice.Our experiments indicate that the TiFe-Cu_(x)Sb(x=0-0.25)samples exhibit a p-type conduction with extremely high carrier concentration((0.5-2.5)×10^(22)cm^(-3)),while these samples attain very large Seebeck coefficients,over 100 mV/K in the whole measured temperature range for the samples with x=0.15-0.25.In addition,a logarithmic divergence of the temperature-dependent specific heat capacity(CP/T)is observed at low temperatures,implying the strange-metal behavior of TiFeCu_(x)Sb samples.The partial filling of the vacant 4d site results in significantly reduced lattice thermal conductivity,leading to the low total thermal conductivity of 2.8 W·m^(-1)·K^(-1)at 823 K for the TiFeCu_(0.20)Sb sample.Consequently,a dimensionless figure of merit zT of 0.54 at 923 K is realized for TiFeCu_(0.20)Sb,demonstrating that promising thermoelectric materials with intriguing physical properties can be discovered in the composition gap of half-and full-Heusler alloys.展开更多
基金support of the National Key Research and Development Program of China(No.2018YFA0702100)National Natural Science Foundation of China(No.52272226 and 52072234).
文摘Previous research on the ternary Ti-Fe-Sb system has revealed that stoichiometric TiFeSb cannot exist as a stable compound,whereas a single-phase TiFe_(1.33)Sb alloy with the half-Heusler-like structure has been synthesized by adding excessive Fe.In this work,we report that TiFeSb can also be stabilized by filling additional Cu to the vacant 4d site of the half-Heusler lattice.Our experiments indicate that the TiFe-Cu_(x)Sb(x=0-0.25)samples exhibit a p-type conduction with extremely high carrier concentration((0.5-2.5)×10^(22)cm^(-3)),while these samples attain very large Seebeck coefficients,over 100 mV/K in the whole measured temperature range for the samples with x=0.15-0.25.In addition,a logarithmic divergence of the temperature-dependent specific heat capacity(CP/T)is observed at low temperatures,implying the strange-metal behavior of TiFeCu_(x)Sb samples.The partial filling of the vacant 4d site results in significantly reduced lattice thermal conductivity,leading to the low total thermal conductivity of 2.8 W·m^(-1)·K^(-1)at 823 K for the TiFeCu_(0.20)Sb sample.Consequently,a dimensionless figure of merit zT of 0.54 at 923 K is realized for TiFeCu_(0.20)Sb,demonstrating that promising thermoelectric materials with intriguing physical properties can be discovered in the composition gap of half-and full-Heusler alloys.
基金supported by the National Key Research and Development Program of China(2018YFA0702100)the National Natural Science Foundation of China(52272226,U21A2054,and 52072234).
