The thermoelectric materials have been considered as a potential candidate for the new power generation technology based on their reversible heat and electricity conversion.Lead telluride(Pb Te) is regarded as an ex...The thermoelectric materials have been considered as a potential candidate for the new power generation technology based on their reversible heat and electricity conversion.Lead telluride(Pb Te) is regarded as an excellent mid-temperature thermoelectric material due to its suitable intrinsic thermoelectric properties.So tremendous efforts have been done to improve the thermoelectric performance of Pb Te,and figures of merit,zT 〉 2.0,have been reported.Main strategies for optimizing the thermoelectric performance have been focused as the main line of this review.The band engineering and phonon scattering engineering as two main effective strategies are systemically summarized here.The band engineering,like band convergence,resonant levels,and band flatting have been addressed in improving the power factor.Additionally,phonon scattering engineerings,such as atomic-scale,nano-scale,meso-scale,and multi-scale phonon scatterings have been applied to reduce the thermal conductivity.Besides,some successful synergistic effects based on band engineerings and phonon scatterings are illustrated as a simultaneous way to optimize both the power factor and thermal conductivity.Summarizing the above three main parts,we point out that the synergistic effects should be effectively exploited,and these may further boost the thermoelectric performance of Pb Te alloys and can be extended to other thermoelectric materials.展开更多
With the fabrication of high-performance thermoelectric(TE)materials,developments are being made in enhanc-ing the figure of merit,zT,of TE materials.Liquid-like binary copper selenide(Cu_(2) Se)chalcogenides recently...With the fabrication of high-performance thermoelectric(TE)materials,developments are being made in enhanc-ing the figure of merit,zT,of TE materials.Liquid-like binary copper selenide(Cu_(2) Se)chalcogenides recently gained significant recognition because of their anomalous but fascinating electrical and thermal transport perfor-mances.In this study,a facile synthesis technique was adopted in fabricating Cu_(2) Se nanoparticles using a rapid microwave-assisted hydrothermal route at different reaction times.The results were compared with those of the Cu_(2) Se solid-state(SS)sample synthesized using the traditional melting and annealing technique.X-ray diffrac-tion patterns revealed successful synthesis of nanoparticles and a phase transition from orthorhombic𝛼-phase and cubic𝛽-phase to a single orthorhombic structure after hot-pressing.Scanning electron microscopic images revealed that although the grain sizes of the nanoparticle(NP)bulk samples increased with the reaction time of the microwave hydrothermal process,the grain sizes were significantly smaller than that of the SS sample.Additionally,NP bulk samples exhibited plenty of nano-grains and pores that are absent in the SS sample.The size and distribution of the grains and pores were measured to study their effects on the transport of carriers and phonons.The NP30 sample exhibited the highest power factor of 983.3μW K−2 m at 673 K among the NP samples,exhibiting intermediate values of resistivity and Seebeck coefficient that are close to those of the SS sample.Moreover,the NP samples exhibited appreciably lower thermal conductivity than the SS sample that is attributed to strengthened phonon scattering.The minimum thermal conductivity of the NP05 sample,0.78 WK−1 m−1 at 348 K,is 1.7 times lower than that of the SS sample.Finally,a maximum zT of 0.56 at 673 K,being approximately 1.3 times higher than that of the SS sample owing to the optimized thermal conductivity,was achieved for the NP30 sample.This value is comparable to or higher than that reported for Cu_(2) Se synthesized using the traditional SS method.Investigations revealed that the proposed microwave hydrothermal synthesis technique is a facile,rapid,and reliable method that results in Cu_(2) Se alloys with excellent TE performance.展开更多
基金Project supported by the National Basic Research Program of China(Grant No.2013CB632506)the National Natural Science Foundation of China(Grant Nos.51501105,51672159,and 51611540342)+4 种基金the Young Scholars Program of Shandong University(Grant No.2015WLJH21)the China Postdoctoral Science Foundation(Grant Nos.2015M580588 and 2016T90631)the Postdoctoral Innovation Foundation of Shandong Province,China(Grant No.201603027)the Fundamental Research Funds of Shandong University(Grant No.2015TB019)the Foundation of the State Key Laboratory of Metastable Materials Science and Technology(Grant No.201703)
文摘The thermoelectric materials have been considered as a potential candidate for the new power generation technology based on their reversible heat and electricity conversion.Lead telluride(Pb Te) is regarded as an excellent mid-temperature thermoelectric material due to its suitable intrinsic thermoelectric properties.So tremendous efforts have been done to improve the thermoelectric performance of Pb Te,and figures of merit,zT 〉 2.0,have been reported.Main strategies for optimizing the thermoelectric performance have been focused as the main line of this review.The band engineering and phonon scattering engineering as two main effective strategies are systemically summarized here.The band engineering,like band convergence,resonant levels,and band flatting have been addressed in improving the power factor.Additionally,phonon scattering engineerings,such as atomic-scale,nano-scale,meso-scale,and multi-scale phonon scatterings have been applied to reduce the thermal conductivity.Besides,some successful synergistic effects based on band engineerings and phonon scatterings are illustrated as a simultaneous way to optimize both the power factor and thermal conductivity.Summarizing the above three main parts,we point out that the synergistic effects should be effectively exploited,and these may further boost the thermoelectric performance of Pb Te alloys and can be extended to other thermoelectric materials.
基金supported financially by the National Key R&D Pro-gram of China(2017YFE0195200)the Natural Science Fund of China(under grant nos.51871134,52171216,and 52111530034)+1 种基金the Science Fund of Shandong Province(under grant no.ZR2019MEM007)the Qilu Young Scholar Program of Shandong University.
文摘With the fabrication of high-performance thermoelectric(TE)materials,developments are being made in enhanc-ing the figure of merit,zT,of TE materials.Liquid-like binary copper selenide(Cu_(2) Se)chalcogenides recently gained significant recognition because of their anomalous but fascinating electrical and thermal transport perfor-mances.In this study,a facile synthesis technique was adopted in fabricating Cu_(2) Se nanoparticles using a rapid microwave-assisted hydrothermal route at different reaction times.The results were compared with those of the Cu_(2) Se solid-state(SS)sample synthesized using the traditional melting and annealing technique.X-ray diffrac-tion patterns revealed successful synthesis of nanoparticles and a phase transition from orthorhombic𝛼-phase and cubic𝛽-phase to a single orthorhombic structure after hot-pressing.Scanning electron microscopic images revealed that although the grain sizes of the nanoparticle(NP)bulk samples increased with the reaction time of the microwave hydrothermal process,the grain sizes were significantly smaller than that of the SS sample.Additionally,NP bulk samples exhibited plenty of nano-grains and pores that are absent in the SS sample.The size and distribution of the grains and pores were measured to study their effects on the transport of carriers and phonons.The NP30 sample exhibited the highest power factor of 983.3μW K−2 m at 673 K among the NP samples,exhibiting intermediate values of resistivity and Seebeck coefficient that are close to those of the SS sample.Moreover,the NP samples exhibited appreciably lower thermal conductivity than the SS sample that is attributed to strengthened phonon scattering.The minimum thermal conductivity of the NP05 sample,0.78 WK−1 m−1 at 348 K,is 1.7 times lower than that of the SS sample.Finally,a maximum zT of 0.56 at 673 K,being approximately 1.3 times higher than that of the SS sample owing to the optimized thermal conductivity,was achieved for the NP30 sample.This value is comparable to or higher than that reported for Cu_(2) Se synthesized using the traditional SS method.Investigations revealed that the proposed microwave hydrothermal synthesis technique is a facile,rapid,and reliable method that results in Cu_(2) Se alloys with excellent TE performance.