Single-crystalline samples of Eu/Ba-filled Sn-based type-Ⅷ clathrate are prepared by the Ga flux method with different stoichiometric ratios. The electrical transport properties of the samples are optimized by Eu dop...Single-crystalline samples of Eu/Ba-filled Sn-based type-Ⅷ clathrate are prepared by the Ga flux method with different stoichiometric ratios. The electrical transport properties of the samples are optimized by Eu doping. Results indicate that Eu atoms tend to replace Ba atoms. With the increase of the Eu initial content, the carrier density increases and the carrier mobility decreases, which leads to an increase of the Seebeck coefficient. By contrast, the electrical conductivity decreases. Finally, the sample with Eu initial content of x = 0.75 behaves with excellent electrical properties, which shows a maximal power factor of 1.51 mW·m^-1K^-2 at 480K, and the highest ZT achieved is 0.87 near the temperature of 483K.展开更多
The superfine powders of Ln0.5 Sr0.5 CoO3 （Ln = La, Pr, Nd, Sm, Eu） were obtained by solid state reactions. The crystal structure and electrical transport properties of samples doped with different rare earth elemen...The superfine powders of Ln0.5 Sr0.5 CoO3 （Ln = La, Pr, Nd, Sm, Eu） were obtained by solid state reactions. The crystal structure and electrical transport properties of samples doped with different rare earth elements as well as the forming process of the Perovskite structure were studied. The result shows that when the temperature reaches 1200 ℃, the samples will become a steady and unitary Perovskite phase by solid state reactions. The conductive behavor at low temperature is consistent with small polaron mechanism （i. e., localized electronic carriers having a thermally activated mobility）. However, the maximum of conductivity appears at about 700 ℃, and the conductivity of La0.5Sr0.5CoO3 is the biggest in the intermediate-temperature （600 - 850 ℃ ）, so it is fit for cathode material of intermediate-temperature solid oxide fuel cells.展开更多
This study prepares a group of single crystalline β-Zn_4Sb_3 with Ge and Sn codoped by the Sn-flux method according to the nominal stoichiometric ratios of Zn_（4.4）Sb_3 Ge_xSn_3（x = 0–0.15）. The prepared samples...This study prepares a group of single crystalline β-Zn_4Sb_3 with Ge and Sn codoped by the Sn-flux method according to the nominal stoichiometric ratios of Zn_（4.4）Sb_3 Ge_xSn_3（x = 0–0.15）. The prepared samples possess a metallic luster surface with perfect appearance and large crystal sizes. The microscopic cracks or defects are invisible in the samples from the back-scattered electron image. Except for the heavily Ge-doped sample of x = 0.15, all the samples are single phase with space group R3c. The thermal analysis results show that the samples doped with Ge exhibit an excellent thermal stability.Compared with the polycrystalline Ge-substituted β-Zn_4Sb_3, the present single crystals have higher carrier mobility, and hence the electrical conductivity is improved, which reaches 7.48×10~4S·m^（-1） at room temperature for the x = 0.1 sample.The change of Ge and Sn contents does not improve the Seebeck coefficient significantly. Benefiting from the increased electrical conductivity, the sample with x = 0.075 gets the highest power factor of 1.45×10^（-3）W·m^（-1）·K^（-2） at 543 K.展开更多
Samarium-filled skutterudites SmxCo4Sb12(x=0.5,1.0) skutterudite thermoelectric(TE) materials with enhanced power factor were prepared by high-pressure and high-temperature(HPHT) technique.The microstructure propertie...Samarium-filled skutterudites SmxCo4Sb12(x=0.5,1.0) skutterudite thermoelectric(TE) materials with enhanced power factor were prepared by high-pressure and high-temperature(HPHT) technique.The microstructure properties were characterized with X-ray diffraction and scanning electron microscopy.The electrical resistivities and Seebeck coefficients of those samples were measured in the temperature range of 300-723 K,and the samples of SmxCo4Sb12 showed n-type conduction.The Seebeck coefficient in absolute valu...展开更多
Use of a flexible thermoelectric source is a feasible approach to realizing selfpowered wearable electronics and the Internet of Things.Inorganic thin films are promising candidates for fabricating flexible power supp...Use of a flexible thermoelectric source is a feasible approach to realizing selfpowered wearable electronics and the Internet of Things.Inorganic thin films are promising candidates for fabricating flexible power supply,but obtaining highthermoelectric‐performance thin films remains a big challenge.In the present work,a p‐type Bi_(x)Sb_(2−x)Te_(3) thin film is designed with a high figure of merit of 1.11 at 393 K and exceptional flexibility(less than 5%increase in resistance after 1000 cycles of bending at a radius of∼5 mm).The favorable comprehensive performance of the Bi_(x)Sb_(2−x)Te_(3) flexible thin film is due to its excellent crystallinity,optimized carrier concentration,and low elastic modulus,which have been verified by experiments and theoretical calculations.Further,a flexible device is fabricated using the prepared p‐type Bi_(x)Sb_(2−x)Te_(3) and n‐type Ag_(2)Se thin films.Consequently,an outstanding power density of∼1028μWcm^(−2)is achieved at a temperature difference of 25 K.This work extends a novel concept to the fabrication of highperformance flexible thin films and devices for wearable energy harvesting.展开更多
The samples ofLa8/9Sr1/45Na4/45MnO3 （LSNMO）/x/2（Sb2O3） were prepared by the solid-state reaction method. The electric transport properties and the temperature stabil-ity of magnetoresistance （MR） of the samples ...The samples ofLa8/9Sr1/45Na4/45MnO3 （LSNMO）/x/2（Sb2O3） were prepared by the solid-state reaction method. The electric transport properties and the temperature stabil-ity of magnetoresistance （MR） of the samples were studied through the measurements of X-ray diffraction patterns, resistivity-temperature （ρ-T） curves, mass magnetization-temperature （σ-T） curves, and magnetoresistance-temper-ature （MR-T） curves. The results indicate that the p-Tcurves of the original material LSNMO show two peaks, and the phenomenon of two peaks of ρ-T curves disappears for the composite samples, which can be explained by a competition between surface-phase resistivity induced by boundary-dependent scattering and body-phase resistivity induced by paramagnetism-ferromagnetism transition. For all the sam-ples in the low temperature range, MR increases continu-ously with the decrease of temperature, which shows a characteristic of low-field magnetoresistance. However, MR basically keeps the same in the high temperature range. The paramagnetism-ferromagnetism transition is observed in the high temperature range due to a composite between perov-skite manganite and insulator, which can enhance the tem-perature of MR appearance in the high temperature range and make it to appear near room temperature. For the sample with x = 0.12, MR remains constant at the value of 7.5 % in the temperature range of 300-260 K, which achieves a tem-perature stability of MR near room temperature. In addition,for the sample with x = 0.16, MR is above 6.8 % in the high temperature range of 318-252 K （△T = 66 K）. MR almost remains constant in this temperature range, which favors the practical application of MR.展开更多
SnSe is considered to be a promising thermoelectric material due to a high ZT value and abundant and non-toxic composition elements.However,the thermal stability is an important issue for commercial application.In par...SnSe is considered to be a promising thermoelectric material due to a high ZT value and abundant and non-toxic composition elements.However,the thermal stability is an important issue for commercial application.In particular,thermoelectric materials are in the high temperature for a long time due to the working condition.The present work investigates the thermal stability and oxidation resistance of single crystal SnSe thermoelectric materials.The scanning electron microscopy(SEM)and transmission electron microscopy(TEM)results show that the internal of SnSe crystal is not easily oxidized,while the x-ray photoelectron spectroscopy(XPS)results indicate that the surface of SnSe is slight oxidized to SnO_(2).Even if the surface is oxidized,the SnSe crystal still exhibits stable thermoelectric properties.Meanwhile,the crystallization quality of SnSe samples can be improved after the appropriate heat treatment in the air,which is in favor of the carrier mobility and can improve the electrical conduction properties of SnSe.Moreover,the decrease of defect density after heat treatment can further improve the Seebeck coefficient and electrical transport properties of SnSe.The density functional theory(DFT)calculation verifies the important role of defect on the electrical conductivity and electron configuration.In summary,appropriate temperature annealing is an effective way to improve the transmission properties of SnSe single crystal thermoelectric materials.展开更多
The perovskite samples La1-x（Sr1-yKy）xMnO3 （y = 0.0, 0.2, 04, 0.6, 0.8） were prepared by the solid-state reaction method with comparatively low sintering tem- perature and with comparatively short sintering time, ...The perovskite samples La1-x（Sr1-yKy）xMnO3 （y = 0.0, 0.2, 04, 0.6, 0.8） were prepared by the solid-state reaction method with comparatively low sintering tem- perature and with comparatively short sintering time, and the electric transport property and temperature stability of MR of this system were studied. The p-T curves show the abnormal phenomenon that with the increase of K doping amount, resistivity increases, and the insulator-metal transition temperature decreases, which is because the influence of the occupation disorder degree of A-site ions σ2 on the electric transport property of perovskite manga- nites is larger than that of the radius of A-site ions （rA）. In the temperature range below 225 K, MR increases contin- uously with the decrease of temperature, which is the characteristic of low-field magnetoresistance; in the com- paratively wide temperature range near 250 K, the MR- T curves of all the samples are comparatively fiat, and the value of MR almost does not change with temperature, which shows the temperature stability of magnetoresis- tance, and can be explained by the competition between the low-field magnetoresistance induced by spin-dependent tunneling of surface phase and the intrinsic magnetoresis- tance of grain phase. The magnetoresistance value of the sample with y = 0.8 keeps at （7.92 ±0.36） % in the very wide temperature range of 225-275 K, and this is a goodreference for the preparation of this kind of sample with practical application value in the future.展开更多
High temperature electrical and thermal transport properties,that is,electrical conductivity,Seebeck coefficient and thermal conductivity,of CdO ceramics have been investigated.Because of the good electrical propertie...High temperature electrical and thermal transport properties,that is,electrical conductivity,Seebeck coefficient and thermal conductivity,of CdO ceramics have been investigated.Because of the good electrical properties and low thermal conductivity,the dimensionless figure-of-merit ZT of the CdO ceramics reaches 0.34 at 1023 K.This value is comparable to the best reported ZT for the n-type oxide ceramic thermoelectric materials and remains as potential to be further improved by porosity controlling or nanostructuring.展开更多
The electrical and current transport properties of rapidly annealed Dy/p-GaN SBD are probed by I-V and C-V techniques. The estimated barrier heights（BH） of as-deposited and 200 ℃ annealed SBDs are 0.80 eV（I-V）/0....The electrical and current transport properties of rapidly annealed Dy/p-GaN SBD are probed by I-V and C-V techniques. The estimated barrier heights（BH） of as-deposited and 200 ℃ annealed SBDs are 0.80 eV（I-V）/0.93 eV（C-V） and 0.87 eV（I-V）/1.03 eV（C-V）. However, the BH rises to 0.99 eV（I-V）/1.18 eV（C-V）and then slightly deceases to 0.92 eV（I-V）/1.03 eV（C-V） after annealing at 300 ℃ and 400 ℃. The utmost BH is attained after annealing at 300 ℃ and thus the optimum annealing for SBD is 300 ℃. By applying Cheung＇s functions, the series resistance of the SBD is estimated. The BHs estimated by I-V, Cheung＇s and ΨS-V plot are closely matched; hence the techniques used here are consistency and validity. The interface state density of the as-deposited and annealed contacts are calculated and we found that the NSS decreases up to 300 ℃ annealing and then slightly increases after annealing at 400 ℃. Analysis indicates that ohmic and space charge limited conduction mechanisms are found at low and higher voltages in forward-bias irrespective of annealing temperatures. Our experimental results demonstrate that the Poole-Frenkel emission is leading under the reverse bias of Dy/p-GaN SBD at all annealing temperatures.展开更多
Hafnium diboride(HfB_(2))is an important metallic ceramic that works in harsh environments,due to its high strength and thermal conductivity.Although the thermal conductivity of HfB_(2) has been measured,the experimen...Hafnium diboride(HfB_(2))is an important metallic ceramic that works in harsh environments,due to its high strength and thermal conductivity.Although the thermal conductivity of HfB_(2) has been measured,the experimental results are scattered.Also,the thermal transport mechanism of HfB_(2) is not well understood.In this work,we study the thermal transport in both pristine and defective HfB_(2) from first-principles calculations.For the pristine HfB_(2),the room-temperature thermal conductivities are 175.0 and 157.7 W·m^(-1)·K^(-1)on a-and c-axes,respectively,where the contributions from electron and phonon are comparable.The Lorenz number is significantly smaller than the Sommerfeld value and shows a temperature dependence,which demonstrates that the Wiedemann-Franz law cannot be used to estimate electronic thermal conductivity.The phonon-isotope and the phonon-electron scattering are non-negligible compared to the phonon-phonon scattering.For the defective HfB_(2),the grain size effects are negligible with length scales larger than 1μm.The pore can limit thermal conductivity when its occupancy is larger than 10%.The vacancy is found to induce scattered results in experiments.The phonon thermal conductivity significantly reduces even with only 1%vacancy,while the electronic thermal conductivity is not sensitive to the vacancy.Our study provides an in-depth understanding of the thermal transport in HfB_(2),and the revealed mechanisms provide important guidance on the design of HfB_(2)-based materials.展开更多
Thermoelectric（TE）materials have been considered as a strong candidate for recovering the waste heat from industry and vehicles due to the ability to convert heat directly into electricity.Recently,multinary diamond...Thermoelectric（TE）materials have been considered as a strong candidate for recovering the waste heat from industry and vehicles due to the ability to convert heat directly into electricity.Recently,multinary diamond-like chalcogenides（MDLCs）,such as Cu In Te2,Cu2Sn Se3,Cu3Sb Se4,Cu2ZnSnSe4,etc.,are eco-friendly Pb-free TE materials with relatively large Seebeck coefficient and low thermal conductivity and have aroused intensive research as a popular theme in the TE field.In this review,we summarize the TE performance and device development of MDLCs.The features of crystalline and electronic structure are first analyzed,and then the strategies that have emerged to enhance the TE figure of merits of these materials are illustrated in detail.The final part of this review describes the advance in TE device research for MDLCs.In the outlook,the challenges and future directions are also discussed to promote the further development of MDLCs TE materials.展开更多
Lead sulfide(PbS)presents large potential in thermoelectric application due to its earth-abundant S element.However,its inferior average ZT(ZTave)value makes PbS less competitive with its analogs PbTe and PbSe.To prom...Lead sulfide(PbS)presents large potential in thermoelectric application due to its earth-abundant S element.However,its inferior average ZT(ZTave)value makes PbS less competitive with its analogs PbTe and PbSe.To promote its thermoelectric performance,this study implements strategies of continuous Se alloying and Cu interstitial doping to synergistically tune thermal and electrical transport properties in n-type PbS.First,the lattice parameter of 5.93Åin PbS is linearly expanded to 6.03Åin PbS_(0.5)Se_(0.5)with increasing Se alloying content.This expanded lattice in Se-alloyed PbS not only intensifies phonon scattering but also facilitates the formation of Cu interstitials.Based on the PbS_(0.6)Se_(0.4)content with the minimal lattice thermal conductivity,Cu interstitials are introduced to improve the electron density,thus boosting the peak power factor,from 3.88μW cm^(−1)K^(−2)in PbS_(0.6)Se_(0.4)to 20.58μW cm^(−1)K^(−2)in PbS0.6Se0.4−1%Cu.Meanwhile,the lattice thermal conductivity in PbS_(0.6)Se_(0.4)−x%Cu(x=0-2)is further suppressed due to the strong strain field caused by Cu interstitials.Finally,with the lowered thermal conductivity and high electrical transport properties,a peak ZT~1.1 and ZTave~0.82 can be achieved in PbS_(0.6)Se_(0.4)−1%Cu at 300–773K,which outperforms previously reported n-type PbS.展开更多
The layered transition metal dichalcogenides(TMDs)have raised considerable interest in the past decades for both fundamental physics and low-dimensional nanodevice applications.Recently,intriguing phenomena of Ising s...The layered transition metal dichalcogenides(TMDs)have raised considerable interest in the past decades for both fundamental physics and low-dimensional nanodevice applications.Recently,intriguing phenomena of Ising superconductivity and quantum metallic state have been reported in two-dimensional(2D)4Ha-TaSe2 nanodevices.Here,we report the magnetic field induced superconductor–metal transition(SMT)in mechanical exfoliated 4Ha-TaSe2 nanodevices with thickness down to 2.5 nm.We observe the quantum Griffiths singularity(QGS)of SMT in thin 4Ha-TaSe2 nanodevices by performing ultralow temperature transport measurements and activated scaling analysis.With increasing the thickness of TaSe2 nanodevice to 10.6 nm,the signature of magnetoresistance crossing region can hardly be detected,revealing the thickness dependence of SMT.In this procedure,the disorder strength plays a dominant role.This work enriches the platform for studying QGS and may stimulate further investigations on the correlation between different novel quantum phenomena in the same 2D superconducting system.展开更多
High-throughput(HTP)experiments play key roles in accelerating the discovery of advanced materials,but the HTP preparation and characterization,especially for bulk samples,are extremely difficult.In this work,we devel...High-throughput(HTP)experiments play key roles in accelerating the discovery of advanced materials,but the HTP preparation and characterization,especially for bulk samples,are extremely difficult.In this work,we developed a novel and general strategy for HTP screening of high-performance bulk thermoelectric materials.The performed fullchain HTP experiments cover rapid synthesis of the bulk sample with quasi-continuous composition,microarea phase identification and structure analysis,and measurement of the spatial distribution of the sample composition,electrical and thermal transport properties.According to our experiments,bulk Bi_(2-x)Sb_(x)Te_(3)(x=1-2)and Bi_(2)Te_(3-x)Se_(x)(x=0-1.5)samples with quasi-continuous compositions have been rapidly fabricated by this HTP method.The target thermoelectric materials with the best Sb/Bi and Te/Se ratios are successfully screened out based on subsequent HTP characterization results,demonstrating that this HTP technique is effective in speeding up the exploration of novel high-performance thermoelectric materials.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No 51262032
文摘Single-crystalline samples of Eu/Ba-filled Sn-based type-Ⅷ clathrate are prepared by the Ga flux method with different stoichiometric ratios. The electrical transport properties of the samples are optimized by Eu doping. Results indicate that Eu atoms tend to replace Ba atoms. With the increase of the Eu initial content, the carrier density increases and the carrier mobility decreases, which leads to an increase of the Seebeck coefficient. By contrast, the electrical conductivity decreases. Finally, the sample with Eu initial content of x = 0.75 behaves with excellent electrical properties, which shows a maximal power factor of 1.51 mW·m^-1K^-2 at 480K, and the highest ZT achieved is 0.87 near the temperature of 483K.
文摘The superfine powders of Ln0.5 Sr0.5 CoO3 （Ln = La, Pr, Nd, Sm, Eu） were obtained by solid state reactions. The crystal structure and electrical transport properties of samples doped with different rare earth elements as well as the forming process of the Perovskite structure were studied. The result shows that when the temperature reaches 1200 ℃, the samples will become a steady and unitary Perovskite phase by solid state reactions. The conductive behavor at low temperature is consistent with small polaron mechanism （i. e., localized electronic carriers having a thermally activated mobility）. However, the maximum of conductivity appears at about 700 ℃, and the conductivity of La0.5Sr0.5CoO3 is the biggest in the intermediate-temperature （600 - 850 ℃ ）, so it is fit for cathode material of intermediate-temperature solid oxide fuel cells.
基金Project supported by the National Natural Science Foundation of China(Grant No.51262032)
文摘This study prepares a group of single crystalline β-Zn_4Sb_3 with Ge and Sn codoped by the Sn-flux method according to the nominal stoichiometric ratios of Zn_（4.4）Sb_3 Ge_xSn_3（x = 0–0.15）. The prepared samples possess a metallic luster surface with perfect appearance and large crystal sizes. The microscopic cracks or defects are invisible in the samples from the back-scattered electron image. Except for the heavily Ge-doped sample of x = 0.15, all the samples are single phase with space group R3c. The thermal analysis results show that the samples doped with Ge exhibit an excellent thermal stability.Compared with the polycrystalline Ge-substituted β-Zn_4Sb_3, the present single crystals have higher carrier mobility, and hence the electrical conductivity is improved, which reaches 7.48×10~4S·m^（-1） at room temperature for the x = 0.1 sample.The change of Ge and Sn contents does not improve the Seebeck coefficient significantly. Benefiting from the increased electrical conductivity, the sample with x = 0.075 gets the highest power factor of 1.45×10^（-3）W·m^（-1）·K^（-2） at 543 K.
基金supported by the National Natural Science Foundation of China (50731006,50801030)
文摘Samarium-filled skutterudites SmxCo4Sb12(x=0.5,1.0) skutterudite thermoelectric(TE) materials with enhanced power factor were prepared by high-pressure and high-temperature(HPHT) technique.The microstructure properties were characterized with X-ray diffraction and scanning electron microscopy.The electrical resistivities and Seebeck coefficients of those samples were measured in the temperature range of 300-723 K,and the samples of SmxCo4Sb12 showed n-type conduction.The Seebeck coefficient in absolute valu...
基金National Natural Science Foundation of China,Grant/Award Number:62274112Guangdong Basic and Applied Basic Research Foundation,Grant/Award Number:2022A1515010929Science and Technology Plan project of Shenzhen,Grant/Award Numbers:JCYJ20220531103601003,20220810154601001。
文摘Use of a flexible thermoelectric source is a feasible approach to realizing selfpowered wearable electronics and the Internet of Things.Inorganic thin films are promising candidates for fabricating flexible power supply,but obtaining highthermoelectric‐performance thin films remains a big challenge.In the present work,a p‐type Bi_(x)Sb_(2−x)Te_(3) thin film is designed with a high figure of merit of 1.11 at 393 K and exceptional flexibility(less than 5%increase in resistance after 1000 cycles of bending at a radius of∼5 mm).The favorable comprehensive performance of the Bi_(x)Sb_(2−x)Te_(3) flexible thin film is due to its excellent crystallinity,optimized carrier concentration,and low elastic modulus,which have been verified by experiments and theoretical calculations.Further,a flexible device is fabricated using the prepared p‐type Bi_(x)Sb_(2−x)Te_(3) and n‐type Ag_(2)Se thin films.Consequently,an outstanding power density of∼1028μWcm^(−2)is achieved at a temperature difference of 25 K.This work extends a novel concept to the fabrication of highperformance flexible thin films and devices for wearable energy harvesting.
基金financially supported by the National Natural Science Foundation of China(No.19934003)the Natural Science Foundation of the Education Bureau of Anhui Province,China(Nos.KJ2011A259 and KJ2012Z404)+1 种基金Anhui Key Laboratory of Spintronics and Nano-materials Program(Nos.2010YKF01 and 2010YKF04)the Professors’and Doctors’ Research Startup Foundation of Suzhou University(Nos.2011jb01 and 2010jb02)
文摘The samples ofLa8/9Sr1/45Na4/45MnO3 （LSNMO）/x/2（Sb2O3） were prepared by the solid-state reaction method. The electric transport properties and the temperature stabil-ity of magnetoresistance （MR） of the samples were studied through the measurements of X-ray diffraction patterns, resistivity-temperature （ρ-T） curves, mass magnetization-temperature （σ-T） curves, and magnetoresistance-temper-ature （MR-T） curves. The results indicate that the p-Tcurves of the original material LSNMO show two peaks, and the phenomenon of two peaks of ρ-T curves disappears for the composite samples, which can be explained by a competition between surface-phase resistivity induced by boundary-dependent scattering and body-phase resistivity induced by paramagnetism-ferromagnetism transition. For all the sam-ples in the low temperature range, MR increases continu-ously with the decrease of temperature, which shows a characteristic of low-field magnetoresistance. However, MR basically keeps the same in the high temperature range. The paramagnetism-ferromagnetism transition is observed in the high temperature range due to a composite between perov-skite manganite and insulator, which can enhance the tem-perature of MR appearance in the high temperature range and make it to appear near room temperature. For the sample with x = 0.12, MR remains constant at the value of 7.5 % in the temperature range of 300-260 K, which achieves a tem-perature stability of MR near room temperature. In addition,for the sample with x = 0.16, MR is above 6.8 % in the high temperature range of 318-252 K （△T = 66 K）. MR almost remains constant in this temperature range, which favors the practical application of MR.
基金Project supported by the National Natural Science Foundation of China(Grant No.61864012)
文摘SnSe is considered to be a promising thermoelectric material due to a high ZT value and abundant and non-toxic composition elements.However,the thermal stability is an important issue for commercial application.In particular,thermoelectric materials are in the high temperature for a long time due to the working condition.The present work investigates the thermal stability and oxidation resistance of single crystal SnSe thermoelectric materials.The scanning electron microscopy(SEM)and transmission electron microscopy(TEM)results show that the internal of SnSe crystal is not easily oxidized,while the x-ray photoelectron spectroscopy(XPS)results indicate that the surface of SnSe is slight oxidized to SnO_(2).Even if the surface is oxidized,the SnSe crystal still exhibits stable thermoelectric properties.Meanwhile,the crystallization quality of SnSe samples can be improved after the appropriate heat treatment in the air,which is in favor of the carrier mobility and can improve the electrical conduction properties of SnSe.Moreover,the decrease of defect density after heat treatment can further improve the Seebeck coefficient and electrical transport properties of SnSe.The density functional theory(DFT)calculation verifies the important role of defect on the electrical conductivity and electron configuration.In summary,appropriate temperature annealing is an effective way to improve the transmission properties of SnSe single crystal thermoelectric materials.
基金financially supported by the National Natural Science Foundation of China (No. 19934003)the Key Program of Natural Science Foundation of Anhui Province (Nos. KJ2011A259 and KJ2013A245)+1 种基金the Program of Professors and Doctors' Research Startup Foundation of Suzhou College (Nos. 2011jb01 and 2011jb02)the Program of Cultivating Base of Anhui Key Laboratory of Spintronics and Nano-materials Research (No. 2012YKF09)
文摘The perovskite samples La1-x（Sr1-yKy）xMnO3 （y = 0.0, 0.2, 04, 0.6, 0.8） were prepared by the solid-state reaction method with comparatively low sintering tem- perature and with comparatively short sintering time, and the electric transport property and temperature stability of MR of this system were studied. The p-T curves show the abnormal phenomenon that with the increase of K doping amount, resistivity increases, and the insulator-metal transition temperature decreases, which is because the influence of the occupation disorder degree of A-site ions σ2 on the electric transport property of perovskite manga- nites is larger than that of the radius of A-site ions （rA）. In the temperature range below 225 K, MR increases contin- uously with the decrease of temperature, which is the characteristic of low-field magnetoresistance; in the com- paratively wide temperature range near 250 K, the MR- T curves of all the samples are comparatively fiat, and the value of MR almost does not change with temperature, which shows the temperature stability of magnetoresis- tance, and can be explained by the competition between the low-field magnetoresistance induced by spin-dependent tunneling of surface phase and the intrinsic magnetoresis- tance of grain phase. The magnetoresistance value of the sample with y = 0.8 keeps at （7.92 ±0.36） % in the very wide temperature range of 225-275 K, and this is a goodreference for the preparation of this kind of sample with practical application value in the future.
基金supported by the Natural Science Foundation for Distinguished Young Scholars of Hebei Province(Grant No.A2013201249)the National Natural Science Foundation of China(Grant No.51372064)
文摘High temperature electrical and thermal transport properties,that is,electrical conductivity,Seebeck coefficient and thermal conductivity,of CdO ceramics have been investigated.Because of the good electrical properties and low thermal conductivity,the dimensionless figure-of-merit ZT of the CdO ceramics reaches 0.34 at 1023 K.This value is comparable to the best reported ZT for the n-type oxide ceramic thermoelectric materials and remains as potential to be further improved by porosity controlling or nanostructuring.
文摘The electrical and current transport properties of rapidly annealed Dy/p-GaN SBD are probed by I-V and C-V techniques. The estimated barrier heights（BH） of as-deposited and 200 ℃ annealed SBDs are 0.80 eV（I-V）/0.93 eV（C-V） and 0.87 eV（I-V）/1.03 eV（C-V）. However, the BH rises to 0.99 eV（I-V）/1.18 eV（C-V）and then slightly deceases to 0.92 eV（I-V）/1.03 eV（C-V） after annealing at 300 ℃ and 400 ℃. The utmost BH is attained after annealing at 300 ℃ and thus the optimum annealing for SBD is 300 ℃. By applying Cheung＇s functions, the series resistance of the SBD is estimated. The BHs estimated by I-V, Cheung＇s and ΨS-V plot are closely matched; hence the techniques used here are consistency and validity. The interface state density of the as-deposited and annealed contacts are calculated and we found that the NSS decreases up to 300 ℃ annealing and then slightly increases after annealing at 400 ℃. Analysis indicates that ohmic and space charge limited conduction mechanisms are found at low and higher voltages in forward-bias irrespective of annealing temperatures. Our experimental results demonstrate that the Poole-Frenkel emission is leading under the reverse bias of Dy/p-GaN SBD at all annealing temperatures.
基金financially supported by the National Natural Science Foundation of China (NSFC) (No.52122606)support by Shanghai Municipal Natural Science Foundation (No.22YF1400100)the Fundamental Research Funds for the Central Universities (No.2232022D-22)。
文摘Hafnium diboride(HfB_(2))is an important metallic ceramic that works in harsh environments,due to its high strength and thermal conductivity.Although the thermal conductivity of HfB_(2) has been measured,the experimental results are scattered.Also,the thermal transport mechanism of HfB_(2) is not well understood.In this work,we study the thermal transport in both pristine and defective HfB_(2) from first-principles calculations.For the pristine HfB_(2),the room-temperature thermal conductivities are 175.0 and 157.7 W·m^(-1)·K^(-1)on a-and c-axes,respectively,where the contributions from electron and phonon are comparable.The Lorenz number is significantly smaller than the Sommerfeld value and shows a temperature dependence,which demonstrates that the Wiedemann-Franz law cannot be used to estimate electronic thermal conductivity.The phonon-isotope and the phonon-electron scattering are non-negligible compared to the phonon-phonon scattering.For the defective HfB_(2),the grain size effects are negligible with length scales larger than 1μm.The pore can limit thermal conductivity when its occupancy is larger than 10%.The vacancy is found to induce scattered results in experiments.The phonon thermal conductivity significantly reduces even with only 1%vacancy,while the electronic thermal conductivity is not sensitive to the vacancy.Our study provides an in-depth understanding of the thermal transport in HfB_(2),and the revealed mechanisms provide important guidance on the design of HfB_(2)-based materials.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51372064 and 61704044)the Key Project of the Natural Science Foundation of Hebei Province,China(Grant No.E2017201227)
文摘Thermoelectric（TE）materials have been considered as a strong candidate for recovering the waste heat from industry and vehicles due to the ability to convert heat directly into electricity.Recently,multinary diamond-like chalcogenides（MDLCs）,such as Cu In Te2,Cu2Sn Se3,Cu3Sb Se4,Cu2ZnSnSe4,etc.,are eco-friendly Pb-free TE materials with relatively large Seebeck coefficient and low thermal conductivity and have aroused intensive research as a popular theme in the TE field.In this review,we summarize the TE performance and device development of MDLCs.The features of crystalline and electronic structure are first analyzed,and then the strategies that have emerged to enhance the TE figure of merits of these materials are illustrated in detail.The final part of this review describes the advance in TE device research for MDLCs.In the outlook,the challenges and future directions are also discussed to promote the further development of MDLCs TE materials.
基金National Science Fund for Distinguished Young Scholars,Grant/Award Number:51925101National Natural Science Foundation of China,Grant/Award Number:52172236+1 种基金Fundamental Research Funds for the Central Universities,Grant/Award Number:xtr042021007Top Young Talents Programme of Xi'an Jiaotong University。
文摘Lead sulfide(PbS)presents large potential in thermoelectric application due to its earth-abundant S element.However,its inferior average ZT(ZTave)value makes PbS less competitive with its analogs PbTe and PbSe.To promote its thermoelectric performance,this study implements strategies of continuous Se alloying and Cu interstitial doping to synergistically tune thermal and electrical transport properties in n-type PbS.First,the lattice parameter of 5.93Åin PbS is linearly expanded to 6.03Åin PbS_(0.5)Se_(0.5)with increasing Se alloying content.This expanded lattice in Se-alloyed PbS not only intensifies phonon scattering but also facilitates the formation of Cu interstitials.Based on the PbS_(0.6)Se_(0.4)content with the minimal lattice thermal conductivity,Cu interstitials are introduced to improve the electron density,thus boosting the peak power factor,from 3.88μW cm^(−1)K^(−2)in PbS_(0.6)Se_(0.4)to 20.58μW cm^(−1)K^(−2)in PbS0.6Se0.4−1%Cu.Meanwhile,the lattice thermal conductivity in PbS_(0.6)Se_(0.4)−x%Cu(x=0-2)is further suppressed due to the strong strain field caused by Cu interstitials.Finally,with the lowered thermal conductivity and high electrical transport properties,a peak ZT~1.1 and ZTave~0.82 can be achieved in PbS_(0.6)Se_(0.4)−1%Cu at 300–773K,which outperforms previously reported n-type PbS.
基金the National Natural Science Foundation of China(Nos.11888101,11974430,and 12174442)the National Key R&D Program of China(Nos.2018YFA0305600 and 2022YFA1403103)+3 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB28000000)the Innovation Program for Quantum Science and Technology(No.2021ZD0302400)Young Elite Scientists Sponsorship Program by BAST(No.BYESS2023452)the Fundamental Research Funds for the Central Universities,and the Research Funds of Renmin University of China(No.22XNKJ20).
文摘The layered transition metal dichalcogenides(TMDs)have raised considerable interest in the past decades for both fundamental physics and low-dimensional nanodevice applications.Recently,intriguing phenomena of Ising superconductivity and quantum metallic state have been reported in two-dimensional(2D)4Ha-TaSe2 nanodevices.Here,we report the magnetic field induced superconductor–metal transition(SMT)in mechanical exfoliated 4Ha-TaSe2 nanodevices with thickness down to 2.5 nm.We observe the quantum Griffiths singularity(QGS)of SMT in thin 4Ha-TaSe2 nanodevices by performing ultralow temperature transport measurements and activated scaling analysis.With increasing the thickness of TaSe2 nanodevice to 10.6 nm,the signature of magnetoresistance crossing region can hardly be detected,revealing the thickness dependence of SMT.In this procedure,the disorder strength plays a dominant role.This work enriches the platform for studying QGS and may stimulate further investigations on the correlation between different novel quantum phenomena in the same 2D superconducting system.
基金supported by the National Key Research and Development Program of China(2018YFB0703600 and 2018YFA0702100)the National Natural Science Foundation of China(51772186,51632005 and 51371194)。
文摘High-throughput(HTP)experiments play key roles in accelerating the discovery of advanced materials,but the HTP preparation and characterization,especially for bulk samples,are extremely difficult.In this work,we developed a novel and general strategy for HTP screening of high-performance bulk thermoelectric materials.The performed fullchain HTP experiments cover rapid synthesis of the bulk sample with quasi-continuous composition,microarea phase identification and structure analysis,and measurement of the spatial distribution of the sample composition,electrical and thermal transport properties.According to our experiments,bulk Bi_(2-x)Sb_(x)Te_(3)(x=1-2)and Bi_(2)Te_(3-x)Se_(x)(x=0-1.5)samples with quasi-continuous compositions have been rapidly fabricated by this HTP method.The target thermoelectric materials with the best Sb/Bi and Te/Se ratios are successfully screened out based on subsequent HTP characterization results,demonstrating that this HTP technique is effective in speeding up the exploration of novel high-performance thermoelectric materials.
