P-type thermoelectric material(Bi0.25Sb0.75)2Te3 was sintered by spark plasma sintering(SPS) process in the temperature range of 320-420 ℃. The microstructures of sintered materials were found to be well aligned,part...P-type thermoelectric material(Bi0.25Sb0.75)2Te3 was sintered by spark plasma sintering(SPS) process in the temperature range of 320-420 ℃. The microstructures of sintered materials were found to be well aligned,particularly when sintered at lower sintering temperatures. The electrical conductivity of the material became larger as the sintering temperature increased. The Seebeck coefficient showed a general decreasing tendency with an increase in sintering temperature. In terms of the power factor,the optimum sintering temperature was found to be 380 ℃ for a maximum value of around 2.6 mW/K.展开更多
The investigation of the structure and thermoelectric properties of nanostructured solid solutions (Bi, Sb)2Te3 p-type has been carried out. The samples were obtained by grinding of original compositions in a planetar...The investigation of the structure and thermoelectric properties of nanostructured solid solutions (Bi, Sb)2Te3 p-type has been carried out. The samples were obtained by grinding of original compositions in a planetary ball mill and by spark plasma sintering (SPS). Initial powder has an average particle size of 10 - 12 nm according to transmission electron microscopy, and the size of the coherent scattering region (CSR) obtained by X-ray line broadening. During sintering at Ts = 250°C - 400°C, the grain size and CSR increased, which was associated with the processes of recrystallization. The maximum of size distribution of CSR shifts to larger sizes when Ts increases so that no broadening of X-ray lines at Ts = 400°C can take place. At higher Ts, the emergence of new nanograins is observed. The formation of nanograins is conditioned by reducing of quantity of the intrinsic point defects produced in the grinding of the source materials. The study of the electrical conductivity and the Hall effect in a single crystal allows to estimate the mean free path of the holes-L in the single crystal Bi0.5Sb1.5Te3 which at room temperature is 2 - 5 nm (it is much smaller than the dimensions of CSR in the samples). The method for evaluation of L in polycrystalline samples is proposed. At room temperature, L is close to the mean free path in single crystals. Scattering parameter holes in SPS samples obtained from the temperature dependence of the Seebeck coefficient are within the measurement error equal to the parameter of the scattering of holes in a single crystal. The figure of merit ZT of SPS samples as a function of composition and sintering temperature has been investigated. Maximum ZT, equal to 1.05 at room temperature, is obtained for the composition Bi0.4Sb1.6Te3 at Ts = 500°C and a pressure of 50 MPa. The causes of an apparent increase in thermoelectric efficiency are discussed.展开更多
We report on the fabrication and characterization of multi-leg bismuth telluride (Bi2Te3) and antimony telluride (Sb2Te3) thermoelectric devices. The two materials were deposited, on top of SiO2/Si substrates, using P...We report on the fabrication and characterization of multi-leg bismuth telluride (Bi2Te3) and antimony telluride (Sb2Te3) thermoelectric devices. The two materials were deposited, on top of SiO2/Si substrates, using Pulsed Laser Deposition (PLD). The SiO2 layer was used to provide insulation between the devices and the Si wafer. Copper was used as an electrical connector and a contact for the junctions. Four devices were built, where the Bi2Te3 and Sb2Te3 were deposited at substrate temperatures of 100°C, 200°C, 300°C and 400°C. The results show that the device has a voltage sensitivity of up to 146 μV/K and temperature sensitivity of 6.8 K/mV.展开更多
To optimize the performance of a thermoelectric device for a specific application, the device should be uniquely designed for the application. Achieving an optimum design requires accurate measurements and credible an...To optimize the performance of a thermoelectric device for a specific application, the device should be uniquely designed for the application. Achieving an optimum design requires accurate measurements and credible analysis to evaluate the performance of the device and its relationship with the device parameters. To do that, we designed, fabricated, and tested four devices based on Bi2Te3 and Sb2Te3. To evaluate the accuracy of our analysis, experimental measurements were compared with the numerical simulation performed using COMSOLTM. The two sets of results were found to be in full agreement. This is a proof of the accuracy of our experimental measurements and the credibility of our simulation. The study shows that testing or simulating the devices without heat sink will lead to skewed results. This is because the junction will not hold its temperatures value, but will, instead, automatically change its value to the direction of thermal equilibrium. The study shows also that there is no reciprocity between the input and the output characteristics of the devices. Therefore, a device optimized for cooling and heating may not be automatically optimized for energy harvesting. For heating and cooling, temperature sensitivity should be optimized;while for energy harvesting, voltage sensitivity should be optimized. Using heat sink, our devices achieved a voltage sensitivity of 187.77 μV/K and a temperature sensitivity of 6.12 K/mV.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
文摘P-type thermoelectric material(Bi0.25Sb0.75)2Te3 was sintered by spark plasma sintering(SPS) process in the temperature range of 320-420 ℃. The microstructures of sintered materials were found to be well aligned,particularly when sintered at lower sintering temperatures. The electrical conductivity of the material became larger as the sintering temperature increased. The Seebeck coefficient showed a general decreasing tendency with an increase in sintering temperature. In terms of the power factor,the optimum sintering temperature was found to be 380 ℃ for a maximum value of around 2.6 mW/K.
文摘The investigation of the structure and thermoelectric properties of nanostructured solid solutions (Bi, Sb)2Te3 p-type has been carried out. The samples were obtained by grinding of original compositions in a planetary ball mill and by spark plasma sintering (SPS). Initial powder has an average particle size of 10 - 12 nm according to transmission electron microscopy, and the size of the coherent scattering region (CSR) obtained by X-ray line broadening. During sintering at Ts = 250°C - 400°C, the grain size and CSR increased, which was associated with the processes of recrystallization. The maximum of size distribution of CSR shifts to larger sizes when Ts increases so that no broadening of X-ray lines at Ts = 400°C can take place. At higher Ts, the emergence of new nanograins is observed. The formation of nanograins is conditioned by reducing of quantity of the intrinsic point defects produced in the grinding of the source materials. The study of the electrical conductivity and the Hall effect in a single crystal allows to estimate the mean free path of the holes-L in the single crystal Bi0.5Sb1.5Te3 which at room temperature is 2 - 5 nm (it is much smaller than the dimensions of CSR in the samples). The method for evaluation of L in polycrystalline samples is proposed. At room temperature, L is close to the mean free path in single crystals. Scattering parameter holes in SPS samples obtained from the temperature dependence of the Seebeck coefficient are within the measurement error equal to the parameter of the scattering of holes in a single crystal. The figure of merit ZT of SPS samples as a function of composition and sintering temperature has been investigated. Maximum ZT, equal to 1.05 at room temperature, is obtained for the composition Bi0.4Sb1.6Te3 at Ts = 500°C and a pressure of 50 MPa. The causes of an apparent increase in thermoelectric efficiency are discussed.
文摘We report on the fabrication and characterization of multi-leg bismuth telluride (Bi2Te3) and antimony telluride (Sb2Te3) thermoelectric devices. The two materials were deposited, on top of SiO2/Si substrates, using Pulsed Laser Deposition (PLD). The SiO2 layer was used to provide insulation between the devices and the Si wafer. Copper was used as an electrical connector and a contact for the junctions. Four devices were built, where the Bi2Te3 and Sb2Te3 were deposited at substrate temperatures of 100°C, 200°C, 300°C and 400°C. The results show that the device has a voltage sensitivity of up to 146 μV/K and temperature sensitivity of 6.8 K/mV.
文摘To optimize the performance of a thermoelectric device for a specific application, the device should be uniquely designed for the application. Achieving an optimum design requires accurate measurements and credible analysis to evaluate the performance of the device and its relationship with the device parameters. To do that, we designed, fabricated, and tested four devices based on Bi2Te3 and Sb2Te3. To evaluate the accuracy of our analysis, experimental measurements were compared with the numerical simulation performed using COMSOLTM. The two sets of results were found to be in full agreement. This is a proof of the accuracy of our experimental measurements and the credibility of our simulation. The study shows that testing or simulating the devices without heat sink will lead to skewed results. This is because the junction will not hold its temperatures value, but will, instead, automatically change its value to the direction of thermal equilibrium. The study shows also that there is no reciprocity between the input and the output characteristics of the devices. Therefore, a device optimized for cooling and heating may not be automatically optimized for energy harvesting. For heating and cooling, temperature sensitivity should be optimized;while for energy harvesting, voltage sensitivity should be optimized. Using heat sink, our devices achieved a voltage sensitivity of 187.77 μV/K and a temperature sensitivity of 6.12 K/mV.
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.
