Rahidul Hasan - Academia.edu (original) (raw)
Papers by Rahidul Hasan
Korean Journal of Metals and Materials
Herein we report the optimized processing conditions of hot extrusion for fabricating an n-type B... more Herein we report the optimized processing conditions of hot extrusion for fabricating an n-type Bi2Te2.7Se0.3 thermoelectric compound, with high electronic transport properties as well as improved mechanical reliability. We fabricated a Bi2Te2.7Se0.3 extrudate that was 3.8 mm in diameter and 700 mm in length by controlling the processing parameters of temperature and pressure. A 3-point bending strength of over 70 MPa, which is 7 times higher that of the commercial zone melting ingot, was obtained in the samples prepared at 460 oC temperature under 6–6.5 MPa pressure. The samples benefitted from the formation of a highly-dense microstructure (relative density > 98%). It is noted that the electronic transport properties (electrical conductivity and Seebeck coefficient) could be manipulated by controlling the applied pressure of hot extrusion at 460 oC, mainly due to the change in the characteristics of the 00l crystal orientation, which originated from grain rotation and rearrange...
Advanced Energy and Sustainability Research, 2022
Double half‐Heuslers comprising two aliovalent half‐Heuslers are promising candidates for thermoe... more Double half‐Heuslers comprising two aliovalent half‐Heuslers are promising candidates for thermoelectric materials because of their intrinsically low lattice thermal conductivity; however, poor electronic transport properties need to be overcome. Herein, the effects of Sn doping on the electronic and thermal transport properties of p‐type Ti2FeNiSb2 to enhance the thermoelectric performance via the compositional tuning route are investigated. The power factor is significantly improved owing to the synergetic effect of the increase in the density‐of‐states effective mass and the carrier concentration. In addition, the lattice thermal conductivity is slightly reduced, benefitted from intensified phonon scattering due to lattice disordering by Sn substitution at the Sb‐site. A peak figure of merit (zT) of ≈0.28 is obtained at 973 K in Ti2FeNiSb1.8Sn0.2, which is almost twice higher than that of the pristine Ti2FeNiSb2.
Inorganic Chemistry Frontiers
The excessed Ni will embed full-hesuler TiNi2Sb nanoprecipitates into the matrix, which can impro... more The excessed Ni will embed full-hesuler TiNi2Sb nanoprecipitates into the matrix, which can improve the thermoelectric performance by scattering low-energy carriers and phonons.
Journal of Ceramic Processing Research, 2020
Thermoelectric and transport properties of FeVSb1-xSnx (0.015<x<0.055) alloys were ... more Thermoelectric and transport properties of FeVSb1-xSnx (0.015<x<0.055) alloys were studied with respect to types of vials (zirconia and stainless steel), Sn contents and temperature. The results were compared with the previously studied samples synthesized by using stainless-vial. All the designated compositions in current work were prepared via a mechanical alloying process using a zirconia vial. Vacuum hot pressing was conducted to consolidate the mechanically alloyed powders. F43m symmetry was being confirmed from the Rietveld refinement pattern. The phase transitions during the milling process and vacuum hot processing were investigated and the results exhibited near single half-Heusler phases with a minor portion of the second phase within the matrix. The Second phase might play a role to reduce thermal conductivity. Electrical conductivity exhibited semi-metallic behavior in all the temperature range. Carrier concentrations are found to be decreased with the increasing Sn contents and the FeVSb0.955Sn0.045 specimen showed the ZT max of 0.23 at 757 K.
Journal of Ceramic Processing Research, 2019
Journal of Electronic Materials, 2019
Se-doped half-Heusler compositions, FeVSb 1Àx Se x (0.03 £ x £ 0.15), were fabricated by mechanic... more Se-doped half-Heusler compositions, FeVSb 1Àx Se x (0.03 £ x £ 0.15), were fabricated by mechanical alloying followed by vacuum hot pressing. The goal of this synthesis was to explore the effect of Se doping on the thermoelectric and transport properties of FeVSb system. A near single half-Heusler phase was found to form; however, a second phase of FeSb 2 couldn't be avoided in this process. N-type conduction was confirmed and Se acted as a donor for the FeVSb system. Lattice thermal conductivity also considerably decreased after Se doping. The absolute value of Seebeck coefficient is increased to a maximum of 126 lVK À1 at 956 K for x = 0.12, which may help to increase the figure of merit (ZT) of the FeVSb system. The figure of merit is improved by Se doping, and the improvement is possibly owing to the combined effect of fine grain structure, increased effective mass and phonon scattering at the grain boundaries. A maximum ZT of 0.27 was achieved for FeVSb 0.88 Se 0.12 at 847 K.
Electronic Materials Letters, 2018
The thermoelectric and transport properties of Ti-doped FeVSb half-Heusler alloys were studied in... more The thermoelectric and transport properties of Ti-doped FeVSb half-Heusler alloys were studied in this study. FeV 1−x Ti x Sb (0.1 < x < 0.5) half-Heusler alloys were synthesized by mechanical alloying process and subsequent vacuum hot pressing. After vacuum hot pressing, a near singe phase with a small fraction of second phase was obtained in this experiment. Investigation of microstructure revealed that both grain and particle sizes were decreased on doping which would influence on thermal conductivity. No foreign elements pick up from the vial was seen during milling process. Thermoelectric properties were investigated as a function of temperature and doping level. The absolute value of Seebeck coefficient showed transition from negative to positive with increasing doping concentrations (x ≥ 0.3). Electrical conductivity, Seebeck coefficient and power factor increased with the increasing amount of Ti contents. The lattice thermal conductivity decreased considerably, possibly due to the mass disorder and grain boundary scattering. All of these turned out to increase in power factor significantly. As a result, the thermoelectric figure of merit increased comprehensively with Ti doping for this experiment, resulting in maximum thermoelectric figure of merit for FeV 0.7 Ti 0.3 Sb at 658 K.
Transactions on Electrical and Electronic Materials, 2018
Mn-doped FeVSb half-Heusler alloys were synthesized via a mechanical alloying process and consoli... more Mn-doped FeVSb half-Heusler alloys were synthesized via a mechanical alloying process and consolidated by vacuum hot pressing. The microstructure and phase transformation of all the samples were examined by XRD and SEM. Thermoelectric properties such as the Seebeck coefficient, electrical conductivity and thermal conductivity were investigated in the moderate temperature range from 300 to 973 K. The negative value of both the Seebeck and Hall coefficients confirms the presence of n-type conductivity. The Seebeck coefficient increased with an increasing doping amount, but the electrical conductivity decreased, owing to decreasing carrier concentration. The thermal conductivity found in this experiment was quite high, possibly due to bipolar diffusion of the electronic band energy. The maximum value of the dimensionless figure of merit was achieved using a relatively high value of the Seebeck coefficient and a significantly higher value of electrical conductivity. The maximum value of ZT was observed for Fe 0.996 Mn 0.004 VSb at 468 K.
Transactions on Electrical and Electronic Materials, 2018
In the current work, we tried to investigate and compare the thermoelectric performance of the Fe... more In the current work, we tried to investigate and compare the thermoelectric performance of the FeVSb 1−x Sn x (x = 0.0-0.05) half-Heusler system. The elemental mixture was formulated and subjected to mechanical alloying, and subsequently consolidated using vacuum hot pressing. X-ray diffractometry analysis was used to observe phase transition during the process, and scanning electron microscopy was utilized for microstructure analysis. After vacuum hot pressing, a near single phase of FeVSb 1−x Sn x (x = 0.0-0.05) was observed with small portions of second phases. The vacuum hot-pressed samples were analyzed to study the thermoelectric properties as a function of temperature up to 980 K. The n-type conduction was confirmed from Seebeck and Hall coefficients in the test range. In addition, the electrical conductivity showed combined conduction behavior in the test range, while the thermal conductivities showed abnormal behavior. Mass fluctuation scattering and changing in carrier concentration might have taken place during doping. The Seebeck coefficient and electrical conductivity of the system also decreased after doping. Dimensionless figure of merit values were calculated and compared with the results of analogue studies. The maximum ZT value was obtained for x = 0.01 at 553 K.
Journal of Materials Research and Technology, 2021
BieTe-based alloys are potential candidates for use in thermoelectric (TE) modules for lowmid-tem... more BieTe-based alloys are potential candidates for use in thermoelectric (TE) modules for lowmid-temperature energy harvesting. However, n-type BieTeeSe alloys are inferior to their p-type counterparts in terms of TE performance. It has been found that doping Cu atoms into n-type BieTeeSe alloys is effective in improving the TE properties; however, different studies have reported contrasting roles of Cu dopants in the transport properties of BieTe eSe alloys. This is attributed to the complex doping behaviors of Cu atoms. In this study, it is demonstrated that employing an appropriate fabrication technique can enable more Cu dopants to be directed to specific atomic sites than others. As part of the study, two n-type polycrystalline Cu 0.01 Bi 1.99 Te 2.7 Se 0.3 bulk samples are respectively fabricated via meltspinning followed by spark plasma sintering, and via ball-milling followed by spark plasma sintering. The majority of Cu dopants in the melt-spun sample are suspected to exist in between Te 1 eTe 1 atomic layers (van der Waals gap), given the elongated c-axis, increased Hall carrier concentration, and improved non-degenerate mobility (intercalated Cu generates one electron and acts as an electric connector). Resultantly, a~30% enhancement in the TE figure-of-merit (~0.92 at 360e400 K) is achieved in the melt-spun sample, relative to the ball-milled sample, wherein Cu atoms substitute Bi atoms.
Korean Journal of Metals and Materials
Herein we report the optimized processing conditions of hot extrusion for fabricating an n-type B... more Herein we report the optimized processing conditions of hot extrusion for fabricating an n-type Bi2Te2.7Se0.3 thermoelectric compound, with high electronic transport properties as well as improved mechanical reliability. We fabricated a Bi2Te2.7Se0.3 extrudate that was 3.8 mm in diameter and 700 mm in length by controlling the processing parameters of temperature and pressure. A 3-point bending strength of over 70 MPa, which is 7 times higher that of the commercial zone melting ingot, was obtained in the samples prepared at 460 oC temperature under 6–6.5 MPa pressure. The samples benefitted from the formation of a highly-dense microstructure (relative density > 98%). It is noted that the electronic transport properties (electrical conductivity and Seebeck coefficient) could be manipulated by controlling the applied pressure of hot extrusion at 460 oC, mainly due to the change in the characteristics of the 00l crystal orientation, which originated from grain rotation and rearrange...
Advanced Energy and Sustainability Research, 2022
Double half‐Heuslers comprising two aliovalent half‐Heuslers are promising candidates for thermoe... more Double half‐Heuslers comprising two aliovalent half‐Heuslers are promising candidates for thermoelectric materials because of their intrinsically low lattice thermal conductivity; however, poor electronic transport properties need to be overcome. Herein, the effects of Sn doping on the electronic and thermal transport properties of p‐type Ti2FeNiSb2 to enhance the thermoelectric performance via the compositional tuning route are investigated. The power factor is significantly improved owing to the synergetic effect of the increase in the density‐of‐states effective mass and the carrier concentration. In addition, the lattice thermal conductivity is slightly reduced, benefitted from intensified phonon scattering due to lattice disordering by Sn substitution at the Sb‐site. A peak figure of merit (zT) of ≈0.28 is obtained at 973 K in Ti2FeNiSb1.8Sn0.2, which is almost twice higher than that of the pristine Ti2FeNiSb2.
Inorganic Chemistry Frontiers
The excessed Ni will embed full-hesuler TiNi2Sb nanoprecipitates into the matrix, which can impro... more The excessed Ni will embed full-hesuler TiNi2Sb nanoprecipitates into the matrix, which can improve the thermoelectric performance by scattering low-energy carriers and phonons.
Journal of Ceramic Processing Research, 2020
Thermoelectric and transport properties of FeVSb1-xSnx (0.015<x<0.055) alloys were ... more Thermoelectric and transport properties of FeVSb1-xSnx (0.015<x<0.055) alloys were studied with respect to types of vials (zirconia and stainless steel), Sn contents and temperature. The results were compared with the previously studied samples synthesized by using stainless-vial. All the designated compositions in current work were prepared via a mechanical alloying process using a zirconia vial. Vacuum hot pressing was conducted to consolidate the mechanically alloyed powders. F43m symmetry was being confirmed from the Rietveld refinement pattern. The phase transitions during the milling process and vacuum hot processing were investigated and the results exhibited near single half-Heusler phases with a minor portion of the second phase within the matrix. The Second phase might play a role to reduce thermal conductivity. Electrical conductivity exhibited semi-metallic behavior in all the temperature range. Carrier concentrations are found to be decreased with the increasing Sn contents and the FeVSb0.955Sn0.045 specimen showed the ZT max of 0.23 at 757 K.
Journal of Ceramic Processing Research, 2019
Journal of Electronic Materials, 2019
Se-doped half-Heusler compositions, FeVSb 1Àx Se x (0.03 £ x £ 0.15), were fabricated by mechanic... more Se-doped half-Heusler compositions, FeVSb 1Àx Se x (0.03 £ x £ 0.15), were fabricated by mechanical alloying followed by vacuum hot pressing. The goal of this synthesis was to explore the effect of Se doping on the thermoelectric and transport properties of FeVSb system. A near single half-Heusler phase was found to form; however, a second phase of FeSb 2 couldn't be avoided in this process. N-type conduction was confirmed and Se acted as a donor for the FeVSb system. Lattice thermal conductivity also considerably decreased after Se doping. The absolute value of Seebeck coefficient is increased to a maximum of 126 lVK À1 at 956 K for x = 0.12, which may help to increase the figure of merit (ZT) of the FeVSb system. The figure of merit is improved by Se doping, and the improvement is possibly owing to the combined effect of fine grain structure, increased effective mass and phonon scattering at the grain boundaries. A maximum ZT of 0.27 was achieved for FeVSb 0.88 Se 0.12 at 847 K.
Electronic Materials Letters, 2018
The thermoelectric and transport properties of Ti-doped FeVSb half-Heusler alloys were studied in... more The thermoelectric and transport properties of Ti-doped FeVSb half-Heusler alloys were studied in this study. FeV 1−x Ti x Sb (0.1 < x < 0.5) half-Heusler alloys were synthesized by mechanical alloying process and subsequent vacuum hot pressing. After vacuum hot pressing, a near singe phase with a small fraction of second phase was obtained in this experiment. Investigation of microstructure revealed that both grain and particle sizes were decreased on doping which would influence on thermal conductivity. No foreign elements pick up from the vial was seen during milling process. Thermoelectric properties were investigated as a function of temperature and doping level. The absolute value of Seebeck coefficient showed transition from negative to positive with increasing doping concentrations (x ≥ 0.3). Electrical conductivity, Seebeck coefficient and power factor increased with the increasing amount of Ti contents. The lattice thermal conductivity decreased considerably, possibly due to the mass disorder and grain boundary scattering. All of these turned out to increase in power factor significantly. As a result, the thermoelectric figure of merit increased comprehensively with Ti doping for this experiment, resulting in maximum thermoelectric figure of merit for FeV 0.7 Ti 0.3 Sb at 658 K.
Transactions on Electrical and Electronic Materials, 2018
Mn-doped FeVSb half-Heusler alloys were synthesized via a mechanical alloying process and consoli... more Mn-doped FeVSb half-Heusler alloys were synthesized via a mechanical alloying process and consolidated by vacuum hot pressing. The microstructure and phase transformation of all the samples were examined by XRD and SEM. Thermoelectric properties such as the Seebeck coefficient, electrical conductivity and thermal conductivity were investigated in the moderate temperature range from 300 to 973 K. The negative value of both the Seebeck and Hall coefficients confirms the presence of n-type conductivity. The Seebeck coefficient increased with an increasing doping amount, but the electrical conductivity decreased, owing to decreasing carrier concentration. The thermal conductivity found in this experiment was quite high, possibly due to bipolar diffusion of the electronic band energy. The maximum value of the dimensionless figure of merit was achieved using a relatively high value of the Seebeck coefficient and a significantly higher value of electrical conductivity. The maximum value of ZT was observed for Fe 0.996 Mn 0.004 VSb at 468 K.
Transactions on Electrical and Electronic Materials, 2018
In the current work, we tried to investigate and compare the thermoelectric performance of the Fe... more In the current work, we tried to investigate and compare the thermoelectric performance of the FeVSb 1−x Sn x (x = 0.0-0.05) half-Heusler system. The elemental mixture was formulated and subjected to mechanical alloying, and subsequently consolidated using vacuum hot pressing. X-ray diffractometry analysis was used to observe phase transition during the process, and scanning electron microscopy was utilized for microstructure analysis. After vacuum hot pressing, a near single phase of FeVSb 1−x Sn x (x = 0.0-0.05) was observed with small portions of second phases. The vacuum hot-pressed samples were analyzed to study the thermoelectric properties as a function of temperature up to 980 K. The n-type conduction was confirmed from Seebeck and Hall coefficients in the test range. In addition, the electrical conductivity showed combined conduction behavior in the test range, while the thermal conductivities showed abnormal behavior. Mass fluctuation scattering and changing in carrier concentration might have taken place during doping. The Seebeck coefficient and electrical conductivity of the system also decreased after doping. Dimensionless figure of merit values were calculated and compared with the results of analogue studies. The maximum ZT value was obtained for x = 0.01 at 553 K.
Journal of Materials Research and Technology, 2021
BieTe-based alloys are potential candidates for use in thermoelectric (TE) modules for lowmid-tem... more BieTe-based alloys are potential candidates for use in thermoelectric (TE) modules for lowmid-temperature energy harvesting. However, n-type BieTeeSe alloys are inferior to their p-type counterparts in terms of TE performance. It has been found that doping Cu atoms into n-type BieTeeSe alloys is effective in improving the TE properties; however, different studies have reported contrasting roles of Cu dopants in the transport properties of BieTe eSe alloys. This is attributed to the complex doping behaviors of Cu atoms. In this study, it is demonstrated that employing an appropriate fabrication technique can enable more Cu dopants to be directed to specific atomic sites than others. As part of the study, two n-type polycrystalline Cu 0.01 Bi 1.99 Te 2.7 Se 0.3 bulk samples are respectively fabricated via meltspinning followed by spark plasma sintering, and via ball-milling followed by spark plasma sintering. The majority of Cu dopants in the melt-spun sample are suspected to exist in between Te 1 eTe 1 atomic layers (van der Waals gap), given the elongated c-axis, increased Hall carrier concentration, and improved non-degenerate mobility (intercalated Cu generates one electron and acts as an electric connector). Resultantly, a~30% enhancement in the TE figure-of-merit (~0.92 at 360e400 K) is achieved in the melt-spun sample, relative to the ball-milled sample, wherein Cu atoms substitute Bi atoms.