Power Factor Values Research Articles

Thermoelectric characteristics of Co3(BO3)2 and NaF-substituted Bi2Sr2Co2Oy prepared via a sol-gel route

Abstract The discovery of thermoelectric cobaltites initiated a systematic exploration of these materials for potential applications in thermoelectric generators, which convert waste heat into electricity. This technology may contribute to addressing the current energy crisis. Among the cobaltites studied, p-type Bi2Sr2Co2Oy is a promising thermoelectric material. However, a significant drawback of cobaltites is their low thermoelectric conversion efficiency. To improve thermoelectric performance, it is essential to optimize synthesis techniques, enhance microstructure, and incorporate various dopants and additives, etc. In this work, reference, Co3(BO3)2 and NaF-substituted, as well as Co3(BO3)2/NaF co-substituted Bi2Sr2Co2Oy ceramics were prepared using the sol–gel method. We examined the microstructure and evaluated the power factor (PF) and figure of merit (ZT) through measurements of electrical resistivity (ρ), Seebeck coefficient (S), and thermal conductivity (k). The introduction of substituents reduced the resistivity of Bi2Sr2Co2Oy, leading to improvements in both PF and ZT values. The highest PF and ZT values were achieved for Co3(BO3)2–substituted Bi2Sr2Co2Oy. The incorporation of Co3(BO3)2 significantly increased the material’s grain size and density. The PF enhanced from 0.124 mW/(m⋅K2) at 973 K for the reference sample to 0.228 mW/(m⋅K2) for the Co3(BO3)2 –substituted sample, while ZT raised from 0.054 to 0.072 at 573 K.

Thermoelectric Properties of Antiperovskite X<sub>3</sub>SiO (X = Sr and Ba)

Thermoelectric materials are useful for various application in daily life. Their application such as sensors, generators and electronic components, making thermoelectric materials widely studied. Antiperovskite compounds that can have semiconducting behaviour is probable candidate for thermoelectric materials. In this article, thermoelectric properties of anti-perovskite X3SiO (X = Sr and Ba) were investigated using density functional theory (DFT) method and Boltzmann Transport Equations (BTE). Electronic properties such as band structure, partial density of states were computed using the generalized gradient approximation with Perdew-Burke-Ernzerhof (GGA-PBE) functional in CASTEP code. The thermoelectric properties such as Seebeck coefficient, electrical conductivity, and power factor are calculated using BoltzTraP code that utilised BTE. The calculated band structures of Ba3SiO and Sr3SiO show that these compounds having semiconductor behaviour with direct band gap of 0.44 and 0.43 eV respectively at Γ-Γ k-point. It was found that Ba3SiO is a better candidate for thermoelectric materials due to its higher Seebeck coefficient (-4.90 10-4 V/K) at room temperature compared to calculated Seebeck coefficient (-5.84 10-4 V/K) of Sr3SiO. The power factor value of Ba3SiO which is 2.96 x 10-4 W/mK2 is also higher compared to power factor of Sr3SiO at 7.12 x 10-7 W/mK2 at room temperature.

Nanoarchitectonics of High-Performance and Flexible n-Type Organic-Inorganic Composite Thermoelectric Fibers for Wearable Electronics.

Since most conductive polymers are p-type, developing high-performance n-type organic-inorganic composite thermoelectric (TE) fibers is a great challenge. Herein, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)-coated Ag2Te nanowires (PC-Ag2Te NWs) were prepared by a liquid-phase reaction using PEDOT:PSS-coated Te nanowires (PC-Te NWs) as templates, and the PEDOT:PSS/PC-Ag2Te NWs composite fibers were then prepared by wet spinning. As the content of PC-Ag2Te NWs increases, the composite fiber changes from p-type to n-type. The PEDOT: PSS coating greatly improves the dispersibility of Ag2Te NWs in the PEDOT: PSS matrix, resulting in an ultrahigh content of 87.5 wt % of PC-Ag2Te NWs in the composite fibers, which exhibited a Seebeck coefficient of -61.3 μV K-1 and a power factor of 65.3 μW m-1 K-2. The power factor value is higher than those of previously reported n-type composite TE fibers. Contrary to the estimated thermal conductivity in other reports, in this work, the thermal conductivity of the composite fibers was measured via a transient photoelectrothermal (TPET) technique. In addition, the composite fiber has good tensile properties and mechanical strength, elongating at a break of 47.37% and a tensile stress of 6.59 MPa. For an application demonstration, a self-powered temperature sensor was assembled, which can utilize the vertical temperature difference between the human body and the environment and respond quickly to a small temperature difference.

Power factor correction: performance comparison of an existing microcontroller-based system and a neuro-fuzzy system

An existing microcontroller-based power factor correction system has been able to improve the overall conversion of electrical power into a useful work of a highly industrial load. However, more improvements are still desired to get the existing power factor value close to 1 as much as practically possible. With the current microcontroller-based power factor correction system, microcontroller has to be replaced often due to power fluctuation and a low-quality power available. The microcontroller requires ordering for new replacement as it is not reprogrammable to meet the new operational demands. Artificial intelligence tools, neural network and fuzzy logic are considered. Neuro-fuzzy system approach is settled for as an alternative to microcontroller-based power factor correction system. Neuro-fuzzy system is able to learn through training, testing, and validation processes and controls the automatic switching of the capacitor banks to adequately compensate for the lagging loads. Results obtained were compared to the existing microcontroller power factor correction system. Neuro-fuzzy system shows better performance over microcontroller-based system. The neuro-fuzzy system automatically adjusts itself to suit the present operational requirement to always have a power factor result closer to 1 as compared with that of a microcontroller-based system which does not give room for reprogramming making it static to a larger extent in its operational duties.

Highly Deformable Van der Waals Chalcogenides with Superior Thermoelectric Performance from Interpretable Machine Learning.

Van der Waals (vdW) chalcogenide-based flexible thermoelectric devices hold great promise for wearable electronics. However, intrinsic vdW chalcogenides that combine high flexibility with superior thermoelectric figures of merit (ZT) remain extremely rare. Consequently, there is an urgent need to develop methods capable of high-throughput screening to identify potential vdW chalcogenides with both robust flexibility and favorable ZT value. In this study, over 1000 vdW chalcogenides are high-throughput screened for their flexibility and ZT values. Flexibility is evaluated using the previously developed deformability factor, while ZT values are predicted using a machine learning model. Several candidates with large deformability and high ZT are successfully identified. Among these, NbSe2Br2 emerges as the top-performing material. Further first-principles calculations reveal that it achieves a maximum ZT value of 1.35 at 1000 K, the highest reported so far among flexible inorganic thermoelectric materials. Its power factor value of 8.1 µW cm-1K-2 at 300 K also surpasses most organic and inorganic flexible thermoelectric materials. The high ZTmax is mainly contributed by the extremely low thermal conductivity and the high Seebeck coefficient along the out-of-plane direction at high temperatures. The study offers new material options for the development and application of flexible thermoelectric devices based on layered chalcogenides.

Toward Enhancing the Thermoelectric Properties of Bi2Te3 and Sb2Te3 Alloys by Co-Evaporation of Bi2Te3:Bi and Sb2Te3:Te.

In this work, we developed nanostructured Bi2Te3 and Sb2Te3 thin films by thermal co-evaporation of their alloys with corresponding pure elements (Bi, Sb, and Te). The films were fabricated on borosilicate glass at different substrate temperatures and deposition rates. At 300 °C, enhanced thermoelectric performance was demonstrated for n-type Bi2Te3:Bi and p-type Sb2Te3:Te, with Seebeck coefficients of 195 µV K-1 and 178 μV K-1, along with electrical conductivities of 4.6 × 104 (Ω m)-1 and 6.9 × 104 (Ω m)-1, resulting in maximum power factor values of 1.75 mW K-2 m-1 and 2.19 mW K-2 m-1, respectively. These values are found to be higher than some reported works in the literature, highlighting the advantage of not introducing additional elements to the system (such as extra doping, which induces complexity to the system). The structural properties, film morphology, and chemical composition of the optimized films were investigated using X-ray diffraction (XRD) and scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM-EDS). The films were found to be polycrystalline with preferred (0 0 6) and (0 1 5) orientations for Bi2Te3 and Sb2Te3 films, respectively, and stable rhombohedral phases. Additionally, a ring-shaped p-n thermoelectric device for localized heating/cooling was developed and a temperature difference of ~7 °C between the hot and cold zones was obtained using 4.8 mA of current (J = 0.068 mA/mm2).

Enhancing the Thermoelectric Performance of Bi2O2Se Ceramics via Multi-Element Doping

Bi2O2Se, as the n-type counterpart of p-type BiCuSeO, has garnered considerable attention. The lower carrier concentration leads to reduced electrical conductivity, prompting extensive research efforts aimed at enhancing its electrical performance. This study prepared Bi2−3x(CeTiSn)xO2Se (x = 0, 0.02, 0.03, and 0.04) ceramics using a combination of high-energy ball milling and cold isostatic pressing techniques. Results demonstrated that the incorporation of multiple elements led to an increase in the carrier concentration within the Bi2O2Se system, thereby improving electrical conductivity. The electrical conductivity increased from 5.1 S/cm for Bi2O2Se to 154.1 S/cm for Bi1.88(CeTiSn)0.04O2Se at 323 K. Furthermore, the maximum power factor value of Bi1.88(CeTiSn)0.04O2Se was 112 μW m−1 K−2 at 763 K. Doping led to a slight increase in thermal conductivity. The figure of merit ZTmax value of Bi1.88(CeTiSn)0.04O2Se was ~0.16, marking a significant enhancement of about 1.45 times compared to that of the pure sample (~0.11).

Coexistence of Kondo effect and non trivial Berry phase in Gd doped Bi2Se3: an ARPES and magneto-transport study

Abstract The presence of magnetic impurities in topological insulators can disrupt their time reversal symmetry and lead to the emergence of an energy gap. This study delves into the energy band structure and the Kondo effect through the introduction of Gadolinium (Gd) magnetic perturbations (at levels of x = 0.1 , 0.16 ) into a pure Bi2Se3 single crystal. In the case of the Bi1.9Gd0.1Se3 (5%) single crystal, the Kondo effect becomes observable at temperatures below 50 K. However, the unaltered parent and Bi1.84Gd0.16Se3 (8%) exhibit typical metallic behavior. The pure sample displays the highest magnetoresistance (MR) of around 225% and demonstrates quantum oscillations driven by a nontrivial berry phase. The sample doped with 5% Gd undergoes a transition from negative MR to positive MR due to a presence of mixed magnetic state resulting from the opening of a gap at the Dirac point. This gap opening is confirmed through angle-resolved photoemission spectroscopy (ARPES) measurements. The comparison of the parameters obtained from the SdH and ARPES measurements, the reduction in the k F values in the magnetotransport measurements is likely due to the band bending induced by the Schottky barrier. Thermoelectric properties are assessed across all prepared samples. The undoped sample displays the highest Seebeck coefficient and power factor values of − 398.02 μ V K − 1 and 6.83 mW mK − 2 , respectively, at room temperature. These values are notably high for thermoelectric applications at room temperature.

Helical dislocation-driven plasticity and flexible high-performance thermoelectric generator in α-Mg3Bi2 single crystals

Inorganic plastic semiconductors play a crucial role in the realm of flexible electronics. In this study, we present a cost-effective plastic thermoelectric semimetal magnesium bismuthide (α-Mg3Bi2), exhibiting remarkable thermoelectric performance. Bulk single-crystalline α-Mg3Bi2 exhibits considerable plastic deformation at room temperature, allowing for the fabrication of intricate shapes such as the letters “SUSTECH” and a flexible chain. Transmission electron microscopy, time-of-flight neutron diffraction, and chemical bonding theoretic analyses elucidate that the plasticity of α-Mg3Bi2 stems from the helical dislocation-driven interlayer slip, small-sized Mg atoms induced weak interlayer Mg-Bi bonds, and low modulus of intralayer Mg2Bi22- networks. Moreover, we achieve a power factor value of up to 26.2 µW cm-1 K-2 along the c-axis at room temperature in an n-type α-Mg3Bi2 crystal. Our out-of-plane flexible thermoelectric generator exhibit a normalized power density of 8.1 μW cm-2 K-2 with a temperature difference of 7.3 K. This high-performance plastic thermoelectric semimetal promises to advance the field of flexible and deformable electronics.

A Zn-doped Sb2Te3 flexible thin film with decoupled Seebeck coefficient and electrical conductivity via band engineering.

Sb2Te3-based flexible thin films can be utilized in the fabrication of self-powered wearable devices due to their huge potential in thermoelectric performance. Although doping can significantly enhance the power factor value, the process of identifying suitable dopants is typically accompanied by numerous repeating experiments. Herein, we introduce Zn doping into thermally diffused p-type Sb2Te3 flexible thin films with a candidate dopant validated using the first-principles calculations. Subsequent experiments further corroborated the successful introduction of a Zn dopant and the improvement of thermoelectric performance. Specifically, p-type doping and the increase in the calculated effective mass can significantly increase the Seebeck coefficient, achieving the decoupling of the Seebeck coefficient and electrical conductivity in Sb2Te3 flexible thin films. An outstanding power factor of ∼22.93 μW cm-1 K-2 at room temperature can be obtained in the 0.58% Zn doped Sb2Te3 sample with significant flexibility. The subsequent fabrication of a flexible thermoelectric generator provides the maximum output voltage and output power of ∼53.0 mV and ∼1100 nW with a temperature difference of 40 K, respectively, pointing out the huge potential of Zn-doped Sb2Te3 materials for thermoelectric applications in self-powered wearable devices.

Improved thermoelectric efficiency of Sb2Si2Te6 through yttrium-induced nanocompositing.

Sb2Si2Te6 is a promising 2D material for medium-temperature thermoelectric applications, with the thermoelectric figure of merit zT approaching 1 at 823 K. However, its widespread use has been limited by relatively low power factor values. In this study, we successfully enhanced the performance of Sb2Si2Te6 by introducing Yttrium nanocomposites. This modification fine-tuned the carrier concentration and electrical conductivity, and increased the power factor up to 946 μW K-1 at 570 K. Jonker plot analysis revealed that increased carrier concentration did not affect the intrinsic electronic properties. SEM and TEM analyses revealed that Y nano-compositing introduced secondary phases, reducing the lattice thermal conductivity to values close to simulated ones using the Debye-Callaway model. Sb1.98Y0.02Si2Te6 exhibited the highest zT of 1.49 at 773 K due to the ultralow lattice thermal conductivity of 0.29 W m-1 K-1 and a moderate power factor of 858 μW K-1 at the same temperature. The single parabolic band (SPB) model suggests that with further optimization of the Fermi level and additional reduction in lattice thermal conductivity, the zT value could potentially increase to 1.55. These results demonstrate the potential of Y nanocompositing for enhancing Sb2Si2Te6 as an efficient medium-temperature thermoelectric material.

Unveiling the synthesis mechanisms of (Bi,Sb,Sn)-Te and observation of the n-type to p-type semiconducting transition in Sb-Bi2Te3 nanostructured chalcogenides derived via an aqueous-based reflux method.

A systematic study of a surfactant-assisted, aqueous-based, low-temperature chemical method for the synthesis of (Bi,Sb,Sn)-Te nanostructures was carried out. A detailed understanding of the chemistry involved in the reaction mechanism and decomposition of ethylenediaminetetraacetic acid was proposed for different precursors of Bi, Sb and Sn, and the possibilities for the aqueous-based, low-temperature synthesis of phase pure Bi2Te3, SnTe, and Sb2Te3 was demonstrated. The reaction mechanism revealed that the aqueous-based reflux reaction is suitable for the synthesis of Bi2Te3, unsuitable for the synthesis of SnTe, and suitable for the partial formation of Sb2Te3. Hot-pressed Sb-doped Bi2Te3 samples exhibited an n- to p-type semiconducting transition with variations in temperature and Sb dopant concentration. A significant improvement in Seebeck coefficient and power factor values of 215.12 μV K-1 and 7.1 μW m-1 K-2, respectively, was observed at 465 K for the 5% Sb-doped Bi2Te3 nanostructures. This work focuses primarily on the reaction mechanism of Bi-, Sb- and Sn-based tellurides in an aqueous medium, providing further possibilities in the field of chalcogenide nanostructures for thermoelectric applications.

Barrier Energy Engineering Enables Efficient Carrier Transport of Single-Walled Carbon Nanotube-Small Organic Molecules Hybrid Thermoelectrics.

Understanding the inherent charge carrier transport mechanism within carbon nanotube-organic hybrid thermoelectric (TE) materials is crucial for enhancing their TE performance. Although various carbon nanotube-organic hybrid TE materials have been developed, the influence of the barrier energy on the TE transport mechanism within these hybrids remains elusive. Our study focuses on the engineering of barrier energy between single-walled carbon nanotubes (SWCNTs) and small organic molecules (SOMs) by modulating the mesomeric effects of terminal functional groups on T-shaped SOMs. The minimization of barrier energy in an SWCNTs-BTBIN hybrid to 0.04 eV resulted in a semiconducting-dominant transport character, facilitating the energy filtering of SWCNTs-BTBIN. Consequently, SWCNTs-BTBIN achieved a higher Seebeck coefficient (65 μV K-1) than other hybrids (39-54 μV K-1) having steeper barrier energies (0.30 and 0.19 eV), enabling the highest power factor (798 μW m-1 K-2) and ZT value up to 0.035 at room temperature among SWCNTs-BTBI hybrid series. A TE module consisting of SWCNTs-BTBIN incorporating five-leg TE elements produced an output power exceeding 0.82 μW, suggesting that integrating barrier energy engineering with analyses of TE transport mechanisms can significantly advance the design of high-performance nanocarbon-based organic hybrid TEs.

Effects of Ti and Sn Substitutions on Magnetic and Transport Properties of the TiFe2Sn Full Heusler Compound

The synthesis of polycrystalline TiFe2Sn samples by a route including arc melting and spark plasma sintering with Hf, Y, and In substitutions at the Ti and Sn sites is investigated. For a reduced amount of substitution, around 2 at%, the samples are single phase, while for increased amounts, secondary phases segregate. As is characteristic of these compounds, the Fe-Ti atomic disorder generates a weak ferromagnetic ordering, which is also influenced by the type of substitutional atoms and the secondary phases in the samples with a higher Hf content. The Seebeck coefficient values show an increase for Ti0.98Hf0.02Fe2Sn and for samples with an adjusted Sn content, resulting in slightly increased power factor values. These values reach a maximum for Ti0.98Hf0.02Fe2Sn at approximately 300 K and for TiFe2Sn1.05 at approximately 325 K, namely, 2.69 × 10⁻4 Wm−1K−2 and 2.52 × 10⁻4 Wm−1K−2, respectively. The thermal conductivity of all the samples with substitutions increases with respect to the pristine sample. The highest figure of merit value of 0.016 is also obtained for Ti0.98Hf0.02Fe2Sn at 325 K.

Assessment of Wind Energy in the Ali Al-Gharbi Region

Assessment of wind resources is an important issue in the wind industry. This study aims to assess wind energy in southern Iraq, especially in the Ali Al-Gharbi region. It includes field data for the wind speed at two altitudes (30 and 50m) in 2017, using the Weibull Distribution, wind power density and wind energy density equations. The probability density distribution of mean wind speed and daily, monthly, and seasonal wind speeds were calculated. The monthly mean wind power density and wind energy density at heights (30 and 50m) were estimated. The suitable wind turbine in this study area was the Unison U50. The capacity factor was assessed. The results showed a northwesterly prevailing wind speed direction in the study area. Mean wind speed increases during day hours and decreases during night hours throughout the four seasons. The highest monthly mean wind speed is in May and June. The highest seasonal mean wind speed is in spring and summer, while the lowest is in winter and autumn. The highest monthly mean of wind power density and wind energy density were in June, while the lowest values were in February. The highest monthly values of wind power, wind energy, and capacity factor were (5851.11kW, 4212802.15kW.h, 78%) respectively, while the lowest monthly values were (1080.43kW, 777913.34kW.h, 14%), respectively.

Enhanced thermoelectric properties of bismuth telluride via Ultra-Low thermal conductivity BOSC compound addition

Enhanced thermoelectric properties of bismuth telluride via Ultra-Low thermal conductivity BOSC compound addition

Investigation of optical and thermoelectric characteristics of novel zintl-phase alloys CaZn2X2 (X = P, As, Sb) for green energy applications

Abstract This study examines the photovoltaic and thermoelectric response of calcium-based novel Zintl-phase alloys CaZn2X2 (X = P, As, Sb). The structural, optoelectronics, and transport features of Zintl CaZn2X2 (X = P, As, Sb) compounds have been analyzed using the full potential linearized augmented plane wave (FPLAPW) technique. Investigations on formation energy and phonon dispersion have confirmed the formation and dynamical stabilities. These compounds exhibit a semiconductor behavior, as their predicted bandgap values: 1.76 eV for CaZn2P2, 1.14 eV for CaZn2As2, and 0.32 eV for CaZn2Sb2. By investigating the optical properties, we have discovered their potential applicability in optoelectronic and photovoltaic devices, as evidenced by the optical response of these phases. The traditional Boltzmann transport theory has assessed transport characteristics against temperature and chemical potential. Significantly higher values of the Seebeck coefficient are achieved at room and elevated temperatures. Moreover, the power factor demonstrates a linear relationship with rising temperature. The remarkable optoelectronic properties and exceptional power factor values suggest that these materials are suitable for deployment in photovoltaic and transport devices.

Design and finite element analysis of a high‐performance surface‐permanent magnet synchronous reluctance machine with optimised robustness towards demagnetisation

AbstractThe aim of this paper is to design and Finite Element Analysis (FEA) of a novel rotor topology for a permanent magnet synchronous reluctance machine. According to the advantages and drawbacks of the PMSyncRM and the SPMSM, a conventional PMSyncRM rotor design combined with sur‐face‐mounted magnets is introduced as the SPMSyncRM. The surface‐PM arc size is investigated, so that it is considered as multiplication of an integer coefficient and the angle between two adjacent slots of the stator. The analysis involves simulation of the electromagnetic characteristics and the numerical model of each structure using finite element method. Each E‐Magnetic character is calculated for a better understanding of the benefits of the SPMSyncRM. Applying 2D FEA, the optimised surface‐PM arc size is calculated and the static and dynamic operational behaviour of the SPMSyncRM is simulated. Moreover, short circuit analysis is performed to study the demagnetisation of magnets. All results are reported comparatively considering a conventional PMSyncRM, so that the proposed SPM‐SyncRM topology presents high torque‐power density, lower values of cogging torque, higher values of power factor and efficiency, better static and dynamic performance, and robustness towards demagnetisation.

First principle study of electronic, optoelectronic, and thermoelectric properties of zintl phase alloys BaAg2X2 (X = S, Se, Te) for renewable energy

First principle study of electronic, optoelectronic, and thermoelectric properties of zintl phase alloys BaAg2X2 (X = S, Se, Te) for renewable energy

Inclusion of 2D nanosheets on ZnSb matrix as a unique approach to improve its thermoelectric performance

Inclusion of 2D nanosheets on ZnSb matrix as a unique approach to improve its thermoelectric performance