Thermoelectric Phase Research Articles

Fluctuation effects in superconducting nanowires under electric field

This study applies the time-dependent Ginzburg–Landau (TDGL) theory with thermal noise to analyze the thermoelectric and transport properties of superconducting Sn nanowires, focusing on the thermopower (αxx) and the phase transition characteristics in the S-shaped J-E curves. We observe significant contributions from superconducting Cooper pairs, which remain nonzero above the critical temperature (Tc), indicating residual superconductivity due to strong thermal fluctuations. The S-like shape in the J-E curves is attributed to a dynamical instability transition temperature (T∗) at approximately 2.9 K, where thermal fluctuations dominate. Furthermore, we compare the resistance in the linear response to experimental data for Sn nanowires both below and above Tc. Below Tc, the resistance sharply decreases, reflecting the robust superconducting state, while above Tc, it increases, aligning with normal state behavior. In nonlinear response case, our results indicate that high electric fields can be effectively used to suppress order-parameter fluctuations and the electrical conductivity in superconducting nanowires. The findings provide critical insights into the thermoelectric behavior and phase transitions in Sn nanowires, highlighting the importance of Cooper pair dynamics in shaping the transport properties of one-dimensional superconductors. This understanding is essential for the development of advanced nanoelectronic devices leveraging these unique superconducting properties.

Influence of Disorder in High-Entropy Alloys on Thermoelectric Properties and Phase Stability

Influence of Disorder in High-Entropy Alloys on Thermoelectric Properties and Phase Stability

Performance analysis of a battery thermal management system combining thermoelectric, composite phase change material, and liquid cooling under extreme operating conditions

To maintain optimal operating temperatures for lithium-ion batteries under extreme operating conditions, a battery thermal management system (BTMS) integrating the thermoelectric cooler (TEC), liquid cooling, and composite phase change material (CPCM) is developed. Moreover, a transient numerical model has been established, considering thermal, electrical, and fluid multiphysics fields, to precise evaluation the system's performance. The outcomes indicate a decrease in both the maximum battery temperature and CPCM liquid fraction as the expanded graphite (EG) mass fraction, TEC cooling input current, and coolant flow speed increase. Furthermore, the temperature difference among batteries exhibits a decrease as the EG mass fraction increases, but experiences an elevation with an increase in both current and coolant flow speed. The BTMS features the lowest power consumption and optimal cooling performance at the EG mass fraction of 12 %, the TEC cooling input current of 3 A, and the coolant flow speed of 0.05 m/s. In preheating situations, the battery pack can achieve a temperature of 293.15 K starting from 263.15 K with the assistance of TEC preheating input currents of 4 A and 5 A, taking 5600 s and 2240 s, respectively, to complete the entire preheating procedure. This study will offer new insights into the advancement of the BTMS, allowing for the control of battery temperatures in high-temperature and high-discharge rate conditions, coupled with preheating at low-temperature.

Growth of Textured Chalcogenide Thin Films and Their Functionalization through Confinement

A number of chalcogenides show a remarkable portfolio of properties, which enables a plethora of applications including thermoelectric power generation and phase change material (PCM)‐based information storage. PCMs exhibit fast and reversible switching between two (typically, amorphous and crystalline) states, characterized by different optical and electrical properties. In the last decade, textured chalcogenide thin films have been investigated to develop a better understanding of structure – property relationships, improve material performance and understand how these properties change upon reducing film thickness. In this review, the present knowledge concerning the textured growth is summarized, focusing on films of GeTe, Sb2Te3, and GeSbTe compounds. In particular, the impact of different deposition methods, substrate surface modifications, and methods to influence film formation is reviewed. In the second part of this review, confinement effects are discussed. Surprisingly pronounced changes in atomic arrangement, that affect film properties, and device performance are presented. These changes are attributed to the unconventional bonding mechanism in these chalcogenides coined metavalent bonding, which is trongly affected by the confinement. Bonding becomes covalent‐like in the two‐dimensional limit, whereas Metavalent Bonding emerges for thicker films, where electron delocalization is increased This explains the pronounced property changes with film thickness.

Effect of laser wavelength on the thermoelectric properties of Bi1.6Pb0.4Sr2Co2O8 textured ceramics processed by LFZ

Bi1.6Pb0.4Sr2Co2O8 samples have been textured by the Laser Floating Zone (LFZ) process using Nd:YAG, and CO2 laser radiation. Using different wavelengths resulted in significant structural and microstructural modifications. Powder XRD patterns showed that the thermoelectric phase is the major one in both cases. Microstructural studies revealed that all samples presented the same phases but with much lower content of secondary ones in those processed with the CO2 laser. Electrical resistivity showed different behavior for the two types of samples, being in general, lower for the CO2 grown rods. Seebeck coefficient is lower for the CO2 grown samples up to 300 °C, and higher in the high-temperature range, reaching 240 μV/K at 650 °C, which is one of the highest values obtained so far in these compounds. Moreover, thermal conductivity at 600 °C for these samples (0.93 W/K m) is among the lowest reported in the literature. As a consequence, ZT values at 600 °C reached 0.42 in CO2 textured materials, about two times higher than the obtained in Nd:YAG ones. This value is among the highest reported so far in the literature, and is comparable to the performance attained for the same composition containing nanoparticles addition. All these properties, combined with the fact that the processed materials can be directly integrated into thermoelectric modules, render them highly attractive for industrial production.

Contribution of the carbon tax, phase-out of thermoelectric power plants, and renewable energy subsidies for the decarbonization of Chile − A CGE model and microsimulations approach

There are various climate policies to decarbonize the energy matrix of a country. In the case of Chile, a carbon tax of 5 USD/tCO2 was initially implemented, and later, a schedule was established for the phase-out of coal-fired thermoelectric plants, all the above in the absence of subsidies for non-conventional renewable energy (NCRE). This study uses a computable general equilibrium (CGE) model and microsimulations to assess the contribution of current climate policies and other more demanding scenarios that accelerate the decarbonization of the Chilean energy matrix, considering economic, environmental, and distributional impacts. Specifically, carbon taxes are simulated with and without complementary climate policies (phase-out of coal-fired power plants and NCRE subsidies). The results show that the scenarios that combine the three climate policies generate a greater decrease in greenhouse gas emissions (40.4% ∼ 57.5%). Besides, the drop in GDP is more pronounced when coal-fired thermoelectric plants phase out (0.3% additional), and NCRE subsidies contribute to moderately reducing emissions. However, NCRE subsidies reduce the negative effect on households’ expenditure and income, especially in the poorest quintile. Finally, microsimulations show marginal changes in income distribution and an increase of up to 0.4 percentage points in the poverty rate.

Performance investigation and design optimization of a battery thermal management system with thermoelectric coolers and phase change materials

In this work, a novel battery thermal management system (BTMS) integrated with thermoelectric coolers (TECs) and phase change materials (PCMs) is developed to ensure the temperature working environment of batteries, where a fin framework is adopted to enhance the heat transfer. By establishing a transient thermal-electric-fluid multi-physics field numerical model, the thermal performance of the BTMS is thoroughly examined in two cases. The findings demonstrate that increasing the TEC input current, fin length, and thickness is beneficial for reducing the maximum temperature and PCM liquid fraction. Nevertheless, although the increase in fin length can lower the temperature difference, the influence of fin thickness and TEC input current on the temperature difference is tiny. Based on the numerical findings, the optimal fin length and thickness of 7 mm and 3 mm are obtained. In this situation, when the TEC input current is 3 A, the maximum temperature, temperature difference, and PCM liquid fraction in Case 1 are 315.10 K, 2.39 K, and 0.002, respectively, and those are respectively 318.24 K, 3.60 K, and 0.181 in Case 2. The configuration of Case 1 outperforms that of Case 2, due to the fewer TECs and greater distance from the battery pack to the TEC within Case 2. When experiencing a higher battery discharge rate, the TEC input current should also be correspondingly increased to ensure the temperature performance of the battery. The relative findings contribute to new insights into battery thermal management.

Controlling thermal runaway by simultaneous use of thermoelectric module and phase change material in the lithium-ion batteries of electric vehicles

This work examines the experimental investigation of different kinds of thermal management systems (TMSs) for lithium-ion batteries (LIBs) in electric vehicles. The investigation primarily focused on the battery thermal management system (BTMS) utilizing phase change material (PCM). The addition of the thermoelectric cooling system subsequently improved the BTMS. The findings indicate that when employing just PCM, the mean temperature reaches 85 °C, beyond the acceptable temperature range for battery safety. The use of the thermoelectric module in conjunction with the PCM has resulted in an elevation of the mean temperature of the battery to 76 °C within the specified timeframe. This outcome serves as a testament to the efficacy of the thermoelectric cooling system in further diminishing the average temperature of the battery. However, it should be noted that the battery's temperature remains within a hazardous threshold, thereby increasing the likelihood of thermal runaway and compromising the battery's overall performance and safety. The implementation of aluminum circular fins on the battery has resulted in a reduction in the average temperature from 76 °C to 65 °C. The alteration of the fin configuration from circular to axial fins resulted in the attainment of an average temperature of 48 °C.

Achieving n-type Conduction in AMg2Sb2 (A = Yb, Eu, Ca, Sr, Ba) Zintl Phases

Zintl phases have been theoretically predicted to be promising n-type thermoelectric materials, which, however, are very difficult to achieve experimentally, owing to the existence of intrinsic negatively charged defects. Here, taking the representative AMg2Sb2 (A= Yb, Eu, Ca, Sr, Ba) as the examples, we theoretically found that the defect formation energy of negatively charged A and Mg vacancies near the conduction band minimum are lower than other types of defects, playing as the vital role in hindering the experimental realization of n-type conduction. Experimentally, by suppressing the formation of A and Mg vacancies, n-type conduction can be successfully achieved in all the studied AMg2Sb2 Zintl phases. Moreover, taking EuMg2Sb2 as an example, its n-type thermoelectric performance can be significantly improved through further isoelectronic alloying and donor doping. This work highlights the importance of understanding intrinsic defects as a guide for the development of n-type thermoelectric Zintl phases.

Numerical investigations of concentrated photovoltaic thermal system integrated with thermoelectric power generator and phase change material

Numerical investigations of concentrated photovoltaic thermal system integrated with thermoelectric power generator and phase change material

Impact of external electric resistance on the power generation in the thermoelectric energy harvesting blocks

Energy can be harvested from various energy sources within a building. In this study, a thermoelectric generator-assisted energy harvesting block was proposed, aiming to utilize the waste heat source of the exterior wall of the building. The energy harvesting block comprises a thermoelectric generator and phase change material for converting waste heat from the building envelope and heat flux from the outside into electricity. Multiple energy harvesting blocks are required to construct an energy harvesting block wall. Thus, the electrical arrangements of multiple energy harvesting blocks and their effects on external resistance were analyzed. The arrangements consisted of a series array, parallel array, and combination array. Experiments were performed with a total of nine cases by connecting 1.6 Ω, 15 Ω, and 60 Ω with the same external resistance as the internal resistance of each array. The temperature and closed-circuit voltage were measured based on the sol-air temperature profile in December. The voltage and current were more affected by the connected external resistance than by the type of array. The maximum generated energy was 0.837 Wh/day when 60 Ω was connected to the series arrangement. In terms of the generated energy, the series arrangement was the most advantageous.

Integration of thermal insulation and thermoelectric conversion embedded with phase change materials

The thermoelectric effect can convert waste heat into electricity. The present work presents an integrated system of Thermoelectric Generators (TEG) and Phase Change Materials (PCMs) for thermal insulation of high-speed vehicles, where high heat fluxes of large fluctuations make thermal protection and energy harvest challenging. A single-stage thermoelectric generator is prepared with phase-change materials embedded to absorb and convert excessive heat. The performance is evaluated experimentally and numerically, between which a reasonable agreement is observed. The maximum temperature at the outside surface is reduced by 200 K, and the temperature curves are flattered. Furthermore, two-stage and two-segment integrated systems are numerically evaluated, generating a data set of thermoelectric performance. An artificial neural network is developed for prediction and a genetic algorithm is employed for optimization. The maximum specific power can be improved to 570 W/m2 in the two-segment system, while the temperature variation at the hot side of TEG in the two-stage system can be reduced to 230 K. Finally, a discussion on the effects of PCMs parameters is performed. Overall, the present work not only demonstrates the feasibility of such an integrated system but also illustrates the whole procedure of the predictions and optimizations. This could inspire more development for advanced integrated systems for thermal management.

Performance enhancement of photovoltaic panels integrated with thermoelectric generators and phase change materials: Optimization and analysis of thermoelectric arrangement

Performance enhancement of photovoltaic panels integrated with thermoelectric generators and phase change materials: Optimization and analysis of thermoelectric arrangement

Unraveling the structural details and thermoelectric transports of 2D-3D hetero-structure composites

With in-depth research on the thermoelectric properties of the single-phase traditional three-dimensional (3D) and emerging two-dimensional (2D) materials, there is a deficit in the study of the 2D-3D hetero-structure phases, whose structural details and transport features still require a clear understanding. In this work, taking 2D-SnSe and 3D-PbSe as research objects, we prepared mixture-phase composites with the coexistence of 2D and 3D phases and studied the relationship between the thermoelectric transports and phase structures. By conducting the powder X-ray diffraction measurements and Rietveld refinements, we obtained the dynamic 2D-3D hetero-structure compositions of weight percentages with heating-cooling cycles. Subsequently, we estimated the lattice thermal conductivity from the experimental measurements and theoretical calculations as functions of 2D-3D compositions. We discovered that the lattice thermal conductivity reduction became more obvious in the samples with small amounts of hetero-structure phases, benefiting from the extra scattering of phonons by the higher density of hetero-structure interfaces. Moreover, we observed the 2D-3D hetero-structures at the microscopic scale by HADDF-STEM, experimentally confirming the presence of low symmetrical-PbSe and high symmetrical-SnSe phases. This study gave a perspective and investigation method to unravel both the structural details and transport properties of 2D-3D hetero-structure composites, which might provide new strategies for optimizing thermoelectric performance by depressing the thermal transports in hetero-structure materials.

Anomalous grain growth in sintered Bi2Ca2Co2−xCuxOy + Ag ceramic composites by Cu doping

Bi2Ca2Co2 − xCuxOy + 4 wt%Ag (with x between 0 and 0.20) thermoelectric materials were prepared through a sol-gel method via nitrates. Powder XRD patterns showed the presence of thermoelectric phase as the major one, accompanied by metallic silver. SEM observations identified three different secondary phases in the samples, together with an exaggerated grain growth with Cu doping. The microstructural modifications are reflected in an important decrease of electrical resistivity, ∼ 3% when compared to undoped samples, due to the reduction on the number of grain boundaries, and the increase of Co4+ in the conducting layer. The minimum values at 650 ºC were obtained in 0.10 Cu-doped samples, 69 mΩ cm, which are lower than the reported in sintered samples. On the other hand, Seebeck coefficient was only slightly affected and reached the highest values at 650 ºC in 0.15 Cu-doped samples, 215 µV/K, which is practically the same measured in undoped ones, 211 µV/K, and lower than those reported for sintered samples. Consequently, the highest PF at 650 ºC has been determined in 0.10 Cu-doped samples, which is around 50% higher than the obtained in samples prepared through the classical solid-state method, or the undoped ones prepared in this work.

Experimental study of a novel hybrid photovoltaic/thermal and thermoelectric generators system with dual phase change materials

Photovoltaic (PV) cell technology has evolved dramatically since its invention. However, the adverse effects of the rise in the temperature of solar cells on electrical efficiency are still a problem, and the methods to control it are of great interest. Deploying thermoelectric generators (TEG) and phase change materials (PCM) have been scrutinized in recent years. PCMs impede the system from heating up by absorbing thermal energy at the melting temperature. TEGs exploit the temperature gradient in systems and generate electricity. In this experimental investigation, a PV/T-TEG-2PCM with two different PCM materials and metallic heat transfer enhancers; and another setup of PV/T-TEG were assembled, simultaneously examined, and operational parameters were measured. Performance of both systems from thermal and electrical energy and exergy perspectives were compared. Results showed that the proposed PV/T-TEG-2PCM with two PCMs was superior to the PV/T-TEG configuration in every area. The proposed PV/T-TEG-2PCM was able to decrease the average solar cell temperature and increase the TEG temperature gradient up to 89.4% and 1.2%, respectively. The mean electrical energy and total exergy efficiencies of the PV/T-TEG-2PCM system were 8.1% and 9.9% higher than the PV/T-TEG system, respectively.

Numerical simulation of hybrid battery thermal management system combining of thermoelectric cooler and phase change material

In this study, a hybrid BTMS (battery thermal management system) that combines TEC (thermoelectric cooler) and PCM (phase change material) is shown. The PCM absorbs heat and occurs in phase change, which stores the heat from batteries. The TECs act as a heat pump, takes away the excess heat in the PCM through the fins, and control the temperature of the PCM below the phase transition temperature as much as possible, which can prevent it from melting completely and losing the ability to keep the battery temperature stable. By comparative analysis, the addition of PCM can obtain better temperature uniformity, the temperature difference was controlled below 6 °C, and CPCM with higher thermal conductivity was more suitable for the hybrid BTMS, at 1200 s, the maximum temperature of the model with 30% EG/RT44HC was 10.3 °C lower than that with pure RT44HC. When the fill thickness of CPCM increases, the temperature control time can be extended, but the performance of TEC will decrease. For this model, the arrangement direction of the fins should be perpendicular to the direction of the battery which has higher thermal conductivity, heat from batteries can be effectively transferred to the fins more and faster.

Insights into the Classification of Nanoinclusions of Composites for Thermoelectric Applications

Thermoelectric composites are known for their enhanced power conversion performance via interfacial engineering and intensified mechanical, structural, and thermal properties. However, the selection of these nanoinclusions, for example, their type, size effect, volume fraction, distribution uniformity, coherency with host, carrier dynamics, and physical stability, plays a crucial role in modifying the host material thermoelectric properties. In this Review, we classify the nanoinclusions into five types: carbon allotropes, secondary thermoelectric phases, metallic materials, insulating oxides, and others. On the basis of the classification, we discuss the mechanisms involved in improving the ZT of nanocomposites involving reduction of thermal conductivity (κ) by phonon scattering, improving the Seebeck coefficient (α) via energy filtering effect and the electrical conductivity (σ) by carrier injection or carrier channeling. Comprehensibly, we validate that adding nanoinclusions with high electrical and low thermal conductivity as compared to the matrix material is the best way to optimize the interlocked thermoelectric parameters. Thus, collective doping and nanoinclusions in thermoelectric materials is the best possible solution to achieve a higher power conversion efficiency equivalent to other renewable energy technologies.

Simultaneous Enhancement of Thermoelectric Power Factor and Phase Stability of Tin-Based Perovskites by Organic Cation Doping

Simultaneous Enhancement of Thermoelectric Power Factor and Phase Stability of Tin-Based Perovskites by Organic Cation Doping

Detailed low temperature studies on thermoelectric performance of K-doped Bi2Ca2Co2Oy ceramics fibers

The effect of K substitution for Ca in Bi2Ca2-xKxCo2Oy (x = 0.0, 0.05, 0.075, 0.10, and 0.125) thermoelectric ceramics, produced via laser floating zone (LFZ) method, have been systematically investigated. XRD patterns are quite similar for all samples and main peaks in the patterns correspond to reflection planes of the thermoelectric phase together with small amount of secondary phases. SEM micrographs revealed well oriented grains along the growth direction, and the presence of three different contrasts, associated through EDS to different phases, namely, black (Co oxide), white (Bi poor phase) and grey (Bi2Ca2Co1.7Oy TE phase). It was also seen that the amount of secondary phases diminishes with K-increase. The room-temperature resistivity values sharply decrease from 0.75 mΩ.m for the undoped sample to 0.44 mΩ.m for the 0.05 K-doped one, increasing for higher doping. Seebeck coefficient also decreases from 190 μV K−1 in the pristine sample, to 160 μV K−1 in all the K-doped ones, at 390 K. Thermal conductivity increases with temperature up to around 250 K, decreasing at higher temperatures. Thermal conductivity at 390 K decreases from 1.1 W K−1 m−1 in the pristine sample to lower values by K-doping, reaching the minimum, 0.9 W K−1 m−1, in the 0.125 K-doped one. As a result, the highest ZT value of has been determined in 0.05 K-doped sample, around 0.021 at 390 K.