We conducted a comprehensive study on the transition-metal compositional dependence of the anomalous Nernst effect (ANE) in amorphous (amo.) Tb-Fe-Co thin films. The anomalous Nernst coefficient strongly depends not only on the Tb composition but also on the transition metal composition, reaching a maximum of 1.8 mu V/K for amo. Tb-11.0(Fe50.0Co50.0)(89.0). By evaluating the electrical and thermoelectric properties, it was clarified that this maximum is achieved by the superposition of two large contributions: S-1 arising from direct transverse electron conduction due to a temperature gradient and S-2 resulting from the combined Seebeck and anomalous Hall effects. By examining the transition-metal composition dependence in detail, we discovered that, despite being amorphous structures, the 3d electrons of the transition metal could be sensitively contributing to the ANE and anomalous Hall effect as if they were electron-doped. Our research provides insights for enhancing the ANE in amorphous structures.

Wearable thermoelectric generators (TEGs) are fundamentally constrained by the inverse relationship between device thickness and achievable temperature gradient, a trade-off that has persistently limited their practical power output and hindered their deployment in self-powered wearable electronics and IoT devices. Here, we introduce a stair-shaped thermoelectric device architecture that effectively decouples this intrinsic constraint, enabling significantly enhanced thermal gradients without compromising device conformability. Guided by coupled electrothermal finite-element simulations and validated through systematic experimental studies, a Cu wire electrode integrated with an aerogel substrate is demonstrated as a highly effective configuration for maximizing the temperature gradient in a fully wearable form factor. The fabricated device delivers a maximum output power of 2.6 mu W at a temperature gradient of similar to 14 K, with a power density of 2.6 mu W.cm(-2), representing the highest reported output among fully conformable WTEGs operating under near-body-temperature conditions without external heat-guiding structures. Despite a higher internal resistance relative to many prior reports, the exceptional temperature gradient achieved by the stair-shaped architecture yields a superior open-circuit voltage within the class of fully conformable WTEGs without external heat-guide structures. Beyond the specific device demonstrated here, the stair-shaped architecture may be extended to other ductile thermoelectric materials providing a useful design concept for improving thermal-gradient management in next-generation flexible thermoelectric generators.

We investigated the thermoelectric effects of the Dirac electron system Ag2Te under magnetic field. Our anal-ysis based on the Boltzmann semiclassical model associated the disorder with the unconventional magnetic field responses such as linear magnetoresistance, linear Nernst effect, step-like Nernst effect, and sign change in Nernst effect. The analysis also revealed the impurity band near the Fermi energy. We simultaneously clari-fied the serious impact of the thermal Hall effect on the measurement of the Nernst effect, and we proposed the definitive solution. Our careful measurement and analysis will be the standard for the thermoelectric study under magnetic field.

Thermal management technologies have attracted considerable interest from demands on energy saving, carbon neutral, the temperature control of nano-scale devices, etc. In this study, we developed a thin-film heat-flow-switching-device working with small variation of device temperature by making full use of the unique temperature dependence of the thermal conductivity of Ag2+alpha SxSe1-x. Their thermal conductivity was carefully investigated using the time-domain thermoreflectance (TDTR) method, and a large variation of thermal conductivity exceeding kappa(_large)/kappa(_small) = 2.5 was observed. We found that this large variation in heat flux was caused by a thermal pumping phenomenon attributed to the latent heat at the phase transition of Ag2+alpha SxSe1-x. To gain a deeper insight into the thermal pumping phenomenon, we investigated the composition and thickness dependence of heat flux change for the devices consisting mainly of Ag2+alpha SxSe1-x. Larger changes both in entropy and phase transition volumes resulted in a significant increase in heat absorption. An improved devices was developed with the optimized composition and the optimized film thickness, and the heat flux of the optimized device showed an extraordinary value of J(Q_large)/J(Q_small) approximately equal to 30-40 induced by 5 K change in device temperature.

An electric double-layer capacitor-based heat flow switching device working with a bias voltage was developed as a key technology of thermal management. This device allows us to rapidly control the magnitude of heat flow passing through the device using variations in electronic thermal conductivity of component material induced by the bias voltage. We employed a thin film of Ag2S0.8Se0.2 as the most important component material, because it possesses an exceptionally low lattice thermal conductivity and a semiconducting electronic structure. The thermal conductivity of the fabricated device was measured by means of a periodic heating method under various applied bias voltages. The thermal conductivity of Ag2S0.8Se0.2 was found to increase linearly with increasing bias voltage VB up to a factor of 1.9 at VB = 2.4 V. The transient current response during the charging and discharging processes revealed that the response time for switching was fast enough to be less than 0.2 sec. By measuring the stored charge and comparing it with the electronic thermal conductivity, we confirmed that the observed variation in thermal conductivity of the component material is attributed to the accumulated charge in the material.

Abstract Zinc telluride (ZnTe) is a promising wide-bandgap thermoelectric host, but its low intrinsic hole concentration and stiff, highly conductive lattice have historically restricted its figure of merit ( zT ). Here, we report a systematic comparative study of Cu and Ag doping in bulk p -type Zn 1− x M x Te 1+ x (M=Cu, Ag; x = 0, 0.01, 0.05, 0.10) synthesized via melt-quenching and spark plasma sintering, demonstrating that a single design variable—dopant ionic radius—governs both electronic and thermal transport channels. Both elements substitute as monovalent acceptors on Zn 2+ sites, raising the Hall carrier concentration to 4.75 × 10 19 cm −3 at 300 K and ∼3.6 × 10 20 cm −3 at 773 K. First-principles calculations reveal that substitution lowers local tetrahedral site symmetry and splits the threefold-degenerate Te-5 p valence-band edge by 60.5 meV (Cu) and 73.7 meV (Ag)—scaling with ionic radius rather than d -band position, establishing a steric rather than p – d orbital origin. Because both splittings are comparable to k B T ≈58 meV at 673 K, all three valence sub-bands remain thermally co-populated. The measured Seebeck coefficient corroborates this band convergence, yielding a density-of-states effective mass of m DOS * ≈1.3–1.4 m e more than double the single-band value. Concurrently, ionic size mismatch generates 0.45% microstrain, localized nanoscale strain fields, and coherent Ag 2 Te precipitates. This three-tiered phonon scattering hierarchy depresses the lattice thermal conductivity to 0.36 W m −1 K −1 at 873 K—touching the theoretical Cahill minimum limit—while coherent phase boundaries preserve hole mobility. Although Cu doping achieves a marginally higher electronic power factor, Ag doping prevails decisively in thermal transport suppression, yielding a peak figure of merit zT ≈0.75 at 673 K compared to 0.64 at 773 K for Cu. Dopant ionic size thus emerges as a vital design parameter for defect engineering in lead-free wide-bandgap chalcogenides.

Manganese spinel ferrite (MnFe2O4) thin films were deposited by Pulsed Laser Deposition (PLD) at different temperatures to study the effect of growth conditions on their structural, thermoelectric and magnetic properties of the samples. X-ray diffraction reveals a progressive increase of crystallinity and a preferential orientation along the [311] direction of the spinel structure with increasing deposition temperature. The thin films, with an average thickness of similar to 180 nm, show in-plane isotropic reduced remanent magnetization, (M-r/M-max), whereas both the M-r/M-max and coercivity (H-C) are systematically lower in the out-of-plane direction. These magnetic parameters strongly depend on the deposition temperature, reaching maximum values of M-r/M-max similar to 0.7 and H-C similar to 0.4 kOe for films grown at 773 K. Thermoelectric measurements show a negative Seebeck coefficient (S) over the investigated temperature range (313-613 K), consistent with n-type conduction. The Seebeck coefficient remains relatively stable with temperature, varying from -3 & micro;V/K to -180 & micro;V/K across the series, while the electrical conductivity (sigma) increases from 0.1 S/m to about 1 S/m with increasing temperature. Both quantities are strongly affected by the deposition temperature, resulting in a maximum calculated power factor (PF) of 0.07 & micro;W/(m & centerdot;K-2) at 613 K for the film deposited at 473 K. These results are promising for the development of multifunctional materials with both magnetic and thermoelectric properties that can be tailored through different deposition temperatures.

Full Heusler alloys XInPd2 (X= Zr, Hf and Ti) have recently attracted significant attention owing to their symmetry-driven electronic structure and also due to the interplay between disorder and emergent ground states. Within this family, Pd2ZrIn serves as a unique platform to study the effect of disorder on superconducting pairing. This alloy crystallizes in a cubic L21 structure with significant B2-type antisite disorder. Electrical resistivity and magnetic susceptibility studies confirm bulk type-II superconductivity with a transition temperature TC 2.2 K. Zero-field μSR results reveal no evidence of spontaneous internal magnetic fields below TC, confirming the preservation of time-reversal symmetry. Transverse-field μSR spectra show the formation of a vortex lattice, consistent with type-II superconductivity, and the superfluid density is well described by a fully gapped, nodeless s-wave state with superconducting gap Δ (0) 0.33 ±0.01 meV. Furthermore, the estimated ratio of transition temperature and Fermi temperature (TC/TF) indicates that this alloy lies within the conventional superconducting regime on the Uemura plot. These results establish Pd2ZrIn as a weakly coupled, dirty-limit, type-II superconductor; with a fully gapped, nodeless order parameter and preserved time-reversal symmetry.

In view of the electrical transport optimization in thermoelectric films, a p- and a n-conducting doubly-filled skutterudite belonging to the system (La,Sm)y(FexNi1–x)4Sb12, were deposited as thin films by pulsed laser deposition, and subsequently annealed under different conditions to assess how the post-deposition treatment affects structural and electrical properties. X-ray diffraction data reveal the occurrence of a preferential orientation along the planes belonging to the {310} family, which tends to disappear with increasing the annealing temperature. Within the considered span, the lowest (423 K) and the highest (523 K) annealing temperatures are the most suitable for achieving optimal power factors in the p- and n-type film, respectively. This evidence is discussed in terms of competition between degradation of the film and progressive structural reorganization toward long-range order. The study underscores the need for a careful choice of the post-deposition thermal treatments aimed at the optimization of the electrical properties and power factor of filled skutterudite thin films.

We have studied the origin of zero volume expansion below the Curie temperature (Tc), variable range hopping (VRH) behavior using structural, magnetic, transport and thermal studies on the oxygen deficient double perovskite NdBaCo2O5+δ(δ∼0.65). The valence state of Co ions and the possible properties exhibited by such compound were studied using electronic structure calculations forδ= 0.75. Careful investigation of structure shows that the compound stabilizes in tetragonal structure (P4/mmm) having2ap×2ap×2ap(222) superstructure, where apis the cubic perovskite lattice parameter. The compound exhibits a minimum in resistivity, ferromagnetic (FM) and ferrimagnetic (FeM) transitions around 375 K, 120 K (Tc) and 60 K, respectively with signature of Griffiths phase aboveTc. Our detailed structural analysis suggests signature of the onset of the above magnetic transitions at temperatures well above its stabilization at long range level thereby leading to VRH behavior. The observed zero thermal expansion in volume belowTcappears to be due to competing magnetic interactions within and between the magnetic sublattices. Our electronic structure calculations in FM and FeM configurations show (a) Co ions stabilize in intermediate spin (IS) state, having oxidation state less than +3, (b) half metallicity, (c) the behavior of the density of states is in line with the resistivity results, and (d) unusually high orbital angular moment in Co ions with inclusion of spin orbit coupling (soc). Our results show the possibility of coupling between magnetism and ferroelectricity. We believe that our results especially on the valence state of the Co ion, zero thermal expansion in volume, short range magnetic orderings and the connection between different degrees of freedom will be helpful in clearing the ambiguities existing in literature on the nature of magnetism and thereby aiding in designing new functionalities by maneuvering the strength of soc.

This review summarizes our recent developments in capacitor-type heat flow switching devices that enable active control of heat flow magnitude through the modulation of electron thermal conductivity. We initially demonstrated the feasibility of a capacitor-type heat flow switching device using silver chalcogenides, Ag2S1-x Se x , as an electrode material with very low lattice thermal conductivity (≤0.5 W m-1 K-1). We achieved significant enhancements in heat flow switching performance through subsequent improvements, including electrode thinning and the implementation of an electric double-layer capacitor structure with ionic liquids. The switching ratio improved from an initial value of 1.1 at the bias voltage of V B = +3 V to 1.9 at V B = +2.4 V, while response times were estimated to be less than 0.2 s. This review discusses the operating principles, experimental methods, and performance metrics across different device configurations, highlighting the critical role of electrode materials with extremely low lattice thermal conductivity. Our findings establish a promising candidate for practical thermal management applications that require rapid and reliable heat flow control without mechanical components.

In this study, we developed a method for reproducibly fabricating high-performance nano-grained bulk Si-Ge thermoelectric materials free from severe oxidization. In our previous work, the oxidization of Si-Ge during mechanical alloying and sintering processes had led to poor reproducibility of the value of electrical resistivity. We found that co-sintering with Ti, which is more easily oxidized than Si and Ge near the sintering temperature, effectively reduces the oxygen concentration in the nano-grained bulk Si-Ge samples. The oxygen concentration in the sample co-sintered with Ti was found to be less than 2.4 at.%, and electrical resistivity was found to be less than 3.9 m Omega cm at 922 K with good reproducibility. High Seebeck coefficient (more than 400 mu V K-1) and low thermal conductivity (less than 1 Wm-1K-1) were simultaneously achieved by constructive electronic structure modification via iron doping and nano-crystallization, respectively. As a consequence, we succeeded in obtaining a surprisingly large value of dimensionless figure of merit, ZT = 4 at 922 K, and the temperature range of ZT exceeding 1 extended at high temperatures above 700 K.

In the field of thermoelectric materials and devices, improving energy conversion efficiency remains a long-standing challenge. As a promising approach to address this issue, utilizing energy-dependent electron-scattering beyond the ordinary constant relaxation time approximation (CRTA) has been proposed. However, direct experimental evidence for an energy-dependent scattering reflected in the Seebeck coefficient is still lacking. Here we demonstrate using angle-resolved photoemission spectroscopy that the relaxation time of heavy fermion quasiparticles is highly dependent on the energy near the Fermi level. The observed energy dependence of the relaxation time is due to the coherent Kondo scattering, describing the sign of the Seebeck coefficient reasonably well, which cannot be deduced from CRTA. Our findings provide not only deeper insight into the understanding of thermoelectricity in correlated materials, but also future perspectives on possible orbital-selective engineering of thermoelectric materials.

For developing high-performance composite-type thermal diodes, this study focuses on silver chalcogenides, which undergo structural phase transitions in the temperature range of 350 K to 473 K, accompanied by a significant stepwise change in thermal conductivity. Ag2 + x Te0.9S0.1 (x = 0, 0.01, 0.02, 0.025, 0.03, 0.035, 0.04, and 0.05) and Ag2S1 - y Se y (y = 0.35, 0.375, 0.4, 0.425, and 0.45) samples were synthesized with precisely controlled compositions, and their temperature-dependent thermal conductivity across the phase transition was studied with the composition dependence. Ag2Te0.9S0.1 exhibits a stepwise decrease in thermal conductivity with transitioning from the low-temperature phase (LTP) to the high-temperature phase (HTP), and this behavior was further enhanced by adding excess Ag. The added silver precipitated in the LTP and dissolved into the HTP of Ag2Te0.9S0.1, resulting in a maximum thermal conductivity change (κ LTP / κ HTP) of 2.7-fold with the phase transition at x = 0.025. On the other hand, the Ag2S1 - y Se y samples exhibited a stepwise increase in thermal conductivity with transitioning from the LTP to the HTP, and the maximum thermal conductivity change of κ HTP / κ LTP = 5 was observed at y = 0.4. A composite thermal diode was fabricated using Ag2.025Te0.9S0.1 and Ag2S0.6Se0.4 with the length ratio of Ag2.025Te0.9S0.1: Ag2S0.6Se0.4 = 47:53 and, consequently, exhibited TRR = 3.3 when it was placed between heat reservoirs maintained at T H = 412 K and T L = 300 K. This TRR value is the largest ever reported for all-solid-state composite thermal diodes.

High-resolution angle-resolved photoemission spectroscopy (ARPES) performed on the single-layered cuprate (Pb1-y,Biy)2Sr2-xLaxCuO6+delta (Bi2201) reveals a 6-10% difference in the nodal kF vectors along the TY and TX directions. This asymmetry is notably larger than the 2% orthorhombic distortion in the CuO2 plane lattice constants determined using X-ray crystallography from the same samples. First principles calculations indicate that crystal-field splitting of the bands lies at the root of the kF asymmetry. Concomitantly, the nodal Fermi velocities for the TY quadrant exceed those for TX by 4%. Momentum distribution curve widths for the two nodal dispersions are also anisotropic, showing identical energy dependencies, bar a scaling factor of similar to 1.17 +/- 0.05 between TY and TX. Consequently, the imaginary part of the self-energy is found to be 10-20% greater along TY than TX. These results emphasize the need to account for Fermi surface asymmetry in the analysis of ARPES data on Bi-based cuprate high temperature superconductors such as Bi2201. To illustrate this point, an orthorhombic tight-binding model (with twofold in-plane symmetry) was used to fit ARPES Fermi surface maps spanning all four quadrants of the Brillouin zone, and the ARPES-derived hole-doping (Luttinger count) was extracted. Comparison of the Luttinger count with one assuming four-fold in-plane symmetry strongly suggests the marked spread in previously-reported Fermi surface areas from ARPES on Bi2201 results from the differences in kF along TY and TX. Using this analysis, a new, linear relationship emerges between the hole-doping derived from ARPES (pARPES) and that derived using the Presland (pPresland) relation such that pARPES = pPresland + 0.11. The implications for this difference between the ARPES-and Presland-derived estimates for p are discussed and possible future directions to elucidate the origin of this discrepancy are presented.

We conducted a comprehensive study on the compositional dependence of the anomalous Nernst effect (ANE) in amorphous (amo.) Tb-Fe-Co thin films. The anomalous Nernst coefficient strongly depends not only on the Tb composition but also on the transition metal composition, reaching a maximum of 1.8 uV/K for amo. Tb11.0(Fe50.0Co50.0) 89.0. By evaluating the electrical and thermoelectric properties, it was clarified that this maximum is achieved by the superposition of two large contributions: S_1 arising from direct transverse electron conduction due to a temperature gradient, and S_2 resulting from the combined Seebeck and anomalous Hall effects. We discovered that the anomalous Nernst conductivity, which is attributed to Berry curvature, varied significantly with the transition metal, even in an amorphous material lacking long-range crystalline order. Our research indicates that it is possible to control the electronic states that influence thermoelectric properties, even in the amorphous state.

The atomic structure and configuration of Si0.65Ge0.35Bx (x = 0, 0.01, 0.05, 0.10) powders prepared by long-time mechanical alloying are analyzed by X-ray total scattering measurement and transmission electron microscopy. The results show that the powders contain a large amount of the amorphous phase and a small amount of the crystalline phase. The structural parameters, including the fractions of the amorphous and crystalline phases, are obtained by pair distribution function (PDF) analysis applied to crystalline materials. There is a crystal growth mechanism attributable to small amounts of boron added, as a significant increase in crystalline phase fraction is only observed at x = 0.01. The angle of Bragg peaks does not shift monotonically with increasing amount of boron added. Furthermore, the lattice parameter shortening predicted from the peak shift exceeds that derived from boron substitution. This suggests the existence of another mechanism for lattice parameter change with boron doping. Crystal PDF analysis with a four-phase model consisting of three crystalline phases and one amorphous phase shows a decrease in the lattice constant of a B-doped Si–Ge crystal with increasing x, suggesting B substitution. Although not clear from this study, it is possible that boron doping or long-time mechanical alloying may have led to the formation of pure Si or a high-Si-concentration Si–Ge crystalline phase.

We investigate composition, time, temperature, and annealing-process dependences of crystalline and amorphous phases in ductile semiconductors Ag2S1−xTex with x = 0.3–0.6. We reveal that a metastable amorphous phase containing no secondary phases is obtainable at x = 0.6 even with furnace cooling and possesses ductility in the same manner as the end compound of Ag2S, while the high-temperature phase (HTP) of Ag2S precipitates in the amorphous phase at x = 0.3–0.5 by keeping the good ductility. During the crystallization process of the amorphous phase by annealing a sample at 373–503 K for 4–14 days and cooling it down slowly to room temperature, HTP of Ag2S disappears and the low-temperature phase (LTP) of Ag2S and the Ag5−dTe3 phase appear, while the amorphous phase remains. The ductility is observed for the samples containing the LTP of Ag2S but not for those containing the Ag5−dTe3 phase. Based on the obtained results, the possible phase diagram of Ag2S1−xTex with x = 0.3–0.6 is proposed, and the origin of the ductility in the LTP and HTP of Ag2S and amorphous phase is discussed. We believe that our study is helpful for properly predicting mechanical and transport properties of this material and developing this material as a component of bendable/wearable electronic devices for long-term use.

A detailed structural, magnetic as well as dielectric dynamics study is carried out to investigate the influence of Bi3+ on YCrO3. All the samples crystalize in orthorhombic structure with Pnma symmetry and the grains are mostly stretched with Bi. A coexisting tunable fraction of both antiferromagnetic (AFM) and weak ferromagnetic (WFM) phases is acquired by the system down to Low-T. An abnormal negative magnetization in zero field is correlated to the competition among AFM and WFM phases. Maximum magnetization decreases while the coercivity first increases and then decreases with Bi is correlated to the competing effect between the local deformation and Cr-O-Cr exchange interaction. The magnetodielectric coupling with improved permittivity might be associated with the 6s2 lone pair electron of Bi3+. Furthermore, ac-conductivity increases with a decrease in activation energy (0.27-0.11 eV), is explained in the framework of structural model and charge carrier hopping between Cr3+ and Cr4+ ions.

We report on the magnetic, electrical transport, caloric and electronic structure properties of TbFe4.4Al7.6polycrystalline alloy using experiment and theory. The alloy crystallizes in tetragonal structure with I4/mmm space group with lattice parametersa = b= 8.7234(5) Å andc= 5.0387(6) Å. It is ferrimagnetic with a compensation temperature ofTcmp∼151 K, Curie-Weiss temperatureθCW∼172.11 K and an effective magnetic momentμeff= (2.37±0.07)μB/f.u withZ= 2. At low temperatures, kinetic arrest-like first-order phase transition is realized through the thermal hysteresis between field-cooled cooling and field-cooled warming curves ofM(T) and virgin curves ofM(H) andρ(H)which are outside the hysteresis loops with metamagnetic transition. The high magnetic field suppression of multiple transitions and reduced coercive fieldHcoerand remnant magnetizationMremwith increasing temperature are reported.HcoerandMremcease to exist above the compensation temperatureTcmp. A correlation between the isothermal magnetization and resistivity is discussed. Specific heatC(T) analysis reveals a Sommerfeld parameter ofγ= 0.098 J⋅mol-1⋅K-2and a Debye temperature ofθD∼351.2 K. The sample is metallic as inferred from theρ(T)behavior and Sommerfeld parameter. The magnetoresistance of the alloy is low and negative which indicates the suppression of weak spin-fluctuations. This alloy avoids the tricritical point despite first-to-second order phase transition. The electronic and magnetic structure calculations, by making use of full potential linearized augmented plane wave method, suggest metallic ferrimagnetic ground state of TbFe4.4Al7.6with Tb atoms contributing ferromagnetically (5.87μB) and Fe atoms with antiferromagnetic contribution (2.67μB), in close agreement with the experimental observation.