Good Thermoelectric Performance Research Articles

Research progress on improving ionic conductivity of NZSP solid electrolyte

Due to the limited resources of lithium batteries, and the safety of liquid electrolytes, and the working principle of sodium batteries and lithium batteries are similar, and the cost is relatively low, so the development of sodium ion solid state batteries has its feasibility and necessity. Among them, NASICON solid electrolyte with its unique three-dimensional structure, and good thermoelectric performance has been widely concerned, in order to better understand the development of such materials and the latest developments, this paper reviews the crystal structure of NZSP solid electrolyte, conductive mechanism, preparation methods of research progress. NZSP solid electrolyte with its room temperature asymmetric monoclinic phase and large grain boundary resistance, resulting in ionic conductivity is not enough to meet the application needs, on the basis of the above content, for the existence of NZSP ionic conductivity low problem, related discussions were carried out. The research progress of improving the ionic conductivity of NZSP based on preparation technology, grain control and grain boundary control is discussed. And in the end, the possible future development trend of NZSP material is summarized and prospected, which will play a certain reference and promotion role for the future research on NASICON solid electrolyte.

Surface Modification of Bi2Te3 Nanoplates Deposited with Tin, Palladium, and Tin/Palladium Using Electroless Deposition

Surface-modified nanoplate-shaped thermoelectric materials can achieve good thermoelectric performance. Herein, single-crystalline Bi2Te3 nanoplates with regular hexagonal shapes were prepared via solvothermal techniques. Surface modification was performed to deposit different metals onto the nanoplates using electroless deposition. Nanoparticle-shaped tin (Sn) and layer-shaped palladium (Pd) formed on the Bi2Te3 nanoplates via electroless deposition. For the sequential deposition of Sn and Pd, the surface morphology was mostly the same as that of the Sn-Bi2Te3 nanoplates. To assess the thermoelectric properties of the nanoplates as closely as possible, they were compressed into thin bulk shapes at 300 K. The Sn-Bi2Te3 and Sn/Pd-Bi2Te3 nanoplates exhibited the lowest lattice thermal conductivity of 1.1 W/(m·K), indicating that nanoparticle-shaped Sn facilitated the scattering of phonons. By contrast, the Pd-Bi2Te3 nanoplates exhibited the highest electrical conductivity. Thus, the highest power factor (15 μW/(m∙K2)) and dimensionless ZT (32 × 10−3) were obtained for the Pd-Bi2Te3 nanoplates. These thermoelectric properties were not as high as those of the sintered Bi2Te3 samples; however, this study revealed the effect of different metal depositions on Bi2Te3 nanoplates for improving thermoelectric performance. These findings offer venues for improving thermoelectric performance by sintering nanoplates deposited with appropriate metals.

A van der Waals p-n heterostructure of GaSe/SnS2: a high thermoelectric figure of merit and strong anisotropy.

In recent years, van der Waals heterostructures (vdWHs) with controllable and peculiar properties have attracted extensive attention in the fields of electronics, optoelectronics, spintronics and electrochemistry. However, vdWHs with good thermoelectric performance are few due to the complex coupling of thermoelectric coefficients. Here, we employ density functional theory and Boltzmann's transport equation to explore the thermoelectric properties of the p-n vdWH of GaSe/SnS2, which has been experimentally observed to exhibit high performance as an optoelectronic device. We reveal that GaSe/SnS2 possesses strong anisotropy in terms of electronic transport resulting from the anisotropic carrier relaxation time. The longer carrier relaxation time in the y-direction for n-type induces a high power factor of 0.084 W m-1 K-2 at 300 K, while it is only 0.0087 W m-1 K-2) in the x-direction. The strong coupling of low-mid frequency phonon branches and the relatively weak Sn-S bond-induced anharmonicity hinder the phonon transport, which results in the lattice thermal conductivity of GaSe/SnS2 (14.61 and 15.43 W m-1 K-1 along the x- and y-directions at 300 K) being much smaller than the average value of GaSe and SnS2 (43.44 W m-1 K-1 at 300 K). The optimal thermoelectric figure of merit at 700 K for GaSe/SnS2 reaches 2.99, which is significantly higher than those of the constituents of GaSe (0.58) and SnS2 (1.04). The present work highlights the potential thermoelectric applications and the understanding of the thermoelectric transport mechanism for the recently synthesized p-n vdWH of GaSe/SnS2 with a high thermoelectric figure of merit and strong anisotropy.

Partially adsorption of hydrogen and fluorine-dependent thermoelectric performance enhancement in single-layer armchair graphene nanoribbons

In this paper, we newly investigated the thermoelectric properties of the armchair graphene nanoribbons formed by partially adsorption of hydrogen and fluorine atoms. The electronic band structure of the system with the good thermoelectric performance is characterized by concentrating several bands within the range of 0.2 eV of the conductive band minimum. Especially, the hybrid systems formed by 3 width adsorption with H and F atoms into middle part of GNR have the best thermoelectric characteristics. Moreover, the both edges termination by H atoms play a significant role in enhancement the electronic and thermoelectric properties. These results might be helpful for guessing the thermoelectric properties of the materials from their electronic band structures.

Investigation on prospective thermoelectrics — cubic Nd-doped LMO and rhombohedral Cu4Mn2Te4 materials — first principles approach

Structural, electronic, magnetic and optical properties of Cu4Mn2Te4 have been reported earlier by the authors, and here, the transport properties of the same are discussed along with the band structure investigation of the neodymium-doped cubic material LMO (LiMn2O4), namely LiMn[Formula: see text]Nd[Formula: see text]O4 compound, under spin polarized schemes through the First Principles calculations. The Full Potential-Linearized Augumented Plane Wave Method (FP-LAPW) method is adopted to investigate the electronic structures based on the framework of Density Functional Theory (DFT). Exchange potentials are treated using the Generalized Gradient Approximations (GGA). Cohesive energy calculations reveal that the ferromagnetic phase of LiMn[Formula: see text]Nd[Formula: see text]O4 and the antiferromagnetic phase of Cu4Mn2Te4 exhibits a stable phase. Of these, FM-LiMn[Formula: see text]Nd[Formula: see text]O4 shows a semi-metallic-like behavior in spin-up channel and metallic behavior in spin-down channel whereas antiferromagnetic Cu4Mn2Te4 exhibits a band gap in both spin-up and spin-down channels. Dirac points are identified at −0.0625[Formula: see text]eV in the band structure plot of FM-LiMn[Formula: see text]Nd[Formula: see text]O4 at its high symmetry points [Formula: see text] and W which is an indication of high electron mobility at ambient condition. The presence of flat and dispersive bands around the Fermi energy level is an indication of high thermopower, and it is present in both the compounds FM-LiMn[Formula: see text]Nd[Formula: see text]O4 and AFM-Cu4Mn2Te4. From the present computations, at 300[Formula: see text]K, a power factor range of ([Formula: see text] scaled by relaxation time in [Formula: see text]W/msK2) [Formula: see text] and [Formula: see text] is obtained for ferromagnetic LiMn[Formula: see text]Nd[Formula: see text]O4 compounds at up and down spins, respectively. A typical power factor ([Formula: see text]Wm[Formula: see text]s[Formula: see text]K[Formula: see text]) of [Formula: see text] and [Formula: see text] is obtained for antiferromagnetic Cu4Mn2Te4 at 325[Formula: see text]K required for good thermoelectric performance.

Ultra-flexible self-supporting Ag2Se/nylon composite films for wearable thermoelectric devices

Recently, flexible thermoelectric (TE) generators (f-TEGs) have received a lot of attention. Compared with TE films on flexible substrates, self-supporting composite films prepared by combining TE materials with soft fabrics and thus retaining the inherent advantages of fabrics, such as stretchability, breathability, and flexibility, are more practical and may significantly expand the application of f-TEGs in smart wearable devices. Hence, in this work, a facile and rapid method for preparing ultra-flexible self-supporting Ag2Se/nylon composite films is developed. The composite films with both TE properties and flexibility were obtained by fast selenization of commercial Ag/nylon fiber fabrics in a short time (60 s) at room temperature and then hot pressing at 230 °C in a vacuum. The maximum power factor of an optimized composite film at room temperature can reach 73.7 μW m−1 K−2. Meanwhile, the film exhibits excellent flexibility with the Seebeck coefficient and electrical conductivity decreased by only 7.37 and 8.48% after being bent 4000 repetitions around a round bar with a radius of 4 mm, which exceeds most reported flexible TE films. The ultra-high flexibility is mainly attributed to its high content of the nylon matrix (∼85.05 wt%), the tight bonding between Ag2Se grains, and the good combination between the Ag2Se and nylon matrix. In addition, a 3-leg f-TEG assembled with the optimal film produces a maximum power of ∼1.524 μW (corresponding to a power density of ∼0.47 W m−2) at a temperature gradient of 40.6 K, verifying the good TE performance of the composite film. This f-TEG can also be used as a self-powered temperature sensor, showing potential applications in daily life.

Prediction of structural, elastic, electronic and thermoelectric properties of the Rb3CuO and Rb3AgO anti-perovskites

The Structural, elastic and electronic and thermoelectric properties of anti-perovskites Rb3AgO and Rb3CuO compounds have been investigated using the full potential linearised augmented plane waves (FP-LAPW) method based on the density functional theory (DFT) implemented in the wien2k code. The analysis of the structural and elastic properties of Rb3AgO and Rb3CuO antiperovskites compounds were performed with mean of the generalized gradient potential approximation developed by Perdew–Burke–Ernzerhof (GGA-PBE) while the electronic and thermoelectric properties have been calculated using the GGA-PBE + TBmBJ approximation. In all calculations the spin-orbit coupling correction is tested which revealed it insignificant effect on the electronic properties and the related properties. These materials are found to be indirect narrow band gap semiconductors and exhibit good thermoelectric performance with a figure of merit ZTe ∼1. On the other hand, investigation of the phonon dispersion and the formation energy indicate the possible synthesize of these materials. In the absence of other theoretical and experimental results for Rb3AgO and Rb3CuO, this work is considered as a first prediction.

Study of the defect chemistry in Ag2Q (Q = S, Se, Te) by first-principles calculations

Ag2Q-based (Q = S, Se, Te) silver chalcogenides show great potential in thermoelectrics due to their suitable band gaps, high electron mobilities, and even remarkable ductility. Particularly, Ag2S and Ag2S/Se/Te solid solutions have been reported with both good ductility and thermoelectric performance, which are extremely suitable for the application in flexible wearables. However, the underlying mechanism of the native n-type conduction and p-type undopability for Ag2Q remains elusive. Herein, we use first-principles calculations based on density functional theory combined with GW correction to investigate the defect chemistry in Ag2Q. It is found that the site potential and Voronoi volume deviations resulting from Ag interstitials are noticeably smaller than those caused by Ag vacancies, which makes Ag interstitials with low formation energy more desirable during preparation, contributing to the native n-type conduction. The small and even negative dopability windows, on the other hand, account for the p-type undopability of Ag2Q. The calculated carrier concentrations of pristine Ag2Q are well consistent with the experimental observations, validating the reliability of our defect calculations. This work provides valuable guidance for first-principles calculation of defect chemistry in other narrow-gap semiconductors.

Good thermoelectric performance and stability in copper sulfide synthesized by hydrothermal method and densified by HP technique

Good thermoelectric performance and stability in copper sulfide synthesized by hydrothermal method and densified by HP technique

Self‐Healable and Stretchable PAAc/XG/Bi2Se0.3Te2.7 Hybrid Hydrogel Thermoelectric Materials

Thermoelectric power generators have attracted increasing interest in recent years owing to their great potential in wearable electronics power supply. It is noted that thermoelectric power generators are easy to damage in the dynamic service process, resulting in the formation of microcracks and performance degradation. Herein, we prepare a new hybrid hydrogel thermoelectric material PAAc/XG/Bi2Se0.3Te2.7 by an in situ polymerization method, which shows a high stretchable and self‐healable performance, as well as a good thermoelectric performance. For the sample with Bi2Se0.3Te2.7 content of 1.5 wt% (i.e., PAAc/XG/Bi2Se0.3Te2.7 (1.5 wt%)), which has a room temperature Seebeck coefficient of −0.45 mV K−1, and exhibits an open‐circuit voltage of −17.91 mV and output power of 38.1 nW at a temperature difference of 40 K. After being completely cut off, the hybrid thermoelectric hydrogel automatically recovers its electrical characteristics within a response time of 2.0 s, and the healed hydrogel remains more than 99% of its initial power output. Such stretchable and self‐healable hybrid hydrogel thermoelectric materials show promising potential for application in dynamic service conditions, such as wearable electronics.

Reversible Room Temperature Brittle‐Plastic Transition in Ag2Te0.6S0.4 Inorganic Thermoelectric Semiconductor

AbstractInorganic semiconductors with superior plasticity are highly desired in current flexible electronics, which however are rarely discovered owing to their intrinsic covalent and ionic bonds. The Ag2Te0.6S0.4 semiconductor with an amorphous phase has recently been reported to exhibit plastic deformability. In this study, the reversible brittle‐plastic transition is found in this inorganic semiconductor, and the plasticity of the Ag2Te0.6S0.4 sample is highly related to the phase structures. The Ag2Te0.6S0.4 with a monoclinic phase exhibits a brittle behavior, while the one with cubic‐crystalline/amorphous structure shows exceptional plasticity with a compressive strain of over 80%. Significantly, the reversible plastic‐brittle transition in Ag2Te0.6S0.4 inorganic semiconductor can be achieved by simple heat treatment. Besides the plasticity, the cubic‐crystalline/amorphous Ag2Te0.6S0.4 composites also possess good thermoelectric performance. This study uncovers the influence of phase structure on the mechanical properties of Ag2Te0.6S0.4 and realizes the reversible brittle‐plastic transition, facilitating its prospective application in flexible/wearable electronics.

Bilayer MSe2 (M = Zr, Hf, Mo, W) performance as a hopeful thermoelectric materials

Significant advancements in nanoscale material efficiency optimization have made it feasible to substantially adjust the thermoelectric transport characteristics of materials. Motivated by the prediction and enhanced understanding of the behavior of two-dimensional (2D) bilayers (BL) of zirconium diselenide (ZrSe2), hafnium diselenide (HfSe2), molybdenum diselenide (MoSe2), and tungsten diselenide (WSe2), we investigated the thermoelectric transport properties using information generated from experimental measurements to provide inputs to work with the functions of these materials and to determine the critical factor in the trade-off between thermoelectric materials. Based on the Boltzmann transport equation (BTE) and Barden-Shockley deformation potential (DP) theory, we carried out a series of investigative calculations related to the thermoelectric properties and characterization of these materials. The calculated dimensionless figure of merit (ZT) values of 2DBL-MSe2 (M = Zr, Hf, Mo, W) at room temperature were 3.007, 3.611, 1.287, and 1.353, respectively, with convenient electronic densities. In addition, the power factor is not critical in the trade-off between thermoelectric materials but it can indicate a good thermoelectric performance. Thus, the overall thermal conductivity and power factor must be considered to determine the preference of thermoelectric materials.

Inside Cover Picture

Herein, we developed a series of conjugated polymers based on an indandione‐terminated quinoidal unit for the application of organic thermoelectric. Owning to the high electron affinity of the quinoidal unit, all polymers showed low‐lying LUMO energy levels below –4.10 eV. By incorporating electron‐withdrawing substituents (F or CN) on the comonomer, the LUMO energy levels of the polymers can be further downshifted to –4.36 eV. The decreased LUMO level is favorable for a high doping efficiency, thus leading to high electrical conductivity and good thermoelectric performance. Among the synthesized polymers, PIQ‐2CNBT with the deepest LUMO level achieved the best thermoelectric performance with a PF of up to 2.14 μW·m–1·K–2. More details are discussed in the article by Deng et al. on page 776—782.image

Strong quartic anharmonicity, ultralow thermal conductivity, high band degeneracy and good thermoelectric performance in Na2TlSb

We employ first-principles calculations combined with self-consistent phonon theory and Boltzmann transport equations to investigate the thermal transport and thermoelectric properties of full-Heusler compound Na2TlSb. Our findings exhibit that the strong quartic anharmonicity and temperature dependence of the Tl atom with rattling behavior plays an important role in the lattice stability of Na2TlSb. We find that soft Tl-Sb bonding and resonant bonding in the pseudocage composed of the Na and Sb atoms interaction is responsible for ultralow κL. Meanwhile, the multi-valley band structure increases the band degeneracy, results in a high power factor in p-type Na2TlSb. The coexistence of ultralow κL and high power factor presents that Na2TlSb is a potential candidate for thermoelectric applications. Moreover, these findings help to understand the origin of ultralow κL of full-Heusler compounds with strong quartic anharmonicity, leading to the rational design of full-Heusler compounds with high thermoelectric performance.

Liquid Metal‐Carbon Fiber Thermocouple Array for Detection of Human Thermal Parameters

AbstractContinuous and accurate measurement of human thermophysical properties has become a vital research field in non‐invasive physiological diagnosis. However, traditional electronic devices have been greatly restricted due to the disadvantages of large volume, heavy weight, and mechanical rigidity. In this work, a kind of fiber‐structured LMs thermocouples composed of LMs fibers and nickel‐coated carbon fibers to solve the dilemma of good thermoelectric performance and sufficient flexibility is synthesized. With high thermoelectric properties as well as flexibility and knittability, the fiber‐structured LMs thermocouples can be assembled into a thermocouple array for multipoint temperature measurement in living organisms. While the nickel‐coated carbon fiber as the electric heating component further endowed the heating function for the fiber‐structured LMs thermocouples array, thus a linear heat source‐pulse heating method is successfully developed for qualitative/quantitative thermophysical parameters measurement (including thermal conductivity, thermal diffusivity, and blood perfusion rate). Collectively, the fiber‐structured LMs thermocouple array has shown promising prospects in human physiological measurement and thermophysical properties measurement.

Thermoelectric Properties of Nickel and Selenium Co-Doped Tetrahedrite.

As the search continues for novel, cheaper, more sustainable, and environmentally friendly thermoelectric materials in order to expand the range of applications of thermoelectric devices, the tetrahedrite mineral (Cu12Sb4S13) stands out as a potential candidate due to its high abundance, low toxicity, and good thermoelectric performance. Unfortunately, as most current thermoelectric materials achieve zTs above 1.0, ternary tetrahedrite is not a suitable alternative. Still, improvement of its thermoelectric performance has been achieved to zTs ≈ 1 via isovalent doping and composition tuning, but most studies were limited to a single doping element. This project explores the effects of simultaneous doping with nickel and selenium in the thermoelectric properties of tetrahedrite. Simulated properties for different stoichiometric contents of these dopants, as well as the measured thermoelectric properties of the correspondent materials, are reported. One of the samples, Cu11.5Ni0.5Sb4S12.5Se0.5, stands out with a high power factor = 1279.99 µW/m·K2 at 300 K. After estimating the thermal conductivity, a zT = 0.325 at 300 K was obtained for this composition, which is the highest for tetrahedrites for this temperature. However, analysis of the weighted mobility shows the presence of detrimental factors, such as grain boundaries, disorder, or ionized impurity scattering, pointing to the possibility of further improvements.

Low lattice thermal conductivities and good thermoelectric performance of hexagonal antiperovskites X(Ba & Sr)3BiN with quartic anharmonicity.

Antiperovskites are a burgeoning class of semiconducting materials that showcase remarkable optoelectronic properties and catalytic properties. However, there has been limited research on their thermoelectric properties. Combining first-principles calculations, self-consistent phonon theory and the Boltzmann transport equation, we have discovered that the hexagonal antiperovskites X(Ba & Sr)3BiN exhibit strong quartic lattice anharmonicity, where the anharmonic vibrations of the light N atoms primarily affect the lattice thermal conductivity (κL) along the c-axis direction. As a result, the lattice thermal conductivities along the a(b)-axis direction are low. At 300 K, the κL values of Ba3BiN and Sr3BiN are only 1.27 W m-1 K-1 and 2.24 W m-1 K-1, respectively. Moreover, near the valence band maximum, the orbitals of the N atoms dominate. This dominance allows Sr3BiN to achieve high power factor under p-type doping, resulting in an impressive thermoelectric figure of merit (ZT) of 0.94 along the c-axis direction at 800 K. In the a(b)-axis direction, at 800 K, n-type doped Ba3BiN exhibits a ZT value of 1.47, surpassing that of traditional thermoelectric materials. Our research elucidates that the hexagonal antiperovskites X(Ba & Sr)3BiN represent a category of potential thermoelectric materials with pronounced anisotropy, low thermal conductivity, and high thermoelectric performance.

Augmented thermoelectric performance of LiCaX (X = As, Sb) Half Heusler compounds via carrier concentration optimization

The present study is focussed on the detailed physical insight into the structural, thermal, and dynamical properties of 8-valence electron Half Heusler (HH) compounds LiCaX (X = As, Sb) using Density functional theory. The thermal and dynamic stabilities of the compounds are assessed via ab-initio molecular dynamic simulations and phonon dispersion calculations, respectively. The Tran-Blaha modified Becke Johnson potential is used to accurately predict the band gap of investigated compounds. It is found that they are indirect band gap semiconductors with band gaps of 2.52 eV (LiCaAs) and 2.09 eV (LiCaSb). The transport parameters are obtained for p-type and n-type doping at temperatures ranging from 300 K to 800 K by solving the Boltzmann Transport equation. The deformation potential theory is employed to calculate the temperature dependent relaxation time for both compounds. The results of the various thermoelectric parameters obtained using actual values of time-dependent relaxation time are compared with that calculated under constant relaxation time approximation. The maximum power factor is 10.95 × 1011 (4.99 × 1011) Wm−1K−2s−1 for p-type (n-type) LiCaAs and 12.53 × 1011 (5.30 × 1011) Wm−1K−2s−1 for p-type (n-type) LiCaSb at optimized carrier concentration. The obtained low lattice thermal conductivities for LiCaSb (0.66 Wm−1K−1) and LiCaAs (0.88 Wm−1K−1) are explicated it in terms of different phonon modes. The Figure of Merit at 800 K for p-type (n-type) LiCaAs is as high as 0.90 (0.73) and 0.93 (0.84) for LiCaSb at optimum carrier concentration ∼1020 cm−3 (∼1019 cm−3), which has been experimentally realized in other 8-valence electron Li-based HH compounds. The good thermoelectric performance of p-type LiCaX in comparison to n-type suggests that p-type LiCaX alloys are viable candidates for high temperature energy harvesting applications.

Probing the Effect of MWCNT Nanoinclusions on the Thermoelectric Performance of Cu3SbS4 Composites.

Recently, copper-based chalcogenides, especially sulfides, have attracted considerable attention due to their inexpensive, earth-abundance, nontoxicity, and good thermoelectric performance. Cu3SbS4 is one such kind with p-type conductivity and high phase stability for potential medium-temperature applications. In this article, the effect of a multiwalled carbon nanotube (MWCNT) on the thermoelectric parameters of Cu3SbS4 is studied. A facile synthesis route of mechanical alloying (MA), followed by hot pressing (HP) was utilized to achieve dense and fine-grain samples. Adding the optimal amount of MWCNT nanoinclusions in Cu3SbS4 enhanced the Seebeck coefficient by carrier energy filtering and reduced the thermal conductivity by strong phonon scattering mechanisms. This synergistic optimization helped achieve the maximum figure of merit (ZT) of 0.43 in the 3 mol % MWCNT nanoinclusion composite sample, which is 70% higher than the pristine Cu3SbS4 at 623 K. In addition, enhancement in mechanical stability is observed with the increasing nanoinclusion concentration. Dispersion strengthening and grain boundary hardening mechanisms help improve mechanical stability in the nanocomposite samples. Apart from the enhanced mechanical stability, our study highlights that the incorporation of multiwalled CNT nanoinclusions boosted the thermoelectric performance of Cu3SbS4, and the same strategy can be extended to other next-generation and conventional thermoelectric materials.

Achieving metal-like malleability and ductility in Ag2Te1-xSx inorganic thermoelectric semiconductors with high mobility

Inorganic semiconductor Ag2Te1-x S x has been recently found to exhibit unexpected plastic deformation with compressive strain up to 30%. However, the origin of the abnormal plasticity and how to simultaneously achieve superb ductility and high mobility are still elusive. Here, we demonstrate that crystalline/amorphous Ag2Te1-x S x (x= 0.3, 0.4, and 0.5) composites can exhibit excellent compressive strain up to 70% if the monoclinic Ag2Te phase, which commonly exists in the matrix, is eliminated. Significantly, an ultra-high tensile elongation reaching 107.3% was found in Ag2Te0.7S0.3, which is the highest one yet reported in the system and even surpasses those achieved in some metals and high-entropy alloys. Moreover, high mobility of above 1000cm2 V-1 s-1 at room temperature and good thermoelectric performance are simultaneously maintained. A modified Ashby plot with ductility factor versus carrier mobility is thereby proposed to highlight the potential of solid materials for applications in flexible/wearable electronics.