Room Temperature Resistivity Research Articles

Composite Polymer Electrolytes for Lithium Batteries

AbstractThe flexible and less flammable solid polymer electrolytes are attractive candidates for high specific energy density lithium batteries. However, the use of polymer electrolytes in rechargeable batteries for EVs is hindered because of their low lithium‐ion conductivity at room temperature and lithium dendrite formation during lithium deposition at high current density. To improve the room temperature conductivity of polymer electrolytes, composite lithium‐ion conductors consisting of polymer and ionic liquids or inorganic solid lithium ion conductors have been examined over the past two decades. The polymer electrolyte with ionic liquid showed ionic conductivity of more than 10−4 S cm−1at room temperature, but lithium dendrite‐free composite electrolytes have not yet been reported at room temperature and a high current density. The flexible composite electrolytes of polymers and lithium‐ion conductive solid electrolytes showed high ionic conductivity of more than 2×10−4 S cm−1and no dendrite short‐circuit was observed at room temperature and 1.0 mA cm−1for long cycling. The suppression of lithium dendrite formation in the composite electrolyte is due to the formation of a stable interface layer between the lithium electrode and composite electrolyte. At present, no room temperature all‐solid‐state batteries have been developed with performance comparable to conventional lithium‐ion batteries with liquid electrolytes. One of the disadvantage of the lithium batteries with the composite polymer electrolyte is higher mass of the electrolyte than that of a liquid electrolyte with a porous separator. The specific energy density of the batteries depends on the thickness of the electrolyte and the specific area capacity. At present, the thickness of the polymer composite electrolytes is in a range of 50–200 μm. The specific energy density of the lithium battery with a 100 μm thick composite electrolyte is 430 Wh kg−1at 10 mAh cm−2, which is 1.4 times higher than that of the conventional Li‐ion battery. A high specific area capacity battery with a thin polymer composite electrolyte should be developed to obtain a high energy density battery. We are anxiously expecting a mechanically stable composite polymer electrolyte thin film of less than 100 μm thick with high Li‐ion conductivity more than 10−3 S cm−1at room temperature and low interface resistance with Li electrode. The addition of small amount of a low molecular weight additive into the composite electrolytes is effective to improve the interface resistance between the lithium electrode and composite electrolyte, which results in no dendrite formation at high current density and room temperature.

Room temperature spin-orbit torque efficiency in sputtered low-temperature superconductor δ -TaN

In the course of searching for promising topological materials for applications in future topological electronics, we evaluated spin-orbit torques (SOTs) in high-quality sputtered \ensuremath{\delta}-TaN/${\mathrm{Co}}_{20}{\mathrm{Fe}}_{60}{\mathrm{B}}_{20}$ devices through spin-torque ferromagnetic resonance (ST-FMR) and spin pumping measurements. From the ST-FMR characterization we observed a significant linewidth modulation in the magnetic ${\mathrm{Co}}_{20}{\mathrm{Fe}}_{60}{\mathrm{B}}_{20}$ layer attributed to the charge-to-spin conversion generated from the \ensuremath{\delta}-TaN layer. Remarkably, the spin-torque efficiency determined from ST-FMR and spin pumping measurements is as large as $\mathrm{\ensuremath{\Theta}}=$ 0.034 and 0.031, respectively. These values are over two times larger than for \ensuremath{\alpha}-Ta, but almost five times lower than for \ensuremath{\beta}-Ta, which can be attributed to the low room temperature electrical resistivity $\ensuremath{\sim}74\phantom{\rule{0.16em}{0ex}}\ensuremath{\mu}\mathrm{\ensuremath{\Omega}}\phantom{\rule{0.16em}{0ex}}\mathrm{cm}$ in \ensuremath{\delta}-TaN. A large spin diffusion length of at least $\ensuremath{\sim}8\phantom{\rule{0.16em}{0ex}}\mathrm{nm}$ is estimated, which is comparable to the spin diffusion length in pure Ta. Comprehensive experimental analysis, together with density functional theory calculations, indicates that the origin of the pronounced SOT effect in \ensuremath{\delta}-TaN can be mostly related to a significant contribution from the Berry curvature associated with the presence of a topically nontrivial electronic band structure in the vicinity of the Fermi level (${E}_{\mathrm{F}}$). Through additional detailed theoretical analysis, we also found that an isostructural allotrope of the superconducting \ensuremath{\delta}-TaN phase, the simple hexagonal structure \ensuremath{\theta}-TaN, has larger Berry curvature, and that, together with expected reasonable charge conductivity, it can also be a promising candidate for exploring a generation of spin-orbit torque magnetic random access memory as cheap, temperature stable, and highly efficient spin current source.

EFFECT OF LATTICE MISMATCH ON THE MICROSTRUCTURE AND ELECTRICAL PROPERTIES OF LaNiO3 CONDUCTIVE FILMS

In this work, we prepared LaNiO3 (LNO) and Au-LaNiO3 (Au-LNO) films using sol–gel multilayer coating method. The effects of lattice mismatch on the microstructure and electrical properties of the films were investigated by choosing different single-crystal substrate. XRD, SEM, and AFM results showed the high quality of LNO and Au-LNO films, indicating the successful epitaxial growth of the films on the single-crystal substrates. The room temperature resistivity of LNO films increased with the increase of lattice mismatch while different tendency was observed in Au-LNO films, suggesting that different mechanisms prevailed in the LNO and Au-LNO films. Both the transport behavior and the residual resistivity ratio were checked to explore the relationship between the lattice mismatch and the electrical properties of the films. Strain and defect concentration were proposed as the predominating factors for the changes in the resistivity of LNO and Au-LNO films under the influence of lattice mismatch.

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.

Magnetoresistive behaviour of ternary Cu-based materials processed by high-pressure torsion

Severe plastic deformation using high-pressure torsion of ternary Cu-based materials (CuFeCo and CuFeNi) was used to fabricate bulk samples with a nanocrystalline microstructure. The goal was to produce materials featuring the granular giant magnetoresistance effect, requiring interfaces between ferro- and nonmagnetic materials. This magnetic effect was found for both ternary systems; adequate subsequent annealing had a positive influence. The as-deformed states, as well as microstructural changes upon thermal treatments, were studied using scanning electron microscopy and X-ray diffraction measurements. Deducing from electron microscopy, a single-phase structure was observed for all as-deformed samples, indicating the formation of a supersaturated solid solution. However, judging from the presence of the granular giant-magnetoresistive effect, small ferromagnetic particles have to be present. The highest drop in room temperature resistivity (2.45% at 1790 kA/m) was found in Cu62Fe19Ni19 after annealing for 1 h at 400 °C. Combining the results of classical microstructural studies and magnetic measurements, insights into the evolution of ferromagnetic particles are accessible.

Infrared plasmons in ultrahigh conductive PdCoO2 metallic oxide

PdCoO2 layered delafossite is the most conductive compound among metallic oxides, with a room-temperature resistivity of nearly 2,mu Omega ,{{{{{rm{cm}}}}}}, corresponding to a mean free path of about 600 Å. These values represent a record considering that the charge density of PdCoO2 is three times lower than copper. Although its notable electronic transport properties, PdCoO2 collective charge density modes (i.e. surface plasmons) have never been investigated, at least to our knowledge. In this paper, we study surface plasmons in high-quality PdCoO2 thin films, patterned in the form of micro-ribbon arrays. By changing their width W and period 2W, we select suitable values of the plasmon wavevector q, experimentally sampling the surface plasmon dispersion in the mid-infrared electromagnetic region. Near the ribbon edge, we observe a strong field enhancement due to the plasmon confinement, indicating PdCoO2 as a promising infrared plasmonic material.

Excellent positive temperature coefficient behavior and electrical reproducibility of HDPE/(TiC-CB) composites

The high-density polyethylene/(titanium carbide--carbon black) (HDPE/(TiC-CB) composites were prepared by meltingblendprocess. Microstructure, room temperature resistivity, positive temperature coefficient (PTC) behavior and electrical reproducibility of composites were investigated. Results show that adding 3.0 vol% CB was in favor of reducing the room temperature resistivity of HDPE/(TiC-CB) composites, and leading to obtain high PTC intensity (the ratio of maximum resistivity to room temperature resistivity is defined as the PTC intensity). When the content of conductive fillers TiC was 32.0 vol% and CB was 3.0 vol%, the room temperature resistivity of composites was 0.8 Ω.m and PTC intensity reached 7.0, which is similar to the composites with 45.0 vol% TiC individually. The reduction of the inorganic material TiC facilitates the more flexibility of the composites, and the effect of PTC was still stability after several heating cycles. When the content of CB was more than 5.0 vol%, the room temperature resistivity was slightly reduced. However, the PTC intensity dropped below 3.7 abruptly. The micrographs of scanning electron microscopy (SEM) indicated that the CB had greatly influence on the formation of the electric conduction channel in the matrix.

Effect of hybridization in PdAlY-(Ni/Au/Ir) metallic glasses thin films on electrical resistivity

Thin film metallic glasses (MGs) are promising materials for electronic applications. While the transport properties of MGs are composition dependent, the influence of hybridization on the resistivity has not been investigated systematically. We implement a correlative experimental and computational approach utilizing thin film deposition, electrical resistivity measurements, synchrotron X-ray diffraction and ab initio calculations to explore the relationship between the fraction of hybridized bonds present in PdAlY-M glasses with M=Ir,Au,Ni, where the electrical behavior is dominated by d-electrons. The strong bonds hybridization in PdAlY-Ir yields a high resistivity of 175 µΩm, while the weakly hybridized bonds in PdAlY-M MGs (M = Au, Ni) result in lower resistivities of 114 and 92 µΩm, respectively. We propose that an increase in the amount of anti-bonding states close to the Fermi level yields an increased room temperature resistivity.

Lamination process of second generation high temperature superconducting tape at Shanghai Superconductor Technology

As the second generation high temperature superconducting (HTS) tape enters the stage of commercialization and mass production, it has been successfully applied in several power and magnet devices. Different application scenarios also put forward different requirements for the electrical and mechanical properties of the HTS tape. This paper focuses on introducing the post-processing treatments of HTS tape, primarily copper plating and lamination. By preparing typical samples, the properties of copper-plated tapes and laminated tapes have been experimentally compared. The results show that under the condition of sufficient liquid nitrogen flow, the steady-state over-current tolerance of copper-laminated tape is significantly better than that of stainless steel-laminated and copper-plated tapes. At the same room temperature resistance, the over-current impact tolerance of stainless steel-laminated tape is 2–3 times that of copper-plated tape; the maximum transient current beared by the tapes reached 3896 A when they were put under shock for 8 ms, which has significant advantages in the application of resistive fault current limiter. At 77 K, yield strength Rp0.2 of the three types of superconducting tapes are > 1100 MPa for stainless steel-laminated tape, 645–1037 MPa for copper-plated tape and < 500 MPa for copper-laminated tape. The critical tensile stress of stainless steel laminated-tape is higher than that of copper-plated tape and copper-laminated tape. The tape reinforced structure described in this paper can provide a helpful reference for future design and manufacture of superconducting applications in power and magnet industries.

Structural and Electrical Studies of Boric Acid Doped Cadmium Oxide Thin Film by JNSP Technique for Optoelectronic Applications

The present work deals with preparation and characterization of boric acid (b) dopped cdo thin films by the jet nebulizer spray pyrolysis technique at optimized temperature 450°C. Boric acid doped cdo thin films were prepared by jet nebulizer spray pyrolysis technique with different wt% of boric acid (x=0, 0.5,2.5, 4). The xrd pattern of various weight percentage boric acid dopped cdo thin films show the polycrystalline nature with cubic structure. At room temperature, the electrical conductivity of the prepared films increases with 4Wt% of 2.32x10-3 S/cm. The plot of voltage versus current as a function of temperature (RT-30°C) indicates the ohmic behavior of the films. Moreover, significant optoelectronic applications are cadmium oxide dopped with boric acid thin films at room temperature electrical resistivity is in the order of 101Ω cm which is low enough to be a good supercapacitor electrode material.

Disordered MgB[formula omitted] superconductor critical temperature modeling through regression trees

Magnesium boride superconductors are promising candidates in high energy physics applications. These superconductors have several advantages as compared to other high temperature superconductors, such as the absence of weaklinks in grain boundaries, abundant availability of raw materials, simple wire fabrication process, and increased isotropy in microstructure and material performance. Critical temperature, Tc, is the most critical parameter in superconductor characterizations. Various factors have impacts on Tc, including the chemical doping, irradiation, and synthesis conditions. It has been shown that disorders in the crystal structure lead to changes in normal state resistivities and Tc, which are correlated with each other. Here, the regression tree model is developed to predict Tc of disordered magnesium boride superconductors through room temperature resistivities. This modeling approach manifests a high degree of accuracy and stability, contributing to efficient low-cost estimations of critical temperature and understandings of disorder and superconductivity in MgB2 superconductors.

Epitaxial Bi2Sr2CuOu y thin films as p-type transparent conductors

Development of p-type transparent conducting thin films is tireless due to the trade-off issue between optical transparency and conductivity. The rarely concerned low normal state resistance makes Bi-based superconducting cuprates the potential hole-type transparent conductors, which have been realized in Bi2Sr2CaCu2O y thin films. In this study, epitaxial superconducting Bi2Sr2CuO y and Bi2Sr1.8Nd0.2CuO y thin films with superior normal state conductivity are proposed as p-type transparent conductors. It is found that the Bi2Sr1.8Nd0.2CuO y thin film with thickness 15 nm shows an average visible transmittance of 65% and room-temperature sheet resistance of 650 Ω/sq. The results further demonstrate that Bi-based cuprate superconductors can be regarded as potential p-type transparent conductors for future optoelectronic applications.

Bandgap tuning, high electrical conductivity, and room-temperature ferromagnetism in La- and V-doped SrSnO3 epitaxial films

In this study, La- and V-doped SrSnO3 epitaxial films were fabricated via pulsed laser deposition, and the effects of doping on the structure and physical properties of films were systematically investigated. Detailed x-ray diffraction characterization demonstrates that the lattice parameters of V-doped SrSnO3 (SrSn1−xVxO3, x = 0–1, SSVO) films decrease gradually as the V content increases. The optical bandgap first increases from 4.43 to 4.56 eV and then decreases to 3.31 eV with the increasing V content. Density functional theory calculations indicate that the strong hybridization between Sn 5s and V 3d orbitals causes an initial expansion of the bandgap. Doping SSVO films with 5% La greatly improves the electrical conductivity. Hall-effect measurements show that the (La0.05Sr0.95)VO3 film has the lowest room-temperature resistivity of 0.05 mΩ cm and correspondingly the largest carrier density of 1.79 × 1022 cm−3. Ferromagnetism in SrSn1−xVxO3 films is highly dependent on V concentration at room-temperature, and the origin of ferromagnetism may be explained by the bound magnetic polaron model.

Investigation of PTCR characteristics in Sm2O3-doped BaTiO3-based chip-type ceramics prepared in a reducing atmosphere

In this paper, we investigated the influence of cooling rates on electrical properties and positive temperature coefficient of resistance (PTCR) effect of (Ba1.22−xSmx)TiO3 + 0.007 mol SiO2 (BTS) ceramics, which were fired at 1200∘C for 30 min in a reducing atmosphere and then reoxidized at 700–800∘C for 1 h. The results showed that the room-temperature (RT) resistivity and the resistance jump of the chip-type BTS ceramics increased with an increase in the cooling rate. Furthermore, the RT resistivity of the BTS specimens gradually decreased at first and then increased with increasing donor-doping concentration. In addition, the influence of cooling rates on the microstructure of ceramics was also investigated.

Growth of highly conducting MoS2-xNx thin films with enhanced 1T' phase by pulsed laser deposition and exploration of their nanogenerator application

SummaryHigh-quality growth of MoS2-xNx films is realized on single-crystal c-Al2O3 substrates by the pulsed laser deposition (PLD) in ammonia rendering highly stable and tunable 1Tʹ/2H biphasic constitution. Raman spectroscopy reveals systematic enhancement of 1Tʹ phase component due to the incorporation of covalently bonded N-doping in MoS2 lattice, inducing compressive strain. Interestingly, the film deposited at 300 mTorr NH3 shows ∼80% 1Tʹ phase. The transport measurements performed on MoS2-xNx films deposited at 300 mTorr NH3 display very low room temperature resistivity of 0.03 mΩ-cm which is 100 times enhanced over the undoped MoS2 grown under comparable conditions. A triboelectric nanogenerator (TENG) device containing biphasic MoS2-xNx film as an electron acceptor exhibits a clear enhancement in the output voltage as compared to the pristine MoS2. Device architecture, p-type N doping in MoS2 lattice, favorably increased work-function, multiphasic component of MoS2, and increased surface roughness synergistically contribute to superior TENG performance.

Extreme Learning Machine Approach to Modeling the Superconducting Critical Temperature of Doped MgB2 Superconductor

Magnesium diboride (MgB2) superconductor combines many unique features such as transparency of its grain boundaries to super-current flow, large coherence length, absence of weak links and small anisotropy. Doping is one of the mechanisms for enhancing these features, as well as the superconducting critical temperature, of the compound. During the process of doping, the MgB2 superconductor structural lattice is often distorted while the room temperature resistivity, as well as residual resistivity ratio, contributes to the impurity scattering in the lattice of doped samples. This work develops three extreme learning machine (ELM)-based empirical models for determining MgB2 superconducting critical temperature (TC) using structural distortion as contained in lattice parameters (LP) of doped superconductor, room temperature resistivity (RTR) and residual resistivity ratio (RRR) as descriptors. The developed models are compared with nine different existing models in the literature using different performance metrics and show superior performance over the existing models. The developed SINE-ELM-RTR model performs better than Intikhab et al. (2021)_linear model, Intikhab et al. (2021)_Exponential model, Intikhab et al. (2021)_Quadratic model, HGA-SVR-RRR(2021) model and HGA-SVR-CLD(2021) model with a performance improvement of 32.67%, 29.56%, 20.04%, 8.82% and 13.51%, respectively, on the basis of the coefficient of correlation. The established empirical relationships in this contribution will be of immense significance for quick estimation of the influence of dopants on superconducting transition temperature of MgB2 superconductor without the need for sophisticated equipment while preserving the experimental precision.

Effect of disordered nanoporosity on electrical and thermal properties of layered Ca3Co4O9 films

Independently controlling electronic and thermal transport in solids is a challenge, because these properties are coupled. Here, we show that disordered nanoporosity in Ca3Co4O9 thin films can decrease the thermal conductivity without significantly hampering electronic transport. Scanning thermal microscopy was used to determine the out-of-plane thermal conductivity and estimate the in-plane values. Nanoporous Ca3Co4O9 films exhibit a thermal conductivity of 0.82 W m−1 K−1, which is nearly twofold lower than that obtained from nonporous Ca3Co4O9 films. Nanoporous Ca3Co4O9 exhibit a room-temperature electrical resistivity of 4 mΩ cm, which is comparable to polycrystalline Ca3Co4O9 and twice that reported for single-crystal Ca3Co4O9. Our results suggest that controlling nanoporosity and their degree of disorder can offer a means of decoupling electrical and thermal properties in materials.

Ionic Liquid Gating Control of Oxygen Vacancies in the La0.8Ba0.2MnO3 Ultrathin Films

In this work, we show ionic liquid field-effect of La0.8Ba0.2MnO3 (LBMO) untrathin films prepared by the sol-gel method. When applying a positive gate voltage (V g) in vacuum, it is found that the film resistivity continuously increases tenfold within hours or minutes depending on the magnitude of V g, accompanied with disappearance of the low-temperature metallic transport behavior. In contrast, the film resistivity changes little in air or under a negative applied V g. Such a difference reveals that the increased resistivity is related to the oxygen depletion in the films under the positive V g, especially at the grain boundaries. After removing the positive V g in vacuum, the room-temperature resistivity begins to fall off and the low-temperature metallic state is partially restored in several tens hours, suggesting oxygen diffusion from the relatively oxygen-rich grains to the seriously oxygen-deficient grain boundaries. Furthermore, the oxygen content in the oxygen-deficient films can be almost fully restored in ten minutes by external annealing (200 °C) or Joule self-heating (21 mA) the films in air. These experimental findings provide an additional method in tuning oxygen vacancies in transition-metal oxide films.

Progress on Second-Generation High-Temperature Superconductor Tape Targeting Resistive Fault Current Limiter Application

The resistive superconducting fault current limiter is well known for its simple structure and outstanding current-limiting effect, and it is broadly applied in power grid systems. The second-generation high-temperature superconductor (HTS) tape, of higher structural strength and greater room-temperature resistance, is well suited for application in resistive superconducting fault current limiters. The quenching caused by overcurrent in the HTS tape is a complexed coupling effect of several physical factors. The tape structure and properties directly impact the ultimate HTS tape’s quench performance. In this study, various SS316-laminated HTS tapes, of different critical currents, room-temperature resistances, and masses, were prepared. The pulse impact parameters of the various tape samples were measured using the RLC high-current impact test platform. By analyzing the resultant data, a quantitative assessment methodology to measure a tape’s tolerance toward impact was developed. The dependence of the HTS tape’s tolerance toward impact on its critical current, room-temperature resistance, and mass was studied. This provides numerical guidance on HTS material selection for resistive superconducting fault current limiters.

Infrared Absorption and Its Sources of CdZnTe at Cryogenic Temperature

To reveal the causes of infrared absorption in the wavelength region between electronic and lattice absorptions, we measured the temperature dependence of the absorption coefficient of p-type low-resistivity (sim 10^2~ Omega mathrm{cm}) CdZnTe crystals. We measured the absorption coefficients of CdZnTe crystals in four wavelength bands (lambda =6.45, 10.6, 11.6, 15.1~mu m) over the temperature range of T=8.6-300 K with an originally developed system. The CdZnTe absorption coefficient was measured to be alpha =0.3-0.5 mathrm{cm}^{-1} at T=300 K and alpha =0.4-0.9 mathrm{cm}^{-1} at T=8.6 K in the investigated wavelength range. With an absorption model based on transitions of free holes and holes trapped at an acceptor level, we conclude that the absorption due to free holes at T=150-300 K and that due to trapped-holes at T<50 K are dominant absorption causes in CdZnTe. We also discuss a method to predict the CdZnTe absorption coefficient at cryogenic temperature based on the room-temperature resistivity.