Plane Temperature Research Articles

Fabrication and Characterization of LiNi1/3Mn1/3Co1/3O2/Li0.6La0.4TiO3/Li4Ti5O12 Full Cell All-Solid-State Thin Film Li-Ion Batteries for Energy Applications

Recent days, natural calamities caused by the global warming and climate changes are major concern for the entire globe and there is a pressing need to address such issues to save the mankind from further havoc and devastation. To reduce the carbon emission, countries are shifting dramatically towards renewable sources for their energy needs for their day-to-day life. Li ion batteries are in the forefront of the battle towards the sustainable growth and development due to their high energy density and renewable in nature. In the present case, we report on development of thin film based all-solid-state batteries (ASSB) for energy applications. LiNi1/3Mn1/3Co1/3O2 (NMC), Li0.6La0.4TiO3 (LLTO) and Li4Ti5O12 (LTO) materials are employed as a cathode, solid electrolyte and anode layers for fabricating a full cell all-solid-state thin film batteries. All the layers are fabricated employing RF sputtering technique. Before fabricating the full cell, individual layers are fabricated and their electrochemical and/or ionic conductivity properties are explored. Li0.6La0.4TiO3 solid electrolyte thin films are seen to exhibit room temperature in-plane ionic conductivity in the order of 10-3 S/cm. NMC thin film with the thickness of 100 nm exhibits specific capacity of 91 µAh/cm2 and the redox peaks at 3.8 V and 3.5 V. LTO anode thin films shows the specific capacity close to 100 mAh/cm2and the redox peaks around 1.5 V. XRD pattern of NMC/LLTO/LTO full cell shows the diffraction peaks corresponding to all the three layers. Cross-sectional scanning electron microscope (SEM) image indicates the uniform coating and presence of all the layers. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) along with the energy dispersive X-ray is employed to image the cross-sectional details and the elements present in each layer of the full cell all-solid-state thin film battery. Impedance spectroscopy was employed to calculate the total conductivity of the fabricated full cell. Obtained results indicates that the full cell NMC/LLTO/LTO thin film batteries can be fabricated employing a sputtering technique for the energy applications. Figure 1

Domain-dependent strain and stacking in two-dimensional van der Waals ferroelectrics

Van der Waals (vdW) ferroelectrics have attracted significant attention for their potential in next-generation nano-electronics. Two-dimensional (2D) group-IV monochalcogenides have emerged as a promising candidate due to their strong room temperature in-plane polarization down to a monolayer limit. However, their polarization is strongly coupled with the lattice strain and stacking orders, which impact their electronic properties. Here, we utilize four-dimensional scanning transmission electron microscopy (4D-STEM) to simultaneously probe the in-plane strain and out-of-plane stacking in vdW SnSe. Specifically, we observe large lattice strain up to 4% with a gradient across ~50 nm to compensate lattice mismatch at domain walls, mitigating defects initiation. Additionally, we discover the unusual ferroelectric-to-antiferroelectric domain walls stabilized by vdW force and may lead to anisotropic nonlinear optical responses. Our findings provide a comprehensive understanding of in-plane and out-of-plane structures affecting domain properties in vdW SnSe, laying the foundation for domain wall engineering in vdW ferroelectrics.

The effect of fiber preform configuration on in-plane compressive behavior of high porosity needled carbon/carbon composites in elevated temperature environment

The in-plane compressive behavior of the high porosity needled carbon/carbon (C/C) composites can be used to examine the interlaminar state and the material integrity. The room and elevated temperature in-plane compressive experiments of the high porosity needled C/C composites were conducted to study the effect of local fiber configuration state on the failure modes and damage mechanisms combining with the scanning electron microscope (SEM) and micro-computed tomography (Micro-CT) observation. The porosity was also determined by processing Micro-CT images, which was used to calculate the mechanical properties of constituents. The refined finite element (FE) model considering explicitly the distribution of needling punched regions of the real compressive specimen was established to reproduce the damage and failure process component materials in the high porosity needled C/C composites during the experiment at elevated temperature. The effect of needling parameters, such as the needling depth and the thickness ratio between fiber net layer and non-woven cloth layer, on the compressive mechanical properties of the high porosity needled C/C composites was studied using the parametric FE model. The variation curves of the compressive strength with these needling parameters were obtained, which could guide to choose the proper high porosity needled C/C composites for manufacturing the lightweight thermal protection tile after introducing the oxidation resistant ceramic matrix.

The emergence of high room temperature in-plane and out-of-plane magnetostriction in polycrystalline CoFe2O4 film

The polycrystalline CoFe2O4 (CFO) film on cantilever substrate of silicon was grown using pulsed laser deposition (PLD) method and investigated its in-plane and out-of-plane magnetostrictive strain at room temperature (300 K) using the indigenous optical Cantilever Beam Magnetometer (CBM). The film shows a high compressive magnetostrictive strain of ‒ 387 ppm and ‒ 708 ppm for in-plane and out-of-plane configurations, respectively. Considerably, the magnetostrictive strain loops (λ‒H) possess a certain degree of hysteresis with a symmetric butterfly shape. The origin of large compressive magnetostriction of CFO film is attributed to the non-180° domain wall motion followed by 90° domain rotation. The large values of saturation magnetostrictive strain make CFO film a suitable candidate in sensor design for different purposes.

Electronic band structure of iridates.

In this review, an attempt has been made to compare the electronic structures of various 5d iridates (iridium oxides), with an effort to note the common features and differences. Both experimental studies, especially angle-resolved photoemission spectroscopy (ARPES) results, and first-principles band structure calculations have been discussed. This brings to focus the fact that the electronic structures and magnetic properties of the high-Z 5d transition iridates depend on the intricate interplay of strong electron correlation, strong (relativistic) spin-orbit coupling, lattice distortion, and the dimensionality of the system. For example, in the thin film limit, SrIrO3 exhibits a metal-insulator transition that corresponds to the dimensionality crossover, with the band structure resembling that of bulk Sr2IrO4.

Phonon Dynamics and Transport Properties of Copper Thiocyanate and Copper Selenocyanate Pseudohalides.

The phonon transport properties of CuSCN and CuSeCN have been investigated using the density functional theory and semiclassical Boltzmann transport theory. The Perdew–Burke–Ernzerhof functional shows an indirect (direct) electronic band gap of 2.18 eV (1.80 eV) for CuSCN (CuSeCN). The calculated phonon band structure shows that both compounds are dynamically stable. The Debye temperature of the acoustic phonons is 122 and 107 K for CuSCN and CuSeCN, respectively. The extended in-plane bond lengths as compared to the out-of-plane bond lengths result in phonon softening and hence, low lattice thermal conductivity. The calculated room temperature in-plane (out-of-plane) lattice thermal conductivity of CuSCN and CuSeCN is 2.39 W/mK (4.51 W/mK) and 1.70 W/mK (3.83 W/mK), respectively. The high phonon scattering rates in CuSeCN give rise to in-plane low lattice thermal conductivities. The room-temperature Grüneisen parameters of CuSCN and CuSeCN are found to be 0.98 and 1.08, respectively.

Two-dimensional carbon allotropes with tunable direct band gaps and high carrier mobility

Using first-principles calculations, two sp2 + sp3-hybridized two-dimensional (2D) carbon allotropes with stable orthorhombic structures are predicted in this work. Both structures are composed of tetra-, penta-, and hexa-rings of carbon atoms, known as TPH-I carbon and TPH-II carbon. We demonstrate that they can be obtained from penta-graphene by the Stone-Wales (SW) transformation. TPH-I carbon has an inherent direct band gap of 2.704 eV, while TPH-II carbon has a quasi-direct band gap of 2.361 eV. After applying uniaxial strain, TPH-I and TPH-II carbon will have tunable direct band gaps in the range of 2.441–2.812 eV and 2.468–2.7562 eV, respectively. Their electrons and holes mobilities are found to be anisotropic. TPH-I carbon shows extraordinary room temperature in-plane electron mobility of ~7.9 × 104 cm2 V−1 s−1 and TPH-II carbon shows high hole mobility of ~1.5 × 104 cm2 V−1 s−1. Both novel carbon sheets exhibit strong absorption of visible light. And their intrinsic anisotropic optical properties allow optical determination of the crystalline orientation. In addition, TPH-I carbon is a potential photocatalyst for the water splitting reaction.

Influence of dynamic temperature variation and inplane varying loads over post-buckling and free vibration analysis of sandwich composite beam

In this study, nonlinear post-buckling and free vibration analysis of shape memory polymer sandwich composite (SMPSC) under dynamic temperature variation is performed. For the analysis, simplified Co continuity based on higher-order shear deformation theory (HSDT) has been adopted to perform finite element analysis (FEA). Numerical solutions are obtained by iterative Newton–Raphson method considering Von-Karman nonlinear kinematics. Material properties of SMPSC, with Shape Memory Polymer (SMP) as matrix and carbon fiber as reinforcements, have been calculated by theory of volume averaging. The effect of dynamic temperature variation and axial variable inplane loadings (AVIL) on SMPC and SMPSC has been evaluated for various parameters such as beam thickness ratio, layer variation, boundary conditions (BCs), position of core, thickness of core in sandwich structures for the first time. Apart from these, this study also clearly reveals the difference in magnitude of buckling and free vibration parameters between the shape memory polymer composites (SMPC) and SMPSC, before and after glass transition region of material.

Anisotropic ion transport in 2D polymer single crystal-based solid polymer electrolytes

Solid polymer electrolytes (SPEs) are promising for the next-generation all-solid-state lithium metal battery (LMB) applications. The effect of semicrystalline structure on ion transport is two-fold: the crystalline domains provide a tortuous diffusion pathway (structural effect) while the tethered chains can cause sluggish ion diffusion (dynamic effect). These two effects are intertwining in a bulk semicrystalline SPE system. In this work, we fabricate a series of polymer single crystal (PSC)-based SPEs by infiltrating lithium bis(trifluoromethylsulfonyl) imide (LiTFSI) into poly(ethylene oxide) (PEO) PSC films. The obtained SPE films show anisotropic conducting behavior with the in-plane conductivity being one to three orders of magnitudes greater than the through-plane conductivity, which can be attributed to the PSC-guided ion transport. The room temperature in-plane conductivity of the PSC SPE can be comparable to its amorphous counterpart, indicating that the tortuosity effect plays a major role in the reduced ionic conductivity of semicrystalline SPEs. PSC-LiTFSI superstructure is observed in the PSC SPEs due to selective perforation of the crystalline PEO lamellae by LiTFSI salts. This work demonstrates the importance of the crystalline morphology on the ion transport in semicrystalline SPEs.

Pressure tuning of structural and magnetic transitions in EuAg4As2

We report temperature dependent measurements of ambient pressure specific heat, magnetic susceptibility, anisotropic resistivity and thermal expansion as well as in-plane resistivity under pressure up to 20.8 kbar on single crystals of EuAg$_4$As$_2$. Based on thermal expansion and in-plane electrical transport measurements at ambient pressure this compound has two, first order, structural transitions in 80 - 120 K temperature range. Ambient pressure specific heat, magnetization and thermal expansion measurements show a cascade of up to seven transitions between 8 and 16 K associated with the ordering of the Eu$^{2+}$ moments. In-plane electrical transport is able to detect more prominent of these transitions: at 15.5, 9.9, and 8.7 K as well as a weak feature at 11.8 K at ambient pressure. Pressure dependent electrical transport data show that the magnetic transitions shift to higher temperatures under pressure, as does the upper structural transition, whereas the lower structural transition is suppressed and ultimately vanishes. A jump in resistivity, associated with the upper structural transition, decreases under pressure with an extrapolated disappearance (or a change of sign) by 30-35 kbar. In the 10 - 15 kbar range a kink in the pressure dependence of the upper structural transition temperature as well as the high and low temperature in-plane resistivities suggest that a change in the electronic structure may occur in this pressure range. The results are compared with the literature data for SrAg$_4$As$_2$.

Steady state charge conduction through solution processed liquid crystalline lanthanide bisphthalocyanine films

In-plane electrical characteristics of non-peripherally octyl(C[Formula: see text]H[Formula: see text]- and hexyl(C[Formula: see text]H[Formula: see text]-substituted liquid crystalline (LC) double decker lanthanide bisphthalocyanine (LnPc[Formula: see text] complexes with central metal ions lutetium (Lu), and gadolinium (Gd) have been measured in thin film formulations on interdigitated gold (Au) electrodes for the applied voltage ([Formula: see text] range of [Formula: see text]. The conduction mechanism is found to be Ohmic within the bias of [Formula: see text] while the bulk limited Poole–Frenkel mechanism is responsible for the higher bias. The compounds show individual characteristics depending on the central metal ions, substituent chain lengths and their mesophases. Values of 67.55 [Formula: see text]cm[Formula: see text] and 42.31 [Formula: see text]cm[Formula: see text] have been obtained for room temperature in-plane Ohmic conductivity of as-deposited octyl lutetium (C[Formula: see text]LuPc[Formula: see text] and hexyl gadolinium (C[Formula: see text]GdPc[Formula: see text] films, respectively while C[Formula: see text]GdPc[Formula: see text] films exhibit nearly two orders of magnitude smaller conductivity. On annealing at 80[Formula: see text]C, Ohmic conductivities of C[Formula: see text]LuPc[Formula: see text] and C[Formula: see text]GdPc[Formula: see text] are found to have increased but the conductivity of C[Formula: see text]GdPc[Formula: see text] decreased by more than one order of magnitude to 1.5 [Formula: see text]cm[Formula: see text]. For physical interpretation of the charge transport behavior of these three molecules, their UV-vis optical absorption spectra in the solution and in as-deposited and annealed solid phases and atomic force microscopy study have been performed. It is believed that both orientation and positional reorganizations are responsible, depending upon the size of the central ion and side chain length.

C568: A new two-dimensional sp2-sp3 hybridized allotrope of carbon

Using first-principles calculations, we designed a new two-dimensional sp2−sp3 hybridized allotrope of carbon. This allotrope is made up of 5-6-8 carbon rings thus, known as C568. C568 is an indirect semiconductor with a band gap of 1.13 eV (HSE06) at Γ-M symmetric point in the Brillouin zone. The possibility of the existence of C568 is evident from its energetic, dynamical, mechanical, and thermal stabilities. C568 maintains its structural integrity up to 800 K, which we confirmed by employing ab-initio molecular dynamics (AIMD) simulations. C568 shows extraordinary room temperature in-plane electronic mobility of order ∼104 cm2V−1s−1, which is significantly higher than the black phosphorus (∼103 cm2V−1s−1) monolayer. Energetically, this sheet is more stable than the other sp2−sp3-hybridized carbon allotropes such as pentagraphene and tetrahexcarbon. Moreover, C568 can be stacked into three different configurations, which also exhibit interesting electronic as well as transport properties. These configurations are also dynamically stable and show in-plane mobilities of order ∼104 cm2V−1s−1.

Strong Pauli paramagnetic effect in the upper critical field of KCa2Fe4As4F2

Recently, 12442 system of Fe-based superconductors has attracted considerable attention owing to its unique double-FeAs-layer structure. A steep increase in the in-plane upper critical field with cooling has been observed near the superconducting transition temperature, $T_c$, in KCa$_2$Fe$_4$As$_4$F$_2$ single crystals. Herein, we report a high-field investigation on upper critical field of this material over a wide temperature range, and both out-of-plane ($H\|c$, $H_{c2}^{c}$) and in-plane ($H\|ab$, $H_{c2}^{ab}$) directions have been measured. A sublinear temperature-dependent behavior is observed for the out-of-plane $H_{c2}^{c}$, whereas strong convex curvature with cooling is observed for the in-plane $H_{c2}^{ab}$. Such behaviors could not be described by the conventional Werthamer--Helfand--Hohenberg (WHH) model. The data analysis based on the WHH model by considering the spin aspects reveals a large Maki parameter $\alpha=9$, indicating that the in-plane upper critical field is affected by a very strong Pauli paramagnetic effect.

The role of mid-gap phonon modes in thermal transport of transition metal dichalcogenides**Notice: This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish

We present a comprehensive theoretical study on thermal transport in monolayer transition metal dichalcogenides MX2 (M: Mo, W; X: S, Se) with various sample sizes. An unusually high anharmonic scattering strength is found in MoSe2 compared to the other three family members, which arises from its unique phonon band dispersion, specifically the mid-frequency phonon branches associated with the vibrations of Se atoms of MoSe2. The mid-frequency modes almost completely span the gap that exists between the high-frequency phonon branches and the acoustic ones, allowing the former to readily decay into the latter. The resultant high anharmonic scattering gives rise to a short mean free path which makes the room temperature in-plane thermal conductivity in MoSe2 even lower than WSe2 when the sample length is larger than 51.5 nm. With varying sample sizes, the ordering of thermal conductivity among the four materials changes as phonon transport transits from the ballistic to diffusive regime, driven by the competition between the phonon frequency spectrum range and the scattering strength. Our work provides a microscopic picture of phonon transport in TMDs and guidance to tailor their thermal conductivities for electronic and thermoelectric applications.

Uniform hole doping in HgBa2Ca2Cu3O8+δ studied by 63Cu NMR

We studied local magnetic properties of triple-CuÜ2-layer superconductors HgBa2Ca2Cu3O8+δ with rich 63Cu isotope (underdoped Tc = 124 K and optimally doped Tc = 134 K) by 63Cu NMR spin-echo techniques. The temperature dependences of the 63Cu nuclear spin-lattice relaxation rate 63(1/T1) and the spin Knight shift 63Kspin of the inner plane Cu(1) site were nearly the same as those of the outer plane Cu(2) site in the normal states. The pseudogap temperature T* defined as the maximum temperature of 63(1/T1T) was 190 K for the underdoped Tc = 124 sample and 143 K for the optimally doped Tc = 134 K sample. The NMR results indicate the uniform hole distribution in the three layers, which is consistent with a coalescence of three-derived Fermi surfaces predicted by a band theory. The room temperature in-plane depends on whether the number of CuO2 planes per unit cell is even or odd for the Hg-based multilayer cuprate superconductors.

Hierarchical Twinning Induced Texture Weakening in Lean Magnesium Alloys

Rolled and annealed Mg-1wt. %Zn-1wt. %Gd-0.6wt. %Zr (ZEK110) alloys were subjected to room temperature in-plane compression along the rolling direction, followed by isochronal annealing treatments for 1 h. Despite a starting orientation favoring c-axis extension, the as-deformed microstructure revealed a hierarchical network of twins with profuse quantities of second and third generation twinning appearing within primary tension and compression twins. Complex twin-twin and twin–particle interactions were accompanied by the activation of both basal and non-basal dislocation slip in the neighborhood. While the population density of twins nucleated was significantly high, twin growth was severely retarded due to the presence of secondary phases. In terms of the overall distribution of grain orientations, the as-deformed texture displayed a rather weak basal component with a large portion of the basal poles aligned towards the longitudinal direction with an angular spread of ± 30°. Recrystallization commenced within twins, at twin-twin intersections at lower annealing temperatures and occurred additionally near secondary phases at higher annealing temperatures, giving rise to diverse orientations of both basal and off-basal character. Subsequent growth led to favorable coarsening of the off-basal orientations resulting in an overall texture weakening. The findings provide critical insights with respect to engineering high-strength, high-ductility lean magnesium alloys, comprising hierarchical microstructures that are not only associated with favorable crystallographic textures but additionally display a multi-scale strengthening behavior.

Thermal transport in layer-by-layer assembled polycrystalline graphene films

New technologies are emerging which allow us to manipulate and assemble 2-dimensional (2D) building blocks, such as graphene, into synthetic van der Waals (vdW) solids. Assembly of such vdW solids has enabled novel electronic devices and could lead to control over anisotropic thermal properties through tuning of inter-layer coupling and phonon scattering. Here we report the systematic control of heat flow in graphene-based vdW solids assembled in a layer-by-layer (LBL) fashion. In-plane thermal measurements (between 100 K and 400 K) reveal substrate and grain boundary scattering limit thermal transport in vdW solids composed of one to four transferred layers of graphene grown by chemical vapor deposition (CVD). Such films have room temperature in-plane thermal conductivity of ~400 Wm−1 K−1. Cross-plane thermal conductance approaches 15 MWm−2 K−1 for graphene-based vdW solids composed of seven layers of graphene films grown by CVD, likely limited by rotational mismatch between layers and trapped particulates remnant from graphene transfer processes. Our results provide fundamental insight into the in-plane and cross-plane heat carrying properties of substrate-supported synthetic vdW solids, with important implications for emerging devices made from artificially stacked 2D materials.

Room temperature in-plane ferroelectricity in van der Waals In2Se3.

Van der Waals (vdW) assembly of layered materials is a promising paradigm for creating electronic and optoelectronic devices with novel properties. Ferroelectricity in vdW layered materials could enable nonvolatile memory and low-power electronic and optoelectronic switches, but to date, few vdW ferroelectrics have been reported, and few in-plane vdW ferroelectrics are known. We report the discovery of in-plane ferroelectricity in a widely investigated vdW layered material, β'-In2Se3. The in-plane ferroelectricity is strongly tied to the formation of one-dimensional superstructures aligning along one of the threefold rotational symmetric directions of the hexagonal lattice in the c plane. Surprisingly, the superstructures and ferroelectricity are stable to 200°C in both bulk and thin exfoliated layers of In2Se3. Because of the in-plane nature of ferroelectricity, the domains exhibit a strong linear dichroism, enabling novel polarization-dependent optical properties.

Tetrahexcarbon: A two-dimensional allotrope of carbon

A two-dimensional structurally stable carbon allotrope is predicted using first-principles calculations. This unique network is composed of tetra and hexa-rings of carbon atoms known as Tetrahexcarbon. Tetrahexcarbon has a quasiparticle (QP) direct band gap of 3.70 eV at Γ, which is closer to the ZnS, a well-known direct bandgap semiconductor. Interestingly, it is dynamically stable and can withstand temperature up to 1000 K, which is confirmed by performing phonon and ab initio molecular dynamics (AIMD) simulations. The mobilities of both electrons and holes in this material are found to be anisotropic. It exhibits extraordinary room temperature in-plane electron mobility of order ∼104cm2V−1s−1, which is an order of magnitude higher than the black phosphorus monolayer (∼103cm2V−1s−1) and two orders of magnitude higher than MoS2 (∼200cm2V−1s−1) monolayer. The optical response of Tetrahexcarbon obtained by applying Bethe-Salpeter equation (BSE) to include excitonic effects on top of the partially self-consistent GW0 calculation. The absorption onsets strongly depend on the light polarization directions indicating Tetrahexcarbon an anisotropic material.

Competitive twinning behavior in magnesium and its impact on recrystallization and texture formation

Rolled pure Mg and Mg-1wt% Gd alloy were subjected to room temperature in-plane compression along the rolling direction, followed by isochronal annealing treatments for 1h. The results of deformation texture and microstructure showed substantial differences due to rare earth alloying. In spite of imposed c-axis extension during deformation, the Mg-1Gd alloy retained the initial texture with the majority of basal poles concentrated near the longitudinal direction of the used channel-die tool. Electron back scatter diffraction analysis of the deformation microstructure revealed a predominance of {101̅1} compression and {101̅1}-{101̅2} double twins relative to coexisting {101̅2} tension twins. This behavior was significantly contrasting in comparison with that of pure Mg, wherein first and second generation {101̅2} tension twins were observed in profuse quantities. Continuous dynamic recrystallization took place inside compression and double twins by means of slip assisted subgrain rotation about the [0001] axis giving rise to a sharp prismatic fiber of recrystallized orientations. This fiber was transformed into a randomized texture pattern during subsequent static recrystallization and grain growth due to a different discontinuous recrystallization mechanism. This resulted in a significant annealing texture weakening and an increase of the overall Schmid factor for basal slip.