A combined experimental and theoretical study demonstrates the effect of small Bi substitution at Na-site on the crystal structure, ionic conductivity and Na+ diffusion channels of Bi-substituted NASICON material, Na1-x BixTi2-x (PO4)3 for x = 0.0, 0.03 and 0.05. Rietveld refinement of the x-ray diffraction patterns reveals 2 that these materials exhibit rhombohedral symmetry in the R 3 c space group. Impedance analysis revealed that Bi0.03-doped NTP exhibited a bulk ionic conductivity of 1.02 & times; 10-6 S/cm at room temperature, which is one order of magnitude higher than the ionic conductivity 1.34 & times; 10-7S/cm of the pristine NTP. The Arrhenius behaviour of the temperature-dependent study of the bulk contribution to the ionic conductivity yielded the activation energy (Ea(b)) for Bi0.03-NTP is 0.33(5) eV, which is lower than 0.47(2) eV, obtained for pristine NTP. Furthermore, the migration of Na+ within the skeletal framework of Bi-substituted NaTi2(PO4)3 was investigated using density functional theory (DFT) calculations. The calculated partial density of states reveals a weak covalent interaction between bismuth and oxygen ions in Bi-doped NTP. This interaction increases the covalency of the Ti-O bond, thereby widening the bottleneck area of the Na + diffusion channel from 5.25 to 5.36 & Aring;2. Furthermore, the estimated migration energy for Na+ hopping between two crystallographic sites is reduced from 0.79 eV in pure NTP to 0.69 eV for the Bi-doped NTP. These results suggest that Bi-substitution at Na-site in NASICON may be an alternative way to improve their ionic conductivity.

Rare-earth-doped metal oxides hold great promise as high-performance supercapacitor electrodes. In this work, nanostructured Cu1-xEuxO (x = 0.0, 0.01, 0.02, and 0.03) electrode materials were synthesized and systematically investigated through structural, electronic, electrochemical, and DFT analyses. Structural characterization confirms that all samples crystallize in a monoclinic phase and reveals slight lattice distortions and Cu-O bond stretching upon Eu3+ doping. The results demonstrate an increased concentration of oxygen vacancy defects in Eu3+-doped CuO, which likely enhances electrochemical performance by improving conductivity and increasing the density of electrochemically active sites. Compared with pristine CuO and other Cu1-xEuxO compositions, the Cu0.98Eu0.02O electrode exhibits the highest specific capacitance of 1050 F/g at 1 A/g, along with excellent cyclic stability (similar to 93.7%) after 10,000 charge-discharge cycles. Kinetic analysis confirms a diffusion-controlled energy storage mechanism in the Eu3+-doped CuO electrode. Furthermore, the fabricated solid-state symmetric supercapacitor based on Cu0.98Eu0.02O nanoparticles delivers a high energy density of 47.23 Wh/kg at a power density of 674.87 W/kg. DFT calculations of the density of states reveal that the enhanced specific capacitance of Eu3+-doped CuO originates from the localized Eu3+ 4f(6) states near the Fermi level, which contribute to increased quantum capacitance.

We present studies of the structural optimization of the full Heusler alloys Co2XZ (X = Ti, Hf, and Z = Si, Ge, Al) and their electronic, magnetic, mechanical, and thermoelectric properties using first-principle calculations. The structure of these alloys was found to be stable in the cubic phase with Fm 3 m space group in their ferromagnetic phase. The total magnetic moment of these alloys satisfies the Slater–Pauling rule and predicts their ferromagnetic half-metallic character. The elastic constants suggest that they are mechanically stable and ductile. The electronic density of states and band structure calculations reveal that these alloys exhibit half-metallic behavior with high spin polarization in their stable ferromagnetic phase. Investigation of thermoelectric properties reveals that Co2HfAl exhibits a relatively high Seebeck coefficient (S) and figure of merit (ZT) (S = −110 µV/K and ZT = 0.4 at 800 K) as compared to the other studied alloys. The results for these alloys predict their potential application as spintronic and thermoelectric materials.

Wearable supercapacitors (SCs), commonly known as smart SCs, have garnered much attention for wearable and Internet of Things (IoT) devices, including smartwatches, sensors, and health monitoring patches. In this direction, the developments of low-cost, flexible, and lightweight electrodes for SCs are highly demanded. Here, an efficient wearable supercapacitor based on copper oxide nanostructures on carbon cloth (CuO Ns/CC) was fabricated by a cost-effective, binder-free, additive-free and simple method of electrodepostion. The CuO Ns/CC electrode exhibits a high specific capacity of 326.6 C/g at 2 A/g and excellent cyclic stability (capacitance retention 97.8

The mechanochemical synthesis route has become popular for the solvent-free synthesis of a wide range of hybrid halide perovskites. This work demonstrates that mechanochemically synthesized CH3NH3PbBr3 is thermally more stable compared to chemically processed material and free from deep-level defects. Temperature-dependent structural study on mechanochemically synthesized material reveals that it exhibits a cubic phase at room temperature with a phase transition from cubic to tetragonal phase at 230 K. Below 150 K, it transforms into an orthorhombic phase, which belongs to an incommensurately modulated crystal structure (Imma(s00)00 gamma). Unlike the early reports, the orthorhombic Pnma structure is absent, and the modulated phase is extended over a wide range of temperatures from 145 K to 100 K. Temperature-dependent photoluminescence study shows that the emission spectrum comprises both the contribution from free and bound excitons. The blueshift of the bandgap with increasing lattice temperature can be explained by the large volume expansion coefficient (of the order 10-4), which dominates over the contribution due to electron-phonon coupling. The linewidth broadening of the emission spectrum is mainly due to the interaction of the longitudinal optical phonon with the free electron. The photo-generated exciton exhibits high activation energy (similar to 100 meV) at room temperature, demonstrating its potential for light-emitting device applications.

We present the mechanical and electronic properties of the transition metal nitrides (TMNs) VN, TiN, and NbN using density functional theory calculations. These nitrides are thermodynamically stable in the cubic phase with Fm3 m space group symmetry. The elastic constants calculated by applying various volume-conserving strains reveal that NbN and VN are ductile, whereas TiN is brittle and exhibits good mechanical stability. The electronic band structures, density of states, and partial density of states are calculated to investigate the electronic behaviour of these TMNs. The electronic band structures indicate the metallic behaviour of these TMNs. The partial density of states reveals hybridization between d-orbitals of transition metal and p-orbitals of nitrogen. Further, the quantum capacitance (CQ) values are calculated from the total density of states at various operating voltages. We find that VN exhibits the maximum CQ = 2588 F/g at the Fermi level and reaches 5135 F/g at + 0.6 V operating voltage.

We present the influence of electrolyte solutions on the electrochemical performance of NaTi2(PO4)3, as an electrode material for supercapacitor applications. The NaTi2(PO4)3 ceramic material was successfully synthesised in the rhombohedral phase with R3c space group, as confirmed by the Rietveld refinement of the x-ray diffraction data. Electrochemical impedance spectroscopy studies revealed that charge transfer resistance in KOH electrolyte is significantly lower than in NaOH, indicating higher ionic conduction in KOH. The specific discharge capacities of the NaTi2(PO4)3 electrode material in KOH and NaOH solutions were found to be 75.46 mAh/g and 6.3 mAh/g, respectively. Moreover, the energy density reached 54.16 Wh/kg at a power density of 1612 W/kg in KOH electrolyte, which is significantly higher than the 3.73 Wh/kg at 1532 W/kg observed in NaOH electrolyte. The electrode also exhibited excellent cycling behaviour, with less than 2 % capacitance loss after 10,000 cycles in KOH electrolyte, compared to 15% in NaOH electrolyte. Further, the mechanisms of electrochemical behaviour and associated chemical reactions in KOH and NaOH electrolytes were investigated using density functional theory (DFT) calculations. These findings highlight NaTi2(PO4)3 as a promising electrode material for KOH electrolyte-based supercapacitors.

The natrium superionic conductors (NASICON) family of materials is being widely examined as a solid-state electrolyte for sodium-ion batteries (SIBs). We present a combined experimental and theoretical study of the crystal structure and ionic conductivity of a NASICON NaTi2(PO4)3. Rietveld refinement of the x-ray diffraction pattern reveals that the prepared single phase NaTi2(PO4)3 exhibits rhombohedral symmetry in the R3¯c space group. The elemental analysis by energy dispersive spectroscopy (EDS) confirms the desired composition of NaTi2(PO4)3. The ionic conductivity evaluated from the electrochemical impedance spectroscopy measurements as a function of temperature shows Arrhenius-type relaxation behaviour with activation energy ~0.47(2) eV. A sizable ionic conductivity (~1.16×10-3S/cm at 600K) has been observed for NaTi2(PO4)3. Further, the migration of Na+ via a sigmoidal path in the skeleton of NaTi2(PO4)3 has been investigated by the density functional theory (DFT). The estimated migration energy for the hopping of Na+ between two crystallographic sites is found to be 0.79eV. The calculated conductivity (3.03×10-7S/cm) resulting from the interstitial diffusivity of the Na-ion is consistent with the measured ionic conductivity at room temperature (~1.34×10-7S/cm). While the wide calculated electronic band gap (2.52eV) suggests poor electronic conductivity of NaTi2(PO4)3, it could be beneficial for solid electrolyte applications.

In the present work, we study the geometric, electronic, magnetic and mechanical properties of Co-based full Heusler alloys Co 2 TaZ (where Z = Si and Sn). Structural optimization and physical properties have been investigated using density functional theory (DFT) calculations. While calculating electronic and magnetic properties, the GGA+ U scheme, where U is the Hubbard term, predicts more efficient results than the generalized gradient approximation (GGA). The calculated electronic band structure and density of states (DOS) with spin magnetic moment reveal the half-metallic character of both alloys. The total computed magnetic moment amounts to a nearly integral value of 3 μ B for Co 2 TaSi and Co 2 TaSn. It has been found that these alloys obey the Slater–Pauling rule. The calculated values of elastic constants indicate that these alloys are mechanically stable, difficult to compress and ductile. The high spin polarization at the Fermi level in these alloys makes them useful for spintronic applications.

Co3-xAgxO4 (x = 0 similar to -0.4) nanocomposite with a spherical shape and porous surface has been synthesized using a simple, fast and scalable combustion method. The highly stable Ag-doped Co3O4 nanocomposite particles were found to be 20--50 nm in size with high surface area, crystallinity, and porosity. The specific capacitance value of the Co2.7Ag0.3O4 (CA(3)) electrode was observed to be higher than other electrodes. Doping of Ag provides a large Ag/Co3O4 interface which enhanced the electrical conductivity of the electrode by moulding ohmic contact. This contributes to a stable and straight passage for rapid charge transfer. The calculated specific capacitance value of CA(3) nanocomposite was 648 F g(--1) at a current density of 0.25A g(--1) which was 6-fold greater than the undoped Co3O4 and 2--4-fold greater than Ag-doped Co3O4 nanocomposites prepared at other concentrations. The electrodes exhibited excellent cyclic stability with capacitance retention of 93% after 10,000 cycles having an energy density of 88.23 Wh kg(--1) at 1.75 kW kg(--1) power density indicating a promising material for supercapacitor application. Fabricated symmetric solid-state flexible device of Ag-doped Co3O4 also demonstrated reliable charge storage performance with a maximum energy density. The theoretical study also revealed that Ag doping into Co3O4 introduces additional localized states around the fermi level, between the highest occupied states and lowest unoccupied states. The presence of higher localized states near the Fermi level and smaller bandgap than Co3O4 enhanced the specific capacitance of the system, providing support to the experimental observation on improvement in energy charge storage.

The magnetic properties and exchange bias of the heterostructures of a ferroelectric-antiferromagnetic room-temperature multiferroic BiFeO3 (BFO) and a ferromagnetic La2/3Sr1/3MnO3 (LSMO), grown on SrTiO3 (STO) substrate using pulsed laser (PLD) deposition technique, as a function of temperature are explored. The irreversible behaviour of temperature-dependent field cooled (FC) and zero-field cooled (ZFC) magnetization curves, with blocking temperature (T-B) similar to 250 K, and exponential decay of coercive field (H-c) below T-B, reveal a spin-glass like state in BFO/LSMO heterostructure. The exchange bias is observed in asgrown as well as electrically poled BFO in BFO/LSMO which diminishes above the blocking temperature. A considerable impact of electrical poling on the magnetic properties and exchange bias is noticed in the BFO/LSMO heterostructure. In the proposed model, the coupled ferroelectric/antiferromagnetic orders in BFO along with the inflection of exchange interactions between Fe3+ and Mn3+/(4+) in the vicinity of the interface due to the movement of Fe3+ in BFO relative to Mn3+/(4+) in LSMO during the ferroelectric polarization switching is the key factor that strongly influences the magnetic properties and exchange bias BFO/LSMO heterostructure. (C) 2022 Elsevier B.V. All rights reserved.

New heteroleptic Ni(ii)dppe dithiolate synthesized and used as a single source precursor for nickel sulfides utilized as electrocatalyst for OER.

BiFeO3 (BFO) thin films with different thicknesses were deposited on La0.67Sr0.33MnO3 (LSMO) buffered SrTiO3 (001) substrate using a pulsed laser deposition technique. The variation in the out-of-plane lattice parameter and magnetic properties of BFO/LSMO with various thicknesses of BFO are explored. The lattice parameter of BFO decreases with the increasing thickness of BFO and approaches to a value corresponding to bulk BFO. The remanent magnetization (M-r) and magnetic coercive field (H-c) of BFO/LSMO heterostructures depend on the thickness of the top layer BFO. The maximum values of M-r and H-C in BFO/LSMO are observed for BFO with thickness (t(BFO)) equal to ~25 nm. For t(BFO) > 25 nm, both M-r and H-c of BFO/LSMO decrease with increasing thickness of the BFO layer. Further, a wasp-waisted shape in the M-H loop of BFO/LSMO perceptible at a high temperature (100 K) may be originated from a new magnetic phase in the BFO layer at the interface due to Fe3+ and Mn3+/4+ magnetic interactions between the two layers. The exponential decay of the H-C(T) with increasing temperature suggests the multiple competing interactions, such as Fe3+-O-Fe3+ and Fe3+-O-Mn3+/4+ and Mn3+/4+-O-Mn3+/4+ leading to a spin-glass state in the interfacial region. The variations in the magnetic properties of BFO/LSMO with the thickness of BFO may be associated with the single domain to multi-domain transition and/or linked to the effect of the epitaxial strain, and Fe3+ and Mn3+/4+ magnetic interactions in the vicinity of the interface.

A trinuclear heterobimetallic complex with general formula [Cu(PPh3)S2MoS2Cu(PPh3)2]·CHCl3 (SSP) has been synthesized, and its characterization executed using FTIR, NMR, electronic absorption spectroscopies, and single‐crystal X‐ray technique. The complex is solvothermally decomposed in octadecylamine (ODA) to yield ternary copper molybdenum sulfide nanoparticles and successfully grafted onto 2D materials, namely, reduced graphene oxide (rGO) or polyaniline (PANI), and these composites are utilized for oxygen evolution half‐cell reaction (OER). The copper molybdenum sulfide nanoparticles as well as their composites with rGO and PANI and rGO + PANI were characterized using powder X‐ray diffraction, SEM, and EDX analyses. Electrochemical measurements suggested that the modified electrodes have notable electrocatalytic activity toward OER with onset overpotential 400 mV for CMS + PANI and 395 mV for CMS + rGO + PANI. This is the first study on the use of copper molybdenum sulfide nanoparticles composites with rGO and PANI as electrocatalysts for OER displaying substantial synergistic activity.

In the present work, we explored the interplay between the lattice and magnetic degrees of freedom in a rare-earth nickelate EuNiO3, by carrying out temperature-dependent structural analysis in conjunction with distortion mode analysis. The temperature-dependent powder synchrotron x-ray diffraction (SXRD) studies revealed the presence of an orthorhombic Pbnm phase (tilt system a-0 a-0 c+0 ), with an elementary perovskite (pseudomonoclinic) cell, over the analyzed temperature range, i.e., 100-623 K. Further, we observed two distinct anomalies in the temperature-dependent evolution of pseudomonoclinic cell parameters (cp/ap, gamma, Vmono) around 463 K and 200 K corresponding to respective isosymmetric metal-insulator transition temperature (TM -I), and Neel temperature (TN) linked with a volume gain at low temperatures dictating a magnetoelastic coupling in the system. We show the existence of two distinct pseudomonoclinic phases, viz., Monometal (T > TM -I) and Monoinsulator (T < TM -I), where the latter is more distorted than the former. The transition from Monometal to Monoinsulator at TM -I is reminiscent of a phase transition from orthorhombic (metallic) to monoclinic (insulating) phase, observed in other members of the rare-earth family. In addition, TM -I and TN are clearly evident by the nonanalytical behavior of the condensed soft phonon modes amplitude corresponding to the zone boundary of the cubic Brillouin zone, viz., X5+ (q = 0, 1/2, 0) and R+5 (q = 1/2, 1/2, 1/2) as a function of temperature.

A sizable exchange bias (HEB-30Oe at 10 K) in the magnetic hysteresis of BiFeO3/La2/3Sr1/3MnO3 heterostructure is observed under the cooling field (+/- 3 kOe) applied perpendicular to the surface of the films. The exchange bias field (HEB) decreases with increasing temperature and becomes zero above 200 K. The temperature-dependent field cooled (FC) and zero-field cooled (ZFC) magnetization curves show irreversible behaviour, with a blocking temperature (TB) -225 K. The coercive field of the hysteresis loop, below the blocking temperature, decays exponentially with increasing temperature. These magnetic characteristics of BiFeO3/La2/3Sr1/3MnO3 heterostructure point towards a possibility of a spin-glass-like state due to the magnetic exchange interactions between the magnetic ions of both the layers in the vicinity of the interface, leading to complex magnetic structure. The sizable exchange bias observed below the blocking temperature is most likely originated from the exchange coupling between the magnetic ions at the interface.

This work contains an extensive study on temperature dependent complex dielectric behavior over 4 Hz <_ f <_ 8 MHz of a promising hybrid perovskite, propylammonium lead bromide. The structural, as well as morphological property of this sol-gel derived sample have been analyzed with the help of XRD and SEM respectively. The obtained energy band gap and thermal stability study ensure the capability of this material in device fabrication. Possessing a wide band gap, this perovskite fascinatingly serves as a UV photodetector. The individual impact of grain and grain boundary over the entire resistance has been resolved by Maxwell - Wagner Cole-Cole model. This material holds an amazing property; giant dielectric constant near room temperature at low frequency limit which escalates rapidly in the influence of thermal effect. Modified cole - cole plot assures that both space and free charge conductivities ascend with temperature. The asymmetrical nature of the imaginary part of electric modulus is analyzed by Kohlrausch - Williams - Watts which confirms its non - Debye nature diminishes with rising temperature. The thermally triggered AC conductivity follows Jonscher's power law and is emphasized with the jump relaxation model. The bulk conductivity of the sample depends on temperature and is elucidated with variable range hopping of localized charge carriers. Activation energy plays a key role in the ionic conduction mechanism within the sample, described elaborately. The overall substantial studies on its application as UV detector and different dielectric properties of this sample construct the basis of appreciable acceptability of the sample in energy harvesting. (c) 2021 Elsevier B.V. All rights reserved.

Efficient oxygen evolution reaction catalyst can be prepared via controlled decomposition method, and there is still minimal mechanistic understanding of such method. Here, we introduce a 3-Bromo-salophen ligated nickel(II) and copper(II) complexes as a precursor to obtain a Ni and Cu-based oxygen evolution reaction electrocatalyst via the controlled decomposed method. In our case, the unique O,N chelation mode of the 3-Bromo-salophen ligand (bis[2-bromosalicylydene]-1,2-iminophenylenediamine) was used to synthesize M(II) complexes. By regulating the decomposition conditions, we successfully obtained varied structures. The designing of a nonprecious, highly efficient and long-lasting oxygen evolution reaction electrocatalyst for electrochemical water splitting is a current emergency for reducing energy demand in the future. In this study, we found cost-effective decomposed products of NiO and CuO which are prepared by a simple one-step chemical precipitate method at high temperature (500 degrees C). The chemical composition, structure and morphology of the decomposed products NiO and CuO were confirmed by PXRD, FTIR and SEM spectroscopy. The decomposed products were loaded onto a glassy carbon electrode by a drop-casting method. For the oxygen evolution reaction, the complexes as well as their decomposed products, NiO and CuO achieve an ultralow over-potential exhibit onset lower potential 1.5 V in 0.1 M KOH solution. (c) 2021 Published by Elsevier B.V.