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Abstract Aurivillius single-phase Bi 2.5 Nd 0.5 Nb 1.5 Fe 0.5 O 9 (BNNF) ceramics was synthesized via solid state mixed oxide sintering method. Electrical properties of the samples were intensely studied in a wide range of temperature (25 °C–650 °C). Dielectric behaviors were investigated by dielectric and impedance spectroscopies in the range (40 Hz−10 MHz) of frequency. Single dielectric relaxation was observed due to the grains contribution. The phase transition temperature (T C) was noticed at ∼270 °C. Kinetic analysis of dielectric data was used to understand the possible relaxation-conduction behaviors in the ceramics. Above ∼250 °C, relaxation and conduction of the ceramics was assigned to the motion of ionized oxygen vacancies. The Aurivillius ceramics has promising industrial applications in dielectric capacitors and piezoelectric transducers due to low leakage below ∼200 °C. The results could be valuable for designing and/or modifying properties of BNNF related materials. Highlights • Aurivillius Bi 2.5 Nd 0.5 Nb 1.5 Fe 0.5 O 9 ceramics was synthesized for the first time. • A ferroelectric transition was observed at ∼270 °C. • Single dielectric relaxation was observed due to grains contribution. • Above ∼250 °C conduction and relaxation was due to ionized oxygen vacancies. [ABSTRACT FROM AUTHOR]

Structural, electronic, elastic and magnetic properties of CaCu 3 Mn 4-x Ir x O 12 (x = 0, 2 and 4) along with the optical properties of CaCu 3 Mn 4 O 12 perovskites have been carried out in the framework of density functional theory (DFT). The investigation of structural optimization reveals that CaCu 3 Mn 2 Ir 2 O 12 is stable in Pn-3 space group and CaCu 3 Mn 4 O 12 and CaCu 3 Ir 4 O 12 perovskites are stable in Im-3 space group. The cohesive energy and enthalpy of formation reveal the stability of these compound and shows that CaCu 3 Mn 2 Ir 2 O 12 is more stable than the rest compounds. Substitution of Ir by Mn not only transforms these compounds from semiconductor to metallic nature but also transform the host compound from ferrimagnetic to anti-ferromagnetic via spin glass state. The DFT electronic behavior is also supported by the electrical resistivity. Elastic properties demonstrate the mechanical stability, anisotropic and ductile nature of these compounds. The optical properties indicate that CaCu 3 Mn 4 O 12 is optically active for infrared electromagnetic radiations and could be used in optical devises. The ferrimagnetic ductile nature of CaCu 3 Mn 4 O 12 , spin glass and anti-ferromagnetic nature of CaCu 3 Mn 2 Ir 2 O 12 and CaCu 3 Ir 4 O 12 makes these perovskites suitable candidates for spintronic and magnetic cloaking applications. [Display omitted] • Structure symmetry is evaluated from Im-3 to Pn-3 via Ir substitution. • Substitution of Ir transform these compounds from semiconductor to metallic nature. • The ferrimagnetic is transform to anti-ferromagnetic via Spin glass state. • CaCu 3 Mn 4 O 12 is optically active in infrared region of electromagnetic spectrum. [ABSTRACT FROM AUTHOR]

In the present density functional studies, structural, mechanical and magneto-electronic properties of CaTaO 3, SrTaO 3 and BaTaO 3 perovskites have been investigated. The calculated structural parameters by DFT and analytical methods are found consistent with the experiments. The analytically calculated tolerance factors of these compounds as well as their mechanical properties show that they are stable in the cubic phase. Furthermore elastic properties show that these materials are ductile in nature and confirm that BaTaO 3 is harder than the rest compounds. The calculated spin dependent magneto-electronic properties reveal the paramagnetic metallic nature of these compounds. The electrical conductivity curve demonstrates significant conductivity above room temperature. On the basis of the presented properties it is expected that these compounds could be efficient electrode materials and need experimental investigations. [ABSTRACT FROM AUTHOR]

In this article anode materials of silicon carbide and III-nitride nanosheets are investigated for magnesium ion batteries (MIBs) as possible alternative of lithium and sodium ion batteries. The calculated density functional theory results reveal higher values of internal energy change and cell voltage for MIBs with silicon carbide, boron nitride, aluminum nitride and gallium nitride anode material than the previously reported carbon nanomaterials. The nanosheet shows stronger binding capacity for Mg ion both in monolayer and bulk phase. The adsorption energies and cell voltage decreases as the concentration of Mg ions over nanosheet increased. The lower values (0.05–0.37 eV) of diffusion barriers prove the faster mobility of Mg ion in 2D nanosheet. The boron nitride and silicon carbide exhibit a high storage capacity of 1619.90 mA h/g and 1002.64 mA h/g respectively. Therefore, silicon carbide and III-nitride nanosheets based anode MIBs could be a promising alternative of lithium ion batteries and needs further studies. Image 1 • SiC and III-nitrides nanosheets investigated as anodes in MIBs using DFT study. • Mg2+ shows stronger adsorption energies which results higher cell voltage. • BN and SiC shows high specific capacity of 1619.90 mA h/g and 1002.64 mA h/g. • III-Nitrides and SiC nanosheets have low migration-barrier 0.05–0.37 eV. [ABSTRACT FROM AUTHOR]

The structural, magnetic and elastic properties of orthorhombic phase of RAu 2 compounds (R = La, Ce, Pr and Eu) are reported theoretically for the first time using full potential linearized augmented plane waves method within the density functional theory. The structural properties are investigated by treating the exchange and correlation energies with the generalized gradient approximation, PBEsol. Our computed lattice constants are found consistent with the reported experimental results. Our data reveal that they are stable in orthorhombic CeCu 2 type structure. Their mechanical properties such as Young, Shear and bulk moduli, Poisson and anisotropic ratio, Cauchy pressure and B o /G ratio are explored using the PBEsol to evaluate the importance of these compounds in various types of engineering applications. One of the striking features of their mechanical properties is their ductile nature. Magnetically all these intermetallics are antiferromagnetic. [ABSTRACT FROM AUTHOR]

Structural, electronic and magnetic properties of the perovskites SrFe 1-x Co x O 3 (x = 0, 0.25, 0.50, 0.75 and 1) are investigated using generalized gradient approximation (GGA) and GGA with Hubbard potential within the frame work of spin-polarized density functional theory (DFT). The calculated structural parameters and geometries are consistent with the experimental results and observed decrease in the lattice constants with increase in Co concentration. The bonding nature is visualized through electron charge densities and confirms that the bond between Sr−Fe/Co is ionic, Fe/Co−O is covalent and Co−Fe is metallic. Band profiles comparison and electrical properties reveal that these compounds are metallic. It is observed that the magnetic interaction is anti-ferromagnetic at Fe rich side while ferromagnetic for Co substituted compounds. The transition of anti-ferromagnetism to ferromagnetism is explained through exchange interactions. [ABSTRACT FROM AUTHOR]

Aluminum doped Cu–Ni based spinel nano-ferrites Cu 0.7 Ni 0.3 Fe 2-x Al x O 4 are synthesized via sol-gel route and characterized by XRD, FTIR, impedance analyzer, EDAX and SEM. Phase analysis reveals a cubic spinel structure having a single phase. SEM images confirms the uniform formation of materials and elemental stoichiometry is confirmed from EDAX spectra. The size of crystals is within the range of 28.38–30.04 nm. The lattice constant decreases from 8.614 to 8.604 Å with the increase of Al3+ concentration. The metal-oxygen oscillations at octahedral and tetrahedral sites are confirmed by FTIR. Dielectric constant, tangent loss and quality factor are investigated using impedance analyzer within frequency range 1 MHz–3 GHz. Dielectric constant is significantly affected with Al3+ substitution and attained 16.1 value at 2.3 GHz for Cu 0.7 Ni 0.3 Fe 1.7 Al 0.3 O 4. Furthermore, Cu 0.7 Ni 0.3 Fe 1.7 Al 0.3 O 4 showed maximum dielectric loss of 0.4 at 2.5 GHz. The quality factor is enhanced up to 1500 with substitution of Al3+ at concentration of x ═ 0.3. Outstanding dielectric properties of nano-particles suggest that they are good candidates for high-frequency devices and super-capacitors. [Display omitted] • Cu0.7Ni0.3Fe2-xAlxO4 spinel ferrites were synthesized by solgel route. • Crystalline size was in the range of 28.38–30.04 nm. • Aluminum incorporation increased the dielectric constant value (16.1). • The material can be used for microwave absorbing application. [ABSTRACT FROM AUTHOR]

Structural, electronic, optical and magnetic properties of titanium based perovskites La 2 MTiO 6 (M = Co, Ni, Cu and Zn) are investigated in monoclinic phase with space group (P2 1 /n) in the domain of density functional theory (DFT). The generalized gradient approximation plus Hubbard potential (GGA + U) is utilized to study these high correlated electrons systems. Structural parameters are found in closed agreement with experiments. Cohesive energy reveals that La 2 CoTiO 6 is more stable among these compounds. The electronic properties show the semiconductor behavior of these compounds with band gap varies from 1.02 to 2.3 eV. Optical properties demonstrate that all these compounds are potential candidates for optoelectronic devices. The electrical resistivity which increases in a sequence from Co to Zn also confirms the semiconductor nature of these compounds. The magnetic susceptibility curves show that La 2 CoTiO 6 , La 2 NiTiO 6 and La 2 CuTiO 6 are antiferromagnetic whereas La 2 ZnTiO 6 is a paramagnetic material. Based on the semiconductor antiferromagnetic nature of La 2 CoTiO 6 , La 2 NiTiO 6 and La 2 CuTiO 6 it is expected that these compounds could be used as pinning layers in spin valves and storage devices. • La 2 MTiO 6 (M = Co, Ni, Cu and Zn) perovskites are semiconductors with band gaps ranges from 1.2 to 2.3 eV. • These compounds are optically active in the broad range electromagnetic spectrum. • Electrical resistivity increases in a sequence from Co to Zn and confirms the semiconductor nature of these compounds. • Perovskites La 2 CoTiO 6 , La 2 NiTiO 6 and La 2 CuTiO 6 are antiferromagnetic whereas La 2 ZnTiO 6 is a paramagnetic material. [ABSTRACT FROM AUTHOR]

AMn 3 V 4 O 12 (A = Ca, Ce and Sm) quaternary perovskites are studied in the domain of density functional theory using various potentials. Generalized gradient approximation along with Hubbard U and hybrid density functional schemes are found effective tools for the treatment of these compounds. Changing of A-site cation, affects the physical properties due to the valence distributions Ca+2Mn+2 3 V+4 4 O 12, Ce+3Mn+2 3 V+3.75 4 O 12 and Sm+3Mn+2 3 V+3.75 4 O 12 respectively. Cohesive energy and enthalpy show that these compounds are thermodynamically stable. Electronic and electrical properties reveal the semi-metallic nature of these compounds. It is observed that in these compounds Aʹ-site (Mn) 3d electrons are localized and responsible for the magnetic properties whereas B-site (V) 3d electrons are delocalized, contributed in the electronic behavior. The elastic properties also confirm the stability and demonstrate that these compounds are ductile in nature. DFT as well as post−DFT treatments verify the anti-ferromagnetic nature of these compounds with the dominant Mn+2―O−2―Mn+2 super exchange interactions. • Cohesive energy and enthalpy show that these perovskites are thermodynamically stable. • Elastic properties confirm the stability and demonstrate that these compounds are ductile. • Electronic band profiles and electrical properties reveal the semi-metallic nature of the compounds. • These compounds are anti-ferromagnetic with the dominant Mn+2―O−2―Mn+2 super exchange interactions. [ABSTRACT FROM AUTHOR]

Manganese oxide (MnO x) is a low cost and environment-friendly electrode material for supercapacitors. Although most efforts have been devoted to increase the surface area of this material, the role of surface defects in different MnO x polymorphs towards improvement of its capacitance remains to be thoroughly investigated. In this paper, the results from electrodeposition of mesoporous MnO x thin film electrodes and the effect of rapid thermal annealing (RTA) on their electrochemical storage behavior are presented and discussed. X-ray photoelectron spectroscopy (XPS) analyses showed an increase of the Mn2+/Mn3+ ratio as well as hydroxyl group defects on the surface of the annealed electrodes. The as-deposited MnO x did not manifest any capacitance behavior in 1.0 M Na 2 SO 4 electrolyte solution. However, after RTA treatment, the specific capacitance was tremendously enhanced. An areal capacitance as high as 110 mF cm−2 at 5 mV s−1 was recorded in 1.0 M Na 2 SO 4 electrolyte with a capacitance retention of 74% after 5000 charge-discharge cycles. Furthermore, the RTA treatment of electrodes significantly decreased the charge transfer resistance value from 0.678 × 106 Ω for the pristine MnO x electrode to 39.13 Ω for the treated one. Based on structural and surface chemistry evolution of the MnO 2 films after annealing, the electrochemical storage behavior of annealed MnO x is discussed. Image 1 • Electrodeposited mesoporous MnO 2 films were treated for rapid thermal annealing. • XPS analysis confirmed Mn2+/Mn3+ increase besides hydroxyl groups attachment. • RTA treatment decreased the charge transfer resistance from 0.678 MΩ to 39.13 Ω. • EIS indicated excellent pseudocapacitive behavior due to large electroactive area. • High areal capacitance and cyclic stability up to 5000 cycles were achieved. [ABSTRACT FROM AUTHOR]