Tetragonal Crystal Symmetry Research Articles

Crystal Structure, Magnetic, and Dielectric Properties of (x)CoFe2O4–(1−x)Ba0.8Sr0.2TiO3 Multiferroics

The composites (x)CoFe2O4–(1−x)Ba0.8Sr0.2TiO3 are prepared by solid‐state reaction method using microwave double‐step sintering. Ba0.8Sr0.2TiO3 crystallizes to tetragonal crystal symmetry with P4mm space group and CoFe2O4 crystallizes to cubic crystal symmetry with space group. Electron microscopy techniques are used to understand the microstructure, elemental composition, and morphology of the composites. The dielectric properties are measured in the 1 Hz–1 MHz frequency range and 40–400 °C temperature range. Composite with x = 0.1 (ε′ ≈ 170, tan δ = 0.08 at 1 kHz) and 0.2 (ε′ ≈ 390, tan δ = 0.07 at 1 kHz) has better dielectric properties than the parent Ba0.8Sr0.2TiO3 ferroelectric (ε′ ≈ 125, tan δ = 0.16 at 1 kHz) and CoFe2O4 ferrimagnetic phases (ε′ ≈ 375, tan δ = 0.72 at 1 kHz), respectively. Composite with 10% cobalt ferrite has the highest saturation polarization (2.1 μC cm−2), the highest remanent polarization (0.9 μC cm−2), and coercive field (23.9 kV cm−1) compared to ferroelectric phase followed by x = 0.2 composite (PS = 1.6 μC cm−2, Pr = 0.8 μC cm−2, and EC = 19.2 kV cm−1). Composite with x = 0.2 shows the highest magnetic coercive field of 1.96 kOe. Hence, this article advocates that 20% ferrite in the composites is the optimized composition for multiferroic applications. The present study will help to explore piezoelectric, magnetostrictive, and magnetoelectric properties of (x)CoFe2O4–(1−x)Ba0.8Sr0.2TiO3 for the technological application.

Study of Structural, Dielectric, Electrical and Optical Properties of the Sr3CuTi4O12 Ceramics

In the present investigation, the synthesis of the strontium copper titanate [Formula: see text] ceramic by the cost-effective solid-state reaction was reported. The structural analysis suggests a single-phase tetragonal crystal symmetry with space group P4/mmm. The average crystallite size and mechanical compressive microlattice strain are found to be 65.8[Formula: see text]nm and 0.000594, respectively. The study of the field emission scanning electron microscope (FESEM) micrograph suggests that grains and grain boundaries are uniformly distributed on the sample surface with less porosity. The study of Raman lines suggests the presence of all constituent elements, which is well supported by EDAX analysis. The UV–Vis spectroscopy analysis shows that the bandgap of SCTO is about 3.2[Formula: see text]eV suitable for photovoltaic and other higher-temperature sensor applications. The decrease of dielectric constant with frequency supports the reduction of space charge polarization. The modulus analysis suggests that the immobile charge carriers at lower and defects and oxygen vacancies at higher temperatures are responsible for the thermally activated conduction process. The calculated activation energies are 4.54[Formula: see text]meV, 4.40[Formula: see text]meV, 3.39[Formula: see text]meV and 3.29[Formula: see text]meV at 1[Formula: see text]kHz, 10[Formula: see text]kHz, 100[Formula: see text]kHz and 1[Formula: see text]MHz; the decrease with the rise of the frequency confirms a thermally activated conduction process. Thermistor constant [Formula: see text], sensitivity factor [Formula: see text] and stability factor of the sample were calculated, which confirms the characteristics of the NTC thermistor. The Nyquist and Cole–Cole semicircular arcs confirm NTCR character and are found to be suitable applications for energy storage devices and thermistors.

Evaluation of photocatalytic efficacy of biosynthesized tetragonal SnO2 nanoparticles

Present report portrays, Ocimum Basilicum leaf extract (OBLE) mediated Tin (IV) oxide nanoparticles [SnO2@OBLE NPs] were synthesized in a cost-effective and environmental benign way. Rietveld refinement study of X-ray diffraction profile revealed the tetragonal rutile type crystal symmetry belonging to P4/2mnm space group. FTIR spectra showed hydroxyl (–OH) humps at 3443 cm−1 and 1630 cm−1 thereby confirming presence of methanolic phytochemicals which act as stabilizing, reducing and capping agents. FESEM micrograph of SnO2@OBLE NPs depicted non-uniform granular distribution with an average size of 23.29 ± 1.09 nm. SnO2@OBLE NPs illustrated potential candidature as a photocatalyst for degradation of natural red (NR) dye under UV light. The degradation efficiency was found to be 99.9 % at 150 min with a rate constant (k) of 0.0767 min−1.

Influence of Cr substitution on structural, optical, and magnetic properties of La2SrFe2O7: Their application as a photocatalyst for the degradation of Rhodamine B dye

A new n = 2 Ruddlesden-Popper (RP) series La2SrFe2-xCrxO7 (x = 0.0, 0.2, 0.4, 0.6 and 0.8) has been prepared via Sol-gel Pechini method, and their structural, optical, and the magnetic characterization was done. Furthermore, we are for the first-time reporting on the photo-catalytic degradation of a dye by a complete n = 2, La2SrFe2-xCrxO7 RP series. Rietveld refinement analysis confirms the formation of single-phase compounds with tetragonal crystal symmetry and I4/mmm space group. The results indicate a steady decrease in unit cell parameters and cell volume with Cr3+ doping. Dominant anti-ferromagnetic (AFM) interactions were observed in all the phases and the appearance of weak ferromagnetic (FM) interactions takes place owing to the Fe3+―O―Cr3+ FM interaction with Cr3+ doping. The χM−FC curve for x = 0.8 phase shows the magnetization reversal (MR) phenomenon and becomes zero at Tcomp ∼127 K and the value becomes negative on further decreasing the temperature. The MR phenomenon is discussed in terms of the competing Fe3+―O―Fe3+, Fe3+―O―Cr3+, and Cr3+―O―Cr3+ super-exchange interactions. Enhanced photocatalytic activity for the degradation of Rhodamine B (RhB) dye was obtained for x = 0.2 substituted phase, displaying a ∼99% degradation of dye in 30 min followed by ∼83%, ∼75%, ∼64% and ∼61% by x = 0.4, 0.0, 0.8 and 0.6 phases respectively in the same time interval. The results are explained in terms of crystallite size, the narrowing of band gap with Cr3+ substitution, and based on of recombination of charge carriers which, are in good agreement with the results of Photoluminescence (PL) emission intensity spectra.

Dependence of the Elastic Stiffness Tensors of PETN, α‐RDX, γ‐RDX, ϵ‐RDX, ϵ‐CL‐20, DAAF, FOX‐7, and β‐HMX on Hydrostatic Compression

AbstractThe dependence of the components of the elastic stiffness tensors (or elastic constants) of the organic explosives PETN, RDX, CL‐20, DAAF, FOX‐7, and HMX on hydrostatic pressure up to 10 GPa have been computed using dispersion‐corrected density functional theory. We report the evolution of lattice parameters and the non‐zero stiffnesses for the tetragonal, orthorhombic, and monoclinic crystal symmetries. Linear and quadratic dependencies of the components of the elastic stiffness tensors on volumetric compression and hydrostatic pressure are tabulated for use in single crystal plasticity models.

Anomalously High Ionic Conductivity of Li2SiS3-Type Conductors.

Solid-state electrolytes that exhibit high ionic conductivities at room temperature are key materials for obtaining the next generation of safer, higher-specific-energy solid-state batteries. However, the number of currently available crystal structures for use as superionic conductors remains limited. Here, we report a lithium superionic conductor, Li2SiS3, with tetragonal crystal symmetry, which possesses a new three-dimensional framework structure consisting of isolated edge-sharing tetrahedral dimers. This species exhibits an anomalously high ionic conductivity of 2.4 mS cm-1 at 298 K, which is 3 orders of magnitude higher than the reported ionic conductivity for its orthorhombic polymorph. The framework of this conductor consists mainly of silicon, which is abundant in natural resources, and its further optimization may lead to the development of new solid-state electrolytes for large-scale applications.

MAELAS 2.0: A new version of a computer program for the calculation of magneto-elastic properties

MAELAS is a computer program for the calculation of magnetocrystalline anisotropy energy, anisotropic magnetostrictive coefficients and magnetoelastic constants in an automated way. The method originally implemented in version 1.0 of MAELAS was based on the length optimization of the unit cell, proposed by Wu and Freeman, to calculate the anisotropic magnetostrictive coefficients. We present here a revised and updated version (v2.0) of MAELAS, where we added a new methodology to compute anisotropic magnetoelastic constants from a linear fitting of the energy versus applied strain. We analyze and compare the accuracy of both methods showing that the new approach is more reliable and robust than the one implemented in version 1.0, especially for non-cubic crystal symmetries. This analysis also helps us find that the accuracy of the method implemented in version 1.0 could be improved by using deformation gradients derived from the equilibrium magnetoelastic strain tensor, as well as potential future alternative methods like the strain optimization method. Additionally, we clarify the role of the demagnetized state in the fractional change in length, and derive the expression for saturation magnetostriction for polycrystals with trigonal, tetragonal and orthorhombic crystal symmetry. In this new version, we also fix some issues related to trigonal crystal symmetry found in version 1.0. Program summaryProgram title: MAELASCPC Library link to program files:https://doi.org/10.17632/gxcdg3z7t6.2Developer's repository link:https://github.com/pnieves2019/MAELASCode Ocean capsule:https://codeocean.com/capsule/2689126Licensing provisions: BSD 3-clauseProgramming language: Python3Journal reference of previous version: P. Nieves, S. Arapan, S.H. Zhang, A.P. Kądzielawa, R.F. Zhang and D. Legut, Comput. Phys. Commun. 264, 107964 (2021)Does the new version supersede the previous version?: YesReasons for the new version: To implement a more accurate methodology to compute magnetoelastic constants and magnetostrictive coefficients, and fix some issues related to trigonal crystal symmetry.Summary of revisions:•New method to calculate magnetoelastic constants and magnetostrictive coefficients derived from the magnetoelastic energy.•Correction of the trigonal crystal symmetry.•Implementation of the saturation magnetostriction for polycrystals with trigonal, tetragonal and orthorhombic crystal symmetry.•In the visualization tool MAELASviewer, we included the possibility to choose the type of reference demagnetized state in the calculation of the fractional change in length.Nature of problem: To calculate anisotropic magnetostrictive coefficients and magnetoelastic constants in an automated way based on Density Functional Theory methods.Solution method: In the first stage, the unit cell is relaxed through a spin-polarized calculation without spin-orbit coupling (SOC). Next, after a crystal symmetry analysis, a set of deformed lattice and spin configurations are generated using the pymatgen library [1]. The energy of these states is calculated by the Vienna Ab-initio Simulation Package (VASP) [2], including SOC. The anisotropic magnetoelastic constants are derived from the fitting of these energies to a linear polynomial. Finally, if the elastic tensor is provided [3], then the magnetostrictive coefficients are also calculated from the theoretical relations between elastic and magnetoelastic constants.Additional comments including restrictions and unusual features: This version supports the following crystal systems: Cubic (point groups 432, 4¯3m, m3¯m), Hexagonal (6mm, 622, 6¯2m, 6/mmm), Trigonal (32, 3m, 3¯m), Tetragonal (4mm, 422, 4¯2m, 4/mmm) and Orthorhombic (222, 2mm, mmm).

Anomalous viscosity of a chiral two-orbital superconductor in tight-binding model

We study the linear response of the deformation potential of a chiral two-orbital superconductor Sr $$_2$$ RuO $$_4$$ to the applied strain. This response rises due to the strain-induced modified interatomic distances. In the linear response theory, the deformation potential–deformation potential correlation function defines the full complex frequency-dependent viscosity tensor. We calculate the anti-symmetric part of this tensor, the phonon Hall viscosity, to consider the static and dynamical Hall responses. The static phonon Hall static enables us to distinguish the different topological phases of Sr $$_2$$ RuO $$_4$$ . We focus on two regimes: (a) the phonon Hall viscosity due to the changes in the hopping energies of the tight-binding Hamiltonian and is termed the normal phonon Hall viscosity and (b) the phonon Hall viscosity due to the variation in the amplitudes of the order parameter of the superconducting state that causes an anomalous momentum transport coefficient and is analogous to the one-dimensional odd isotropic part of the viscosity tensor of an incompressible fluid in two dimension space. In both cases, the tetragonal crystal symmetry which corresponds to the isotropy in the system plays an important role. We also investigate the effect of the crystal symmetry on the stability of the nontrivial topological phase.

Phase-field simulation of magnetic microstructure and domain switching in (Tb0.27Dy0.73)Fe2 single crystal

The morphotropic phase boundary (MPB), separating two ferroic phases with rhombohedral and tetragonal crystal symmetries, has been utilized extensively in ferroelectrics because it can lead to high-performance piezoelectricity. Recently, a parallel ferromagnetic MPB was experimentally reported and was suggested that the optimal point for magneto-mechanical applications might lies on the rhombohedral side. However, the insight of the domain structures and switching mechanism near ferromagnetic MPB is still unclear. In this work, phase-field micromagnetic microelastic modeling was employed to simulate the domain formation and magnetization switching of (Tb0.27Dy0.73)Fe2, whose composition is around the rhombohedral side of ferromagnetic MPB. The results show that four kinds of domains of the rhombohedral phase automatically form twins of {110} or {100} boundaries with 71° and 109° domain walls after a process of nucleation and growth. The rhombohedral domain evolution and phase volume fraction under the external field of 120 kA/m along different directions are investigated. In ferromagnetics subject to an alternating magnetic field, domain magnetization switches to cause a magnetization hysteresis loop and an associated butterfly magnetostriction loop with the alternating magnetic field.

Antilithiatic effect of watermellon (Citrullus lanatus) juice on Calcium Oxalate kidney stones

Background: Nephourolithiasis is a term refers to kidney stones formation, due to aggregation of minerals leading to the development of crystalluria in kidneys or any part of the urinary tract system. Many herbs were used to fragment and crush renal calculi. Habitually, it is noted that people who suffer from kidney problems are advised to eat large quantities of watermellon fruit then, the patient feels healing, without knowing the scientific reason for this improvement. Objectives The current study was designed to investigate the antilithiatic effects of Fresh Watermelon Juice (FWJ) on calcium oxalate kidney stones. Methods Direct exposure technique between FWJ and enucleate stons was used. The pH, and electrical conductivity (EC) of the exposure solution in addition to the chemical and morphological properties of the renal calculi before and after exposure using X-ray diffraction method (XRD) and scanning electron microscope (SEM) were investigated. Results: after 24 hours of submerging renal calculi with FWJ, the calculi appeared dissolved and fragmented with absence of solidity, rigidity and crystallization. The Ph Value and electrical conductivity (EC) of FWJ increased significantly after 24 hours of submerging the calculi increasing total soluble solids and ion concentrations in the solution. X-ray diffraction showed sharp peaks and intensity of of calcium oxalate calculi indicating a significant change in calculus compositionn, shape and crysallization within 48 hours of exposure FWJ.Scanning electron microscope images of treated and untreated renal calculi showed a significant difference in the shape of the crystals that have been transformed from their regular shape as bipyramids with tetragonal crystal point group symmetry to sculpted and un coordinated particles with the absence of a regular geometric shape of crystals with no clear crystallization patterns. Conclusion: Fresh watermellone juice appears to have a strong effect on the shape and composition and integrity of renal calculi which may aid its expulsion from the body.

Emergence of relaxor behavior along with enhancement in energy storage performance in light rare-earth doped Ba0.90Ca0.10Ti0.90Zr0.10O3 ceramics

Nano-sized light rare-earth (La, Pr, Nd, and Sm) doped Ba0.90Ca0.10Ti0.90Zr0.10O3 ceramics were synthesized to enhance the energy storage performance. The Rietveld study of bare and doped samples has shown tetragonal crystal symmetry and a single-phase perovskite structure. The rare-earth addition in Ba0.90Ca0.10Ti0.90Zr0.10O3 has resulted in a remarkable change in the microstructure of the doped samples. The addition of Nd in Ba0.90Ca0.10Ti0.90Zr0.10O3 lattice has resulted in optimum grain size and density among the five compositions. As a result of improvement in morphological characteristics in the Nd-doped sample, the dielectric, ferroelectric and piezoelectric characteristics were significantly enhanced. The Nd-doped sample has shown a relaxor behavior with a maximum dielectric constant of 10788 combined with a high saturation polarization of 41.88 μC/cm2. Further, the material has shown optimum electromechanical behavior with excellent aging characteristics. The obtained properties of Nd-doped Ba0.90Ca0.10Ti0.90Zr0.10O3 sample justifies its potential application in multi-layer energy storage capacitors.

Synergetic effect of rare-earths doping on the microstructural and electrical properties of Sr and Ca co-doped BaTiO3 nanoparticles

Single-phase BST-BCT ceramic doped with different rare-earth materials (La, Gd, Dy, and Yb) have been prepared using a modified mechano-chemical activation technique. The modified BaTiO3 doped with different rare-earths elements have manifested improved characteristics and desirable application in the field of high-power pulse capacitors. In this work, a comparative study has been performed to analyze the effect of different rare-earths on the dielectric, ferroelectric, piezoelectric and electrical breakdown strength of already optimized Sr and Ca co-doped BaTiO3 ceramic. As predicted from finite element simulation, the doping of rare-earth may lead to a change in microstructure and surface characteristics of Sr and Ca co-doped BaTiO3 ceramic and therefore, an enhancement in electrical characteristics of the material. The addition of various rare-earths with the same cationic charge but different ionic radii has resulted in a significant change in morphology of BST-BST ceramic. The XRD results indicate that all the samples retain the parent perovskite tetragonal crystal symmetry, and there is no substantial change in the crystal structure compared to the base material. The addition of rare-earths has resulted in a decrease in transition temperature and significant changes in the electrical properties of modified BaTiO3 ceramic. Lanthanum and Gadolinium doping have resulted in an overall improvement in electrical characteristics; however, Dysprosium and Ytterbium doping deteriorated the same characteristics, which is mainly attributed to a significant change in the microstructure of the materials.

Effect of gadolinium on the dielectric and pyroelectric behavior of Ba(Zr0.52Ti0.48)O3 ceramics

The microstructure, dielectric and pyroelectric properties of pure and Gd3+- doped barium zirconium titanate in the form of Ba(Zr0.52Ti0.48)O3 and (Ba1-xGdx)(Zr0.52Ti0.48)O3 (x = 0.1 and 0.2) were studied in this work. These ceramics were synthesized from solid state reaction method at 1050 °C. The patterns obtained from x-ray diffraction revealed the formation of perovskite phase with tetragonal crystal symmetry. As the concentration of Gd-ion increased, the value of temperature dependent dielectric constant varied whereas the Curie temperature of the ceramics shifted towards higher temperature side. The ceramic sample doped with Gd = 0.1 exhibited diffuse phase transition whereas other one showed relaxor like behavior. This result is attributed to unsystematic decrease in average grain size due to doping of Gd-ions. The temperature dependent pyroelectric current was negative at ∼150 °C for pure ceramics and at ∼200 °C for Gd-doped ceramics. This negative pyroelectric current represents the primary pyroelectric effect within that temperature.

Effect of codoping of Rare Earth ions on Microstructure and Band Gap of Ti0.98A0.01Gd0.01O2 (A: Sm/Eu/Tb) Nanostructures Synthesized by modified hydrothermal method

Sm3+, Eu3+, Tb3+ and Gd3+ ions have been incorporated in anatase TiO2 nanostructures by a hydrothermally modified sol gel method. XRD data analysis revealed the formation of pure anatase phase that crystallizes in the tetragonal crystal symmetry without any secondary phase. FTIR spectra indicate stretching vibrations of bonds in the nanostructures. The absorption peak centered at 568 cm−1 is related to the Ti-O-Ti stretching vibrations. Morphological studies and grain size estimation were performed by SEM measurements. SEM images depict nonuniform distribution of grains with a considerable variation in grain size. EDS measurements ensure chemical compositions in the samples. UV-visible absorption spectroscopy was used to study the optical properties. The doping of rare earth ions (Sm3+, Eu3+, Tb3+) leads to the variation in band gap of TiO2. Photoluminescence (PL) spectra indicate a significant change in the intensity on the doping of rare earth ions.

Evidence of compositional fluctuation induced relaxor antiferroelectric to antiferroelectric ordering in Bi0.5Na0.5TiO3–Bi0.5K0.5TiO3 based lead free ferroelectric

The high temperature electrical phase transitions of (1 − x) Bi0.5Na0.5TiO3–(x) Bi0.5K0.5TiO3 (x = 0.10, 0.15, 0.20, 0.25, 0.30 and 0.35) relaxor ferroelectrics have been investigated by employing the dielectric spectroscopy technique. The Rietveld refinement of the XRD patterns reveals the increase of the lattice distortion (c/a) from 1.001 to 1.006 in the tetragonal crystal symmetry (P4mm) with the increase of the BKT (x = 0.10, 0.15, 0.20, 0.25, 0.30 and 0.35) mole fraction. The different bonds vibration (Bi3+/Na+/K+–O and Ti4+–O) related to phonon modes have been studied by analyzing the Raman spectra. The relaxor antiferroelectric ordering temperature (Td: depolarization temperature) of Bi0.5Na0.5TiO3 (BNT) reduce from ~ 200 to ~ 91 °C with the increase of the BKT mole fraction. This observation is well correlated to the formation of polar nanoregions (PNRs) due to the compositional fluctuation in the local crystal structure. Also, Td varies with the frequency of the applied electric. It suggests the presence of the PNRs and, subsequently exhibits the relaxor ferroelectric behavior. The activation energy to activate the PNRs reduces from 2.573 to 2.383 meV with the increase of the BKT mole fraction in the solid solutions. Reduction in remanent electrical polarization and the electrical coercive field in temperature dependent ferroelectric hysteresis loops suggest the relaxor antiferroelectric behavior of the solid solutions (x ≥ 0.15) near the depolarization temperature.

Theoretical studies for identifying horizontal line nodes via angle-resolved density-of-states measurements: Application to Sr2RuO4

On the basis of the microscopic quasi-classical Eilenberger theory, we analyze the recent angle-resolved specific heat experiment carried out at low temperature for Sr$_2$RuO$_{4}$ to identify the superconducting gap symmetry, comprising either horizontal or vertical line nodes relative to the tetragonal crystal symmetry. Several characteristics, in particular, the landscape of the in-plane oscillation amplitude $A_4(B, T)$ with a definite sign for almost the entire $B$-$T$ plane are best explained by the horizontal line node symmetry, especially when the multiband effect and Pauli paramagnetic effect are taken into account. The present analysis of $A_4(B,T)$ with definite sign points to the presence of an anomalous field region at a lower temperature in the experimental data, whose origin is investigated. Our theory demonstrates the application and uniqueness of the field-rotating thermodynamic measurements in uncovering the precise gap structure for target materials.

Superconductivity in the presence of spin-orbit interactions stabilized by Hund coupling

The intraorbital repulsive Hubbard interaction cannot lead to attractive superconducting pairing states, except through the Kohn-Luttinger mechanism. This situation may change when we include additional local interactions such as the interorbital repulsion $U^\prime$ and Hund's interactions $J$. Adding these local interactions, we study the nature of the superconducting pairs in systems with tetragonal crystal symmetry including the $d_{xz}$ and $d_{yz}$ orbitals, and in octahedral systems including all three of $d_{xz}$, $d_{yz}$, and $d_{xy}$ orbitals. In the tetragonal case, spin-orbit interactions can stabilize attractive pairing channels containing spin triplet, orbital singlet character. Depending on the form of spin-orbit coupling, pairing channels belonging to degenerate, non-trivial irreducible representations may be stabilized. In the octahedral case, the pairing interactions of superconducting channels are found to depend critically on the number of bands crossing the Fermi energy.

Spontaneous Thermal Hall Effect in Three-dimensional Chiral Superconductors with Gap Nodes

Generic chiral superconductors with three-dimensional electronic structure have nodal gaps and are not strictly topological. Nevertheless, they exhibit a spontaneous thermal Hall effect (THE), i.e. a transverse temperature gradient in response to a heat current even in the absence of an external magnetic field. While in some cases this THE can be quantized analogous to the Quantum Hall effect, this is not the case for nodal superconductors in general. In this study we determine the spontaneous THE for tight binding models with tetragonal and hexagonal crystal symmetry with chiral $p$- and d-wave superconducting phase. At the zero-temperature limit, the thermal Hall conductivity $ \kappa_{xy} $ provides information on the structure of the gap function on the Fermi surface and the Andreev bound states on the surface. The temperature dependence at very low temperatures is determined by the types of gap nodes, point or line nodes, leading to characteristic power law behaviors in the temperature, as known for other quantities such as specific heat or London penetration depth. The generic behavior is discussed on simple models analytically, while the analysis of the tight-binding models is given numerically.

Synthesis, crystal structure and microwave dielectric properties of Sr2LnMgNbO7 (Ln = La, Nd, Sm) novel compounds with Ruddlesden-Popper structure

Sr2LnMgNbO7 (Ln = La, Nd, Sm) novel compounds were prepared via standard solid-state reaction method, and their crystal structures and microwave dielectric properties were systematically investigated for the first time. X-ray diffraction (XRD) results indicated that pure Sr2LaMgNbO7 and Sr2NdMgNbO7 ceramics were synthesized, while some additional diffraction peaks corresponding to the perovskite-type secondary phases were observed in the Sm composition. Rietveld analyses indicated that Sr2LnMgNbO7 (Ln = La, Nd) compounds belonged to the n = 2 type Ruddlesden–Popper structure with general formula of An+1BnO3n+1, and their space groups were confirmed to be I4/mmm with tetragonal crystal symmetry. The detailed structural information of Sr2LaMgNbO7 and Sr2NdMgNbO7 compounds were revealed and their corresponding microwave dielectric properties were evaluated.

Effect of vacuum and sulphur annealing on the structural properties of spray deposited Cu2SnS3 thin films

Cu2SnS3 thin films have been deposited by using non-vacuum spray pyrolysis technique on soda lime glass substrates from single aqueous solution containing all the constituents. The effect of post deposition annealing of the Cu2SnS3 thin films on the composition, structural, optical and electrical properties has been studied. The XRD study reveals that vacuum annealing of the thin film gives rise to the evolution of CuxSy secondary phases by the loss of elemental tin, while the annealing held at sulphur atmosphere increases the crystallinity of the film without giving rise to any secondary phases. The Cu2SnS3 phase with preferred orientation along the (112) crystal direction grew to greater extent upon sulphur annealing associated with an improvement in the optical band gap. From the Raman analysis it was observed that as-deposited films are dominated by the presence of tetragonal crystal symmetry of the Cu2SnS3 phase. Upon vacuum annealing the peak appearing at 474 cm−1 grows to greater extent which corresponds to CuS phase, and is in good agreement with the XRD spectra. Eventually its sulphur annealing gives the pure phase of Cu2SnS3 with dominating tetragonal crystal structure.