Tetragonal Research Articles

Enhancement in the optoelectronic and thermoelectric properties of the NaASb (A= Ca, Sr and Ba) Sodium Antimonides via switching from P4/nmm to P62 m symmetry

Structural, opto-electronic and thermoelectric properties of square and butterfly like structured NaASb (A = Ca, Sr and Ba) Sodium Antimonides in tetragonal and hexagonal symmetries (P4/nmm and P62 m) are investigated using of density functional theory (DFT). Structural properties are in good agreement with the reported outcomes. Cohesive energy per atom (−8.233 to −26.1004 for P4/nmm and −8.522 to −28.7306 for P62 m symmetry) and enthalpy of formation per atom (−0.9468 to −2.6800 for P4/nmm and −1.1721 to −2.8034 for P62 m symmetry) for these compounds reveals that these compounds are stable in both P4/nmm and P62 m symmetries and are more stable in P62 m space group as compare to P4/nmm symmetry. Electronic properties show that the transition from indirect to direct band gap nature occurs by replacement of Ca/Sr by Ba in P4/nmm symmetry while P62 m symmetry all the NaASb (A = Ca, Sr and Ba) compounds are direct bandgap semiconductors. The band gap values lie in the range of 0–1.393 in P4/nmm symmetry and 0.542 to 1.547, respectively, in P62 m symmetry. Electrical conductivity also reveals the semiconducting characteristics of these compounds. The study shows that the replacement of Ca by Sr and Ba reduces the band gap and the reduction in bandgap values is greater in P4/nmm symmetry as compared to P62 m. The outcome demonstrates that these compounds NaASb (A = Ca, Sr and Ba) are implicitly active optically in the infrared region and are capable of serving as the primary applicant for optoelectronic devices. Thermoelectric properties like Seebeck coefficient (−138.5 to 154.7 μV/K in P4/nmm, −36.5 to −125.3 μV/K in P62 m at 500 K), Power factor (1.33–3.05 GW/mK2s in P4/nmm, 0.152–0.322 GW/mK2s in P62 m at 500 K) and thermoelectric figure of merit ranges from 0.495 to 0.946 in P4/nmm and 0.016 to 0.260 in P62 m at 500 K shows that these compounds are potential candidates for thermoelectric application in P4/nmm symmetry.

Phase Equilibria in the Quasi-Ternary System Cu2Se-In2Se3-CuI and the Crystal Structure of the AIBIII2XVI3YVII Compounds, Where AI-Cu, Ag; BIII-Ga; XVI-Cl, Br, I; YVII-S, Se, Te

The quasi-ternary system Cu2Se-In2Se3-CuI has been investigated by x-ray diffraction and differential thermal analysis. The isothermal section at 770 K and the liquidus surface projection of the system have been built. For the first time, the primary crystallization regions, and the coordinates of the invariant and monovariant equilibria have been determined. In the system, the regions of the solid solutions based on the binary, ternary, and quaternary compounds have been investigated. The formation of the CuIn2Se3I quaternary compound, which melts congruently at 1213 K and has a homogeneity region of 15 and 9 mol.% CuI within the composition triangle has been established. For the first time, the crystal structures of CuGa2Te3I and AgGa2Te3Br compounds have been studied using a powder method. They crystallize in the tetragonal symmetry, Space Group I-4, a = 5.9147(4) Å, c = 11.952(2) Å for CuGa2Te3I; a = 6.2977(3) Å, c = 11.9473(7) Å for AgGa2Te3Br compound, respectively. The connection of their structures with the structures of the defective diamond-like semiconductors has been discussed.

Growth of epitaxial Bi0.5(Na1-xKx)0.5TiO3 films by hydrothermal reaction time and their characterization

The hydrothermally grown films can be used in various applications because of their relatively lower reaction temperature than the other growth methods. Bi0.5(Na1-xKx)0.5TiO3 films on SrTiO3 substrates are synthesized using the hydrothermal reaction to study its structural and piezoelectric response. The different morphological analysis of films by field emission scanning electron microscope shows the grains on films get through the dissolution-recrystallization process with Ostwald ripening. Also, the structural analyses are carried out using X-ray diffraction and transmission electron microscope which confirmed the formation of epitaxial films with their high crystallinity, and tetragonal symmetry under compressive strain. Through X-ray photoelectron spectroscopy, it was confirmed that the constituent elements and element ratios of BNKT vary according to the reaction time, and the piezoelectric and ferroelectric behaviors were confirmed through a piezoelectric force microscope and piezoelectric coefficient. A combination of the structural and piezoelectric measurements reveals that the reaction time affects the composition of our epitaxial film.

Studies of Structural, Optical, and Electrical Properties of Eco‐Friendly Complex Ferroelectrics: BaTiO3–Bi0.5Na0.5TiO3

Some lead‐free complex compounds containing the two perovskite compounds BaTiO3 and Bi0.5Na0.5TiO3 of chemical composition (Ba1–xBix/2Nax/2)TiO3 (x = 0, 0.05, 0.1, 0.15) are fabricated using a cost‐effective mixed oxide method. Synthesis and characterization (electrical, ferroelectric, and optical) of the above‐defined complex ferroelectrics are reported in this article. Analysis of the X‐ray diffraction data/pattern reveals the formation of phase pure compounds with tetragonal symmetry. Determination of particle size is done using the Scherrer formula. A morphology study of sintered (at 1100 °C) pellets indicates that average grain size decreases with an increase in Bi/Na content of Bi0.5Na0.5TiO3. Studies of Fourier transform infrared spectroscopy and ultraviolet–visible–near‐infrared spectroscopy reveal the type of chemical bonds present in the materials. The energy bandgaps of the compounds are found to be suitable for optical device applications. The frequency and temperature dependence of the dielectric study reveals that the dielectric constant increases and loss tangent decreases with an increase in Bi/Na content of Bi0.5Na0.5TiO3. The analysis of the I–V plot and the field‐dependent polarization (P–E hysteresis loop) provide the low leakage current and existence of ferroelectricity at room temperature, respectively.

The effect of interfacial charge-induced multiferroic properties of Bi0.993La0.007FeO3/BaTiO3 bilayer thin films: Performance modulation and energy storage applications

Multifunctional and multiferroic materials assure a tantalizing perspective of applications in next-generation microelectronics, memory, energy harvesting, and energy storage technologies. The current study aims to deposit a bilayer thin film of BLFO/BTO with varying top layer (BLFO) thickness on n-type Si and Pt/Ti/SiO2/Si (Pt-Si) substrate by the PLD technique. Bilayer films with dense and packed microstructures show evidence of both tetragonal (T) and rhombohedral (R) symmetry. The bilayer films exhibit remarkably enhanced saturation magnetization of 35.9 emu/cm3 and improved maximum polarization of 34 μC/cm2 at RT compared to single-layer films. Moreover, the higher top layer thickness (BTO/BLFO3) hetero-structures achieved a high recoverable energy storage density of 11.65 J/cm3 with an energy efficiency of 85 % simultaneously. These films display excellent energy storage performance and produce a maximum power density of 0.9 MW/cm3 at 100 Hz. Further, the leakage current density of BLFO/BTO3 film is found ∼102 times lower than the monolayer BTO thin film suggesting the lower oxygen vacancies, defects, and impurities in the bilayer stacked films with higher top layer thickness. The drop in leakage current density, slim hysteresis loop, and enhancement in large saturation polarization for BTO/BLFO3 highlight the improved result demonstrating the interface effect and coupling between ferroelectric and magnetic properties. Hence, the acquired ferroelectric and magnetic properties are promising for spintronic devices and energy storage capacitor applications.

Structural, Magnetocaloric, and Magnetic Properties in Heusler Ni50Mn35In10X5 (X = Ga, Fe and Al) Alloys

The structural, magnetocaloric, and magnetic characteristics in Heusler Ni50Mn35In10X5 (X = Ga, Fe, and Al) alloys were examined using X-ray diffraction and field-dependent magnetization measurements. All samples exhibited a mixture structure of cubic L21 and tetragonal L10 and underwent second-order magnetic transitions at TC(Al5) = 220 K, TC(Ga5) = 252 K, and TC(Fe5) = 298 K. The Ga5 alloy exhibited structural change as indicated by a thermal hysteresis that may be seen in the saturation magnetic field in the M(T) dependences. The transition at the TC point from a ferromagnetic to a paramagnetic state caused a drop in magnetization, supported by thermal hysteresis, at a low magnetic field (0.01 T). On the other hand, the Fe5 alloy presented a gradual decrease in magnetization with similar hysteresis behavior, also at a low magnetic field (0.01 T), whereas at 0.1 T of field, no features characteristic of this transition were detected. This could be due to a large difference in the metallic radius of Fe compared to that of In. Otherwise, magnetic investigations demonstrated that the replacement of In with Al may cause the structural transformation temperatures and TC to be shifted to low temperatures. The present results imply that the structural transformation temperatures and the transition itself are highly dependent on chemical composition. Furthermore, under a magnetic field change of 5 T, the maximum magnetic entropy changes of 0.6 J/kg K, 1.4 J/kg K, and 2.71 J/kg K for the Ga5, Fe5, and Al5 alloys, respectively, were determined by their TC. Refrigeration capacity values were found to be 25 J/kg, 74 J/kg, and 98 J/kg at µ0∆H = 5 T. These ribbons are viable candidates for multifunctional applications due to their cheaper cost and their physical characteristics disclosed during the magnetostructural transition, which takes place close to the room temperature.

Structural and vibrational properties of cage-type Sc5Ru6Sn18 superconductor under pressure using synchrotron X-ray diffraction and Raman spectroscopy

We report detailed structural investigations of cage-type quasi-skutterudite compound Sc5Ru6Sn18 using synchrotron single-crystal and powder x-ray diffraction. Single-crystal x-ray diffraction studies at ambient temperature revealed that the Sc5Ru6Sn18 compound has a tetragonal symmetry in the I41/acd space group setting with a = 13.58Å and c = 27.14Å, similar to other R5Rh6Sn18 (R = Y, Sc, Lu) cage-type compounds. The electrical resistivity ρ(T) revealed the presence of a sharp superconducting (SC) transition at Tc = 4.07K. The ρ(T) of Sc5Ru6Sn18 above Tc shows a smooth decrease with decreasing temperature without any evident anomalies. Systematic temperature dependent synchrotron x-ray powder diffraction (XRPD) studies covering 400 to 110K shows that the Sc5Ru6Sn18 system remain in the tetragonal I41/acd structure in this temperature range without any anomalous behaviour in the unit-cell parameters. High-pressure (HP) synchrotron XRPD revealed a smooth reduction in the unit-cell parameters up to ~7GPa which can be well described by a third-order Birch-Murnaghan equation providing the bulk modulus of the system to be ~102.6GPa. This system is found to several Raman modes below 300cm-1. We could follow the pressure evolution of four Raman modes, all of which show a smooth hardening with pressure up to ~7GPa. Our results call for systematic HP studies of the SC properties of the title system.

Structure, dielectric and ferroelectric Properties of (1-x)K0.5Na0.5NbO3 – xBi0.5Na0.5TiO3(0 ≤ x≤ 0.1) Solid Solution

In this study, we prepared lead-free (1-x)K0.5Na0.5NbO3 – xBi0.5Na0.5TiO3 ceramics (KNNBTx) with x = 0, 0.025, 0.05, 0.075, 0.1 using the conventional solid-state reaction method. Scanning electron microscopy analysis revealed dense ceramics with a notable decrease of the average grain size from 3 μm for x = 0–0.3 μm for x ≥ 0.050. X-ray diffraction pattern refinement unveiled that the pure KNN possessed an orthorhombic Amm2 symmetry. In contrast, the KNNBT0.100 composition displayed a tetragonal P4mm symmetry, while the KNNBT0.025 composition exhibited a monoclinic Pm symmetry, suggesting the stabilization of an intermediate phase between the orthorhombic and tetragonal symmetries for x = 0.025. Dielectric measurements indicated that the introduction of small cations in A and B sites of the KNN matrix induced a diffusive phase transition. According to the modified Curie–Weiss law (named also Uchino and Nomura function), the degree of diffuseness (γ) increased from γ = 1.45 to γ 1.74 with increasing x. Raman spectroscopy revealed a frequency upshift of the vibration modes along with broadening of the modes as the NBT composition increased, indicating increased structural disorder in the perovskite structure. Temperature-dependent Raman spectra exhibited the persistence of certain modes at higher temperatures due to the off-centering of cations at A and B sites, a result of the induced substitution-induced disorder in the KNN matrix. Temperature dependent of Raman modes’ frequency have shown substantial modifications at temperatures close to the critical temperatures identified by dielectric measurements. Ferroelectric measurements demonstrated that the incorporation of NBT into the KNN matrix led to significant alterations in the polarization and ferroelectric characteristics of the parent ceramic (pure KNN). As the NBT content increased, the remanent polarization decreased from 13.1 to 3.6 μC/cm2, and the P-E curves became pinched/distorted, indicating a disruption in the long-range order of KNN due to structural and grain size modifications.

Synthesis of new oxygen deficient triple layered perovskite oxides LaSr3Fe3-xCrxO10-δ (x = 0.0, 0.2, and 0.5): Structural, optical, magnetic and photocatalytic properties

In the present study, new oxygen deficient triple layered Ruddlesden-Popper (RP) phases LaSr3Fe3-xCrxO10-δ (x = 0.0, 0.2, and 0.5) have been prepared via sol-gel procedure. The prepared n = 3 RP phases were characterized with various characterization techniques in order to visualize the effect of Cr3+ doping on structural, optical, magnetic and photocatalytic properties. Rietveld structural refinements showed that all the phases crystallized in the I4/mmm space group with tetragonal symmetry. Dominant anti-ferromagnetic (AFM) interactions (Fe3+―O―Fe3+ and Fe4+―O―Fe4+) were noticed in each of these oxygen deficient triple layered phases with presence of weak ferromagnetic (FM) interactions. The decline in the values of Neel temperature (TN) with Cr doping has been interpreted on the basis of increase in FM Fe3+―O―Cr3+ interactions. The energy band gap values (Eg) of all the synthesised oxygen deficient phases vary from 1.63 to 1.73 eV, which makes them excellent photocatalysts for dye decontamination. Furthermore, the photocatalytic performance of the prepared phases was assessed by utilizing rhodamine B (RhB) dye as model dye pollutant. It was found that LaSr3Fe2.5Cr0.5O9.17 photocatalyst showed excellent results in the removal of RhB dye. As a result, we were further encouraged to extend the degradation to some other organic dyes such as methylene blue (MB), methyl orange (MO) and their mixture (RhB + MB + MO).

Crystal Field Engineering Yields New 3D Layered Solid Solution Phosphors (Ca/Sr)4MgAl2Si3O14:Eu2+ for White-Light-Emitting Diode Full-Spectrum Lighting.

The cation-equivalent substitution strategy has the ability to manipulate the luminescence color of phosphors and enhance their overall luminescence performance. A series of novel yellow feldspar-type 3D layered phosphors (Ca1-ySry)4MgAl2Si3O14:xEu2+ were synthesized using a high-temperature solid-state reaction. The solid solution phosphors belong to a tetragonal crystal system with a space group of P4̅21m and cell parameters of a = b = 7.75407-7.91794 Å, c = 5.04299-5.22543 Å, and V = 303.166-327.602 Å3. Under near-ultraviolet (n-UV) excitation, the luminescence color of the phosphor undergoes modulation from yellow-green (530 nm) to blue (467 nm) as the Sr2+ ion substitution ratio increases. This modulation is attributed to the gradual decrease in crystal field splitting energy. Additionally, both the Stokes shift and the full width of the luminescence spectra decrease. Furthermore, there is an increase in the quantum yield (QY) from 45.50 to 60.73%. Finally, the fabricated white-light-emitting diode devices emitted warm white light and achieved high Ra (Ra = 94, 96.6, 92.7) and low correlated color temperature (CCT = 3486, 3430, 3788 K), indicating that the prepared solid solution phosphors can be used as candidate materials for WLED lighting.

Compositional induced structural phase transitions in (1 − x)(K0.5Na0.5)NbO3–x(Ba0.5Sr0.5)TiO3 ferroelectric solid solutions

Ferroelectric materials exhibiting switchable and spontaneous polarization have strong potential to be utilized in various novel electronic devices. Solid solutions of different perovskite structures induce the coexistence of various phases and enhance the physical functionalities around the phase coexistence region. The construction of phase diagrams is important as they describe the material properties, which are linked to the underpinning physics determining the system. Here we present the phase diagram of (K0.5Na0.5NbO3)–(Ba0.5Sr0.5TiO3) (KNN-BST) system as a function of composition and their associated physical properties. Lead-free (1 − x)KNN–xBST (0 ≤ x ≤ 0.3) solid solution ceramics were synthesized by conventional solid-state reaction technique. The X-ray diffraction and Raman spectroscopic studies indicate composition-dependent structural phase transitions from an orthorhombic phase for x = 0 to orthorhombic + tetragonal dual-phase (for 0.025 ≤ x ≤ 0.15), then a tetragonal + cubic dual-phase (x = 0.2) and finally a cubic single phase for x ≥ 0.25 at room temperature (RT). Among these, the orthorhombic + tetragonal dual-phase system shows an enhanced value of the dielectric constant at room temperature. The phase transition temperatures, orthorhombic to tetragonal (TO-T) and tetragonal to cubic (TC), decrease with the increase in BST concentrations. The ferroelectric studies show a decrease of both 2Pr and EC values with a rise in BST concentration and x = 0.025 showed a maximum piezoelectric coefficient.

Cu2ZnGeSe4 single crystals: Growth, structure and temperature dependence of band gap

This work describes the production of single crystals of the semiconducting quaternary compound Cu2ZnGeSe4 using a gas chemical method in which iodine was used as a transporter. For all the synthesized samples, their phase state, crystal structure syngony and lattice constants were refined. The unit cell of the studied compound is characterized by tetragonal symmetry. The transmission spectrum was applied to calculate the band gap, which is depicted as temperature function in 20–300 K range. It was fixed that the band gap increases by 12% with decreasing temperature.

Synthesis and Luminescent Properties of Barium Molybdate Nanoparticles.

BaMoO4 was obtained via facile mechanochemical synthesis at room temperature and a solid-state reaction. An evaluation of the phase composition and structural and optical properties of BaMoO4 was conducted. The influence of different milling speeds on the preparation of BaMoO4 was explored. A shorter reaction time for the phase formation of BaMoO4 was achieved using a milling speed of 850 rpm. A milling speed of 500 rpm led to partial amorphization of the initial reagents and to prolongation of the synthesis time of up to 3 h of milling time. Solid-state synthesis was performed via heat treatment at 900 °C for 15 h. X-ray diffraction analysis (XRD), infrared (IR) and UV diffuse reflectance (UV-Vis) and photoluminescence (PL) spectroscopy were carried out to characterize the samples. Independently of the method of preparation, the obtained samples had tetragonal symmetry. The average crystallite sizes of all samples, calculated using Scherrer's formula, were in the range of 240 to 1540 Å. IR spectroscopy showed that more distorted structural MoO4 units were formed when the compound was synthesized via a solid-state reaction. The optical band gap energy of the obtained materials was found to decrease from 4.50 to 4.30 eV with increasing crystallite sizes. Green- and blue-light emissions were observed for BaMoO4 phases under excitation wavelengths of 330 and 488 nm. It was established that the intensity of the PL peaks depends on two factors: the symmetry of MoO4 units and the crystallite sizes.

Coexistence of five domains at single propagating interface in single-crystal Ni[sbnd]Mn[sbnd]Ga shape memory alloy

Coexistence of both austenite and martensite during phase transformation is a common feature of all Shape Memory Alloys (SMAs). The martensite has different variants featuring characteristic deformations rotationally linked to each other due to the symmetries of the austenite parent phase, and the martensite variants can form twins with different mean characteristic deformations. Multiple-domain microstructures (consisting of austenite, martensite twins and individual martensite variants) evolve collectively within an SMA sample during the phase transformation, contributing thus to the material's macroscopic response (e.g., its global deformation). Particularly, the multiple domains can exist at the diffuse austenite-martensite interface nucleating and propagating in a single crystal in certain conditions. This implies an energy barrier for this interfacial structure, influencing the interface kinetics and the driving force (energy dissipation) of the phase transformation. In this paper, we report an experimentally observed interface consisting of five domains (austenite, one martensite variant and three twins) in a Ni–Mn–Ga single-crystal initially consisting of one martensite variant and subjected to a uniaxial thermal gradient. The compatibility analysis (performed from the characteristic strains of the three martensite variants having approximately a tetragonal symmetry) reveals that the five-domain interface is not a perfectly compatible pattern like the basic habit plane (consisting of only one twin compatible with austenite). However, its level of non-compatibility is similar to that of the quite common X-interface (four-domain coexistence) which is observed in many SMAs. Further, the significant effects of the thermal loading path and the material initial state (the initial martensite variant) on the domain pattern formation are demonstrated and analyzed. The experimental observation and the theoretical analysis of the domain patterns can provide hints to better understand diffuse interface kinetics and phase transformation hysteresis.

Formation of a Body-Centered Tetragonal Structure With High Magnetic Anisotropy and Coercivity in Fe–Co–V Films With High C Contents

A high amount of C (0–20 at.%) was added to Fe–Co–V films via sputtering to transform their body-centered cubic (bcc) structure to a face-centered cubic (fcc) lattice through a body-centered tetragonal (bct) structure. The Fe–Co films without V retained a bcc or bct crystal structure with an axial ratio ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c/a</i> ) of 1.03 even at high C contents close to 20 at.%. Meanwhile, in the Fe–Co films containing 10 at.% of V, a bct structure with 1.06 ≤ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c/a</i> ≤ 1.30 was formed after adding 5–12 at.% of C, which was subsequently transformed to an fcc structure with increasing C content. The saturation magnetization of the Fe–Co–V–C films with the bct structure was approximately 1000–1500 kA/m, and their uniaxial magnetic anisotropy constant ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">u</sub> ) was approximately 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> J/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> (the films with high Fe contents exhibited high <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">u</sub> values). The bct Fe–Co–V–C films with high <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">u</sub> were microfabricated into nanodot array patterns via electron beam lithography. The coercivity of the pattern increased with decreasing dot size, and that of the pattern with a dot diameter of 85 nm was nearly an order of magnitude higher than that of the continuous film.

Growing crystals and studying structure and electronic properties of Cu2ZnGe(SхSe1-x)4 compositions

Single crystals of Cu2ZnGeSe4 and Cu2ZnGeS4 solid solutions were developed and successfully obtained using the chemical vapor transfer method, with iodine acting as a transporter. The structure, compositional dependences of lattice parameters, pycnometric and X-ray densities and microhardness were determined. The chemical composition determined by the X-ray microanalysis satisfactorily corresponds to the nominal one with a tolerance of ±5 %. The XRD analysis showed that all the obtained compounds and their solid solutions have unit cell described by tetragonal symmetry. The attice parameters were found to be а = 5.342 ± 0.005 Å, с = 10.51 ± 0.01 Å for the Сu2ZnGeS4 compound and а = 5.607 ± 0.005 Å, с = 11.04 ± 0.01 Å for the Cu2ZnGeSe4, respectively. Structural studies confirmed the validity of the Vegard's law in relation to the obtained samples. The pycnometric densities of ∼4.28 g/cm3 for the Cu2ZnGeS4 and ∼5.46 g/cm3 for the Cu2ZnGeSe4 were found to be slightly less than their X-ray densities of ∼4.32 g/cm3 and ∼5.52 g/cm3, respectively. The maximum microhardness of ∼398 kg/mm2 for these solid solutions corresponds to x = 0.60. The melt point of the solid solutions increases from ∼1180 °C for the Сu2ZnGeSe4 up to ∼1400 °C for the Сu2ZnGeS4. Based on X-ray fluorescence analysis and DTA data, the phase diagram of the Cu2ZnGeSe4-Cu2ZnGeS4 system was constructed. Analysis of the obtained diagram indicates its first type according to Rozbom's classification.

Exploring the performance of T-graphene for the anode of Mg-ion and Ca-ion batteries: A first-principles study

Due to the growing need for high-capacity ion storage batteries, researchers are exploring new categories of electrode materials with superior electrochemical properties. In this investigation, a tetragonal symmetry of carbon named T-graphene has been taken into consideration as an anode material for Mg and Ca ion batteries for its superior electrical characteristics. To comprehend the adsorption behavior, charge transfer, and anodic properties of T-graphene, density functional theory has been employed. Initially, the most favorable adsorption sites for Mg/Ca insertion on the T-graphene have been identified and it found that bridge and octagonal hollow sites show high adsorption behavior with energy of about −1.99 and −4.86 eV, respectively. A significant amount of charge (Hirshfeld) about 0.24e and 0.79e transfer from Mg and Ca to T-graphene, respectively. When Mg/Ca is inserted, the electronic structure calculations demonstrate that T-graphene acts metallically. A very high specific capacity is found at about 1737.13 and 1985.30 mAh/g for Mg and Ca ion batteries, respectively. Moreover, the average open-circuit voltages for Mg are 0.65 V and 1.51 V for Ca. Therefore, it is assumed that T-graphene may be used as high-capacity anode material for Mg and Ca ion battery.

Heavy-Fermion Properties of Yb2Pd2SnH≈2

A hydride of Yb2Pd2Sn could be synthesized with approximately 2 H atoms per f.u. The hydrogenation leads to a volume expansion while preserving the tetragonal symmetry (P4/mbm). The lattice reaction is strongly anisotropic, and the 5% expansion in c is partly compensated by the 0.5% compression in a. The hydride is paramagnetic at least down to 0.5 K. Yb remains at or very close to the 3+ (4f13) state, as in Yb2Pd2Sn. Specific heat C/T vs. T shows an upturn existing already in Yb2Pd2Sn, but it is much more pronounced in the hydride (1.8 J/mol f.u. K2 for T → 0, i.e., more than twice higher than in its precursor). This is interpreted as lowering the Kondo temperature due to H bonding.

Third order nonlinear optical, dielectric, photoluminescence and thermal analysis of Gd3+ doped glycine copper chloride (GCC) crystals

In the present investigations, metal-organic third order nonlinear optical (NLO) crystals of glycine copper chloride (GCC) and gadolinium (Gd) doped GCC with molecular formula (C2H5NO2CuCl2)1−x [Gd(NO3)3]x, where [x = 0.05, 0.10, 0.20] have been successfully grown. The growth of these semi-organic crystal compositions has been achieved at room temperature by slow solvent evaporation technique. The crystals exhibit excellent properties which get confirmed by various characterization studies like single crystal X – ray diffraction (SCXRD), powder X – ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), ultraviolet visible spectroscopy (UV – Vis), photoluminescence (PL) spectroscopy, thermal analysis, electrical and nonlinear optical studies. SCXRD confirms that the grown crystal crystallizes in tetragonal crystal system having space group P42/mnm. The PXRD shows the appearance of sharp and strong peaks which refers to the good crystallinity and phase purity of the grown crystals. FTIR was recorded in order to identify various expected functional group. Linear optical behaviour using UV – Vis confirms the compositions to have good optical transmission in the entire visible region and lower cutoff wavelength ranging between 225 and 244 nm which is essential parameter for developing optoelectronic devices. The band gap value comes out to be in the range of 5.43 – 5.53 eV. The grown crystals possess excellent thermal stability. Results of dielectric studies conducted as a function of temperature divulged the electrical properties of crystals. Third – order nonlinear optical (TONLO) response have been observed using Z – scan setup. The calculated TONLO parameters n2, β, and χ(3) shows large value suggests that grown compositions can be used in practical non linear optical device applications.

Formation mechanism of composite secondary phase particles in a solution-treated Si-modified Zircaloy-4

Zr-Si binary precipitates affect mechanical and corrosion properties of Si-modified Zircaloy-4. In this study, composite secondary phase precipitates, having a core of C16 Zr2Si precipitate semi-coated with C15 Zr(Fe,Cr)2 Laves phase, were analysed as observed after solution treatment of experimental Si-modified Zircaloy-4. Crystallographic orientation relationship between the body-centred tetragonal (BCT) Zr2Si and face-centred cubic (FCC) Zr(Fe,Cr)2 Laves phase regions was determined to be (101¯)C16 // (110)C15 and [11¯1]C16 // [11¯1]C15. Two regions formed an incoherent interface accommodating about 30 % misfit strain, calculated by Bramfitt two-dimensional lattice mismatch criterion. The mechanism of formation of composite precipitates was described which, in turn, outlines the way for manipulating microstructure of composite precipitates to further optimise mechanical properties of Si-modified Zircaloy-4.