Temperature Dependence Of Lattice Parameters Research Articles

Magnetoelastic Coupling Evidence by Anisotropic Crossed Thermal Expansion in Magnetocaloric RSrCoFeO6 (R = Sm, Eu) Double Perovskites.

Double perovskite oxides, characterized by their tunable magnetic properties and robust interconnection between the lattice and magnetic degrees of freedom, present an enticing foundation for advanced magnetic refrigeration materials. Herein, we delve into the influence of rare-earth elements on RSrCoFeO6 (R = Sm, Eu) disordered double perovskites by examining their structural, electronic, magnetic, and magnetocaloric properties. Temperature-dependent synchrotron X-ray diffraction analysis confirmed the stability of the orthorhombic phase (Pnma) across a wide temperature range. X-ray photoemission spectroscopy revealed that both Sm and Eu are in the 3+ state, whereas multiple states for Co2+/3+ and Fe3+/4+ are identified. The magnetic investigation and magnetocaloric effect (MCE) analysis brought to light the presence of a long-range antiferromagnetic (AFM) order with a second-order phase transition (SOPT) in both samples. The maximum magnetic entropy change ΔSMmax was approximately 0.9 J/kg K for both samples at applied field 0-7 T, manifesting prominently above Neel temperatures TN ≈ 93 K (Sm) and 84 K (Eu). Nevertheless, different relative cooling powers (RCP) of 112.6 J/kg (Sm) and 95.5 J/kg (Eu) were observed. A detailed analysis of the temperature-dependent lattice parameters shed light on a distinct magnetocaloric effect across the magnetic transition temperature, unveiling an anisotropic thermal expansion [αV = 1.41 × 10-5 K-1 (Sm) and αV = 1.54 × 10-5 K-1 (Eu)] wherein the thermal expansion axial ratio αbSm/αbEu = 0.61 became lower with increasing temperature, which suggests that the Eu sample experiences a greater thermal expansion in the b-axis direction. At the atomic bonding level, the evidence for magnetoelastic coupling around the magnetic transition temperatures TN was found through the anomalies along the average Co/Fe-O bond distance, formal valence, octahedral distortion, as well as an anisotropic lattice expansion.

Synthesis of palladium- reduced graphene oxide nanocomposite and thermal stability investigated by synchrotron radiation

Palladium-reduced Graphene oxide nanocomposite is of interest for H2 storage and H2 sensor applications. The present work reports its synthesis by hydrothermal method and the effect of temperature to test its thermal stability. The samples underwent characterisation through in-situ X-ray diffraction at high temperatures performed by synchrotron radiation at the Photon factory in KEK, Japan at different temperatures from room temperature to 300°C to determine their particle size and crystal structure. The temperature effect causes an increase in the peak intensities and a shift towards a lower 2θ value, which shows improvement in crystallinity. The investigation of the temperature dependence of lattice parameters shows an increase in lattice spacing with temperature.

Low-temperature thermal expansion behavior of the entropy-stabilized oxide (MgCoNiCuZn)O

The coefficient of thermal expansion (CTE) of entropy-stabilized oxide (MgCoNiCuZn)O has been firstly experimentally measured and studied at low temperatures below room temperature. The temperature-dependent lattice parameters of (MgCoNiCuZn)O were determined by synchrotron X-ray diffractometry. A CTE value of α = 2.2780x10-5 K−1 at 113 K for (MgCoNiCuZn)O was calculated using a second-degree polynomial fitting. The quenched homogeneous NaCl-type (MgCoNiCuZn)O structure has the highest CTE value below 133 K among all its constituent oxides. An unquenched (MgCoNiCuZn)O was also investigated, and the homogeneity was found to affect CTE values. Finally, the anisotropic behavior of the constituent oxides and (MgCoNiCuZn)O were also compared.

Structural and magnetic properties of Y3(GaAlFe)5O12 liquid-phase epitaxy films with low ferromagnetic resonance losses.

Ultra-thin rare earth iron garnet (RIG) films with a narrow ferromagnetic resonance (FMR) line width and a low damping factor have attracted a great deal of attention for microwave and spintronic applications. In this work, 200 nm Y3(GaAlFe)5O12 garnet (GaAl-YIG) films were prepared on gadolinium gallium garnet (GGG) substrates by liquid-phase epitaxy (LPE) with low saturation magnetization. The microstructural properties, chemical composition, and magnetostatic and dynamic magnetization characteristics of the films are discussed in detail. According to the structural analysis, these films exhibit a low surface roughness of less than 0.5 nm. The GaAl-YIG films show an obvious temperature dependence of lattice parameter and strain state, and the film's parameter is perfectly matched with that of the GGG substrate at 810°C. There is a clear variation in the Pb level, which brings about a gradual enhancement of the coercivity and a diminution of the squareness ratio of magnetic hysteresis loops as the growth temperature is reduced. Slight changes in surface roughness, strain condition and content of Pb induce the FMR line width and damping factor to vary on a small scale. The line width is less than 10.17 Oe at 12 GHz and the damping factor is of the order of 10-4. All these properties demonstrate that these ultra-thin GaAl-YIG films are of benefit for the development of devices operated at lower frequencies and in lower fields.

Explicit temperature coupling in phase-field crystal models of solidification

We present a phase-field crystal model for solidification that accounts for thermal transport and a temperature-dependent lattice parameter. Elasticity effects are characterized through the continuous elastic field computed from the microscopic density field. We showcase the model capabilities via selected numerical investigations which focus on the prototypical growth of two-dimensional crystals from the melt, resulting in faceted shapes and dendrites. This work sets the grounds for a comprehensive mesoscale model of solidification including thermal expansion.

Magnetic structure, magneto-caloric properties and magnetic critical behaviours of LaMn2Ge2 compounds

The structural and magnetic properties of LaMn2Ge2 compound in both the as-cast bulk and melt-spun ribbon forms have been investigated by a comprehensive set of x-ray/neutron powder diffraction, magnetic and heat capacity measurements as well as corresponding sets of data analyses. Our neutron diffraction study reveals that with decreasing temperature the magnetic state of bulk LaMn2Ge2 changes first from paramagnetic to incommensurate antiferromagnetism AFfs at TN ~ 430 K, and then gives way to incommensurate canted ferromagnetism Fmi below TC ∼ 320 K. No noticeable magnetoelastic effect was detected in the temperature dependence of lattice parameters derived from the refinement of the neutron diffraction patterns over the temperature range ~ 5–460 K. Detailed analyses of the magnetic data indicate that the magnetic phase transition around the ferromagnetic transition (TC ∼ 320 K) is second order. Under field changes of 2 T and 5 T, the maximum values of magnetic entropy change around the ferromagnetic transition respectively reach -ΔSmax = 1.65 J/kg K and -ΔSmax = 3.26 J/kg K for the bulk sample, compared with -ΔSmax = 1.21 J/kg K and -ΔSmax = 2.60 J/kg K, for the ribbon sample. The magnetic phase transition around TC has been investigated by Kouvel-Fisher analysis and the Modified Arrott Plot method with the critical exponent values indicating that the magnetic interactions in LaMn2Ge2 are long range. Moreover, it was found that the field- and temperature- magnetisation data around TC collapse onto two curves obeying the single scaling equation M(H,ε) = εβf ± (H/εβ+γ) for both the bulk and ribbon samples. With a field change of ΔB = 5 T and ΔB = 8 T, the relative cooling power for bulk sample around 320 K is derived to be RCP ~ 115 J/kg and RCP ~ 199 J/kg, respectively. These findings indicate that LaMn2Ge2 could be a promising candidate for magnetic refrigeration applications in the room temperature region.

La2Pd2In: superconductivity and lattice properties at ambient and elevated pressures

Lattice and electronic properties of La2Pd2In were studied at ambient and elevated pressures so as to determine features related to a specific atomic coordination without any influence of magnetism. We describe temperature dependences of lattice parameters, heat capacity and electrical resistivity of single-crystalline La2Pd2In (s.g. P4/mbm) in a broad temperature range 0.09–300 K. Together with the anisotropic effect of hydrostatic pressure, showing that the lattice is more compressible in the basal plane, we can conclude that the lattice is affected by degrees of freedom of the La atoms with positions not imposed by symmetry. The lattice anisotropy is smaller than that found for isostructural ferromagnet Ce2Pd2In. The equilibrium bulk modulus B 0 = (48 ± 3) GPa was determined on the basis of individual linear compressibilities. Measurement of electrical resistivity indicated a superconducting state below T = 0.59 K with a low critical field 0.005 T at T = 380 mK. The onset of superconducting state as a bulk property of La2Pd2In was confirmed by measurements of specific heat and AC magnetic susceptibility. Experimental data can be accounted by first-principles electronic-structure calculations based on density-functional theory. The measured Sommerfeld coefficient γ = 10.6 mJ mol−1 K−2, only marginally exceeding the calculated γ = 9.34 mJ mol−1 K−2, indicates only weak electronic correlations.

Structural and Magnetic Properties of Nanosized Half-Doped Rare-Earth Ho0.5Ca0.5MnO3 Manganite

We investigated the structural and magnetic properties of 20 nm-sized nanoparticles of the half-doped manganite Ho0.5Ca0.5MnO3 prepared by sol-gel approach. Neutron powder diffraction patterns show Pbnm orthorhombic symmetry for 10 K < T < 290 K, with lattice parameters a, b, and c in the relationship c/√2 < a < b, indicating a cooperative Jahn–Teller effect, i.e., orbital ordering OO, from below room temperature. In contrast with the bulk samples, in the interval 250 < T < 300 K, the fingerprint of charge ordering (CO) does not manifest itself in the temperature dependence of lattice parameters. However, there are signs of CO in the temperature dependence of magnetization. Accordingly, below 100 K superlattice magnetic Bragg reflections arise, which are consistent with an antiferromagnetic phase strictly related to the bulk Mn ordering of a charge exchange-type (CE-type), but characterized by an increased fraction of ferromagnetic couplings between manganese species themselves. Our results show that in this narrow band half-doped manganite, size reduction only modifies the balance between the Anderson superexchange and Zener double exchange interactions, without destabilizing an overall very robust antiferromagnetic state.

Measurements by x-ray diffraction of the temperature dependence of lattice parameter and crystallite size for isostatically-pressed graphite

Synthetic polygranular graphites of various grades and manufacturing routes are used in nuclear reactors for power generation, and may be used in potential fourth generation and other advanced reactor designs that will operate at higher temperature. Attention is given in this paper to isostatically-moulded synthetic polygranular graphites with porosities in the range 8% to 18%. The lattice parameters a and c for the hexagonal graphite have been measured over the temperature range from room temperature to 800°C by x-ray diffraction. The variation with temperature of the crystal lattice parameters, coherence length (crystallite size) and microstrain are discussed with reference to the microstructure and the relative strength of the bonds in-plane and normal to the graphene layers.

Heat Capacity and Thermal Expansion of M-EuTaO4

This paper presents temperature dependences of lattice parameters in the range 298–1273 K and molar heat capacity in the range 315–1335 K for high-temperature M-EuTaO4 ceramic, which has been characterized by X-ray diffraction, scanning electron microscopy, and chemical analysis.

Сравнение спектров поглощения ионов Nd-=SUP=-3+-=/SUP=- в кристаллах NdFe-=SUB=-3-=/SUB=-(BO-=SUB=-3-=/SUB=-)-=SUB=-4-=/SUB=-, Nd-=SUB=-0.5-=/SUB=-Gd-=SUB=-0.5-=/SUB=-Fe-=SUB=-3-=/SUB=-(BO-=SUB=-3-=/SUB=-)-=SUB=-4-=/SUB=- и Ho-=SUB=-0.75-=/SUB=-Nd-=SUB=-0.25-=/SUB=-Fe-=SUB=-3-=/SUB=-(BO-=SUB=-3-=/SUB=-)-=SUB=-4-=/SUB=-

Polarized optical absorption spectra in the range of some f-f transitions of Nd3+ ions in Ho0.75Nd0.25Fe3(BO3)4, Nd0.5Gd0.5Fe3(BO3)4 and NdFe3(BO3)4 crystals were compared at 90 K. Spectral features related to difference of local environment of Nd3+ ions in the mentioned crystals were revealed. In the range of 4I9/2 → 4G5/2 + 2G7/2 transition of Nd3+ ions in Ho0.75Nd0.25Fe3(BO3)4 crystal the appearance of some absorption lines owing to the change of the local symmetry during structural transition R32 → P3121 at ~ 200 K was revealed. Their intensity increases smoothly, when the temperature decreases from the transition point. Temperature dependences of lattice parameters of Ho0.75Nd0.25Fe3(BO3)4 crystal were measured. It was found that at the transition temperature there is a discontinuous change of the lattice parameter a, which indicates a phase transition of the first order. Lattice parameter c changes smoothly.

Ferromagnetic resonance in nanotwinned Ni–Mn–Ga film undergoing martensitic transformation

The ferromagnetic resonance (FMR) in the shape memory alloys (SMAs) exhibiting structural cubic-tetragonal phase transition has been studied. The influence of instability and spatial inhomogeneity of crystal lattice on the FMR spectra of twinned ferromagnetic SMAs films has been analyzed using statistical model of ferromagnetic martensite. It has been shown that the abnormally strong temperature dependence of lattice parameters of martensitic film gives a noticeable contribution to the temperature dependence of the resonance value of external magnetic field. The narrowing of the resonance peak, which had been experimentally observed on cooling of the film slightly below the Curie temperature, has been explained. It is argued that the martensitic films are good candidates for the experimental study of local elastic strains influence on the shape of the FMR peak.

Determination of temperature dependence of lattice parameters at three successive phase transitions m3m-4mm-mm2-3m

The temperature dependence of lattice parameters at three structural phase transition was determined from the condition of paraelectric phase macrosymmetry conservation in a polydomain crystal. Three analytical solutions for a second order phase transition are obtained. The analysis of the functions was made on the sample in BaTiO3. It is shown that one solution corresponds to the tetragonal and rhombohedral phases, the second one corresponds to orthorhombic phase, and the third solution is not realized.

Magnetic and transport behaviors of non-centrosymmetric Nd7Ni2Pd

Crystallographic, magnetic, electrical transport and thermodynamic properties of pseudo-binary Nd7Ni2Pd compound have been studied using temperature-dependent x-ray powder diffraction and physical property measurements. Compared to the ferromagnetic parent Nd7Pd3, the ground state of Nd7Ni2Pd is antiferromagnetic, and it exhibits strong metamagnetism. The measurements indicate two antiferromagnetic transitions in fields less than 8 kOe: a second-order paramagnetic to antiferromagnetic at TN2 = 29 K and a weak first-order antiferromagnetic to antiferromagnetic transition at TN1 = 24.5 K. The compound becomes ferromagnetic in fields of 8 kOe and higher with TC = 30 K. Temperature dependence of lattice parameters is anomalous, most prominently in the basal plane at ∼30 K; however, there is no detectable structural distortion or clear volume discontinuity around 25 K, suggesting a significant weakening of the first-order transition when compared to the binary Nd7Pd3.

Investigation of new magnetoelastic and magnetic transitions accompanied with magnetoelectric coupling in multiferroic

A new multiferroic solid solution has been developed and characterized for structure, phase transition, magnetoelectric and magnetoelastic coupling. Temperature dependent measurement of dc-magnetization on ceramic shows two magnetic transitions one around 42 K and the second at 130 K. The real part of dielectric permittivity exhibits step like change at the magnetic anomaly temperature (130 K) which indicates the presence of magnetoelectric coupling. The change in the value of dielectric permittivity on the application of magnetic field confirms the presence of magnetoelectric coupling in ceramic. The room temperature polarization (P)-electric field (E) hysteresis loop measurement shows week ferroelectric nature of sample while the magnetization (M) versus magnetic field (H) measurement suggest weakly ferromagnetic character. The ferroelectric nature of sample was further confirmed by calculating remanent polarization using PUND measurement. The Rietveld structural analysis of low temperature x-ray powder diffraction data does not reveal any crystallographic phase transition in terms of peak splitting or new reflections. However, temperature dependence of lattice parameters, tetragonality, unit cell volume, octahedral tilt angle (), bond length and bond angles reveal discontinuous changes at both the magnetic transitions observed in temperature dependence of magnetization. This confirms that both the magnetic anomalies (around 42 K and 130 K) exhibit magnetoelastic coupling accompanied with isostructural transitions.

A phase-field model for hydride formation in polycrystalline metals: Application to δ-hydride in zirconium alloys

We report a phase-field model for simulating metal hydride formation involving large volume expansion in single- and polycrystals. As an example, we consider δ-hydride formation in α-zirconium (Zr), which involves both displacive crystallographic structural change and hydrogen diffusion process. Thermodynamic Gibbs energy functions are extracted from the available thermodynamic database based on the sublattice model for the interstitial solid solutions. Solute-grain boundary interactions and inhomogeneous elasticity of polycrystals are taken into consideration within the context of diffuse-interface description. The stress-free transformation strains of multiple variants for hcp-Zr (α) to fcc-hydride (δ) transformation are derived based on the well-established orientation relationship between the α and δ phases as well as the corresponding temperature-dependent lattice parameters. In particular, to account for the large volume expansion, we introduced the mixed interfacial coherency concept between those phases—basal planes are coherent and prismatic planes are semi-coherent in computing the strain energy contribution to the thermodynamics. We analyzed the morphological characteristics of hydrides involving multiple structural variants and their interactions with grain boundaries. Moreover, our simulation study allows for the exploration of the possible hydride re-orientation mechanisms when precipitating under applied tensile load, taking into account the variation in the interfacial coherency between hydrides and matrix, their elastic interactions with the applied stress, as well as their morphology-dependent interactions with grain boundaries. The phase-field model presented here is generally applicable to hydride formation in any binary metal–hydrogen systems.

Thermal expansion of energetic material TEX obtained from x-ray diffraction and first principles calculations

X-ray powder diffraction studies on the secondary explosive TEX (C6H6N4O8) in the temperature range 25–150 °C are reported. TEX has a triclinic structure (a = 6.850 Å, b = 7.665 Å, c = 8.826 Å, α = 82.38°, β = 75.0°, and γ = 79.30° at 25 °C), space group P1¯. The crystal structure remains triclinic in this temperature range. From the temperature dependence of lattice parameters we find that thermal expansion is different along different directions. The volume thermal expansion coefficient 17.4 × 10−5 K-1 is comparable to that of a related material, CL-20. Thermal expansion along the c-direction αc is 2.2 times αa and 3 times αb. Phonon frequencies of TEX crystal at different pressures are obtained from density functional theory (DFT) calculations using CASTEP codes. The volume thermal expansion coefficient calculated using Gruneisen formalism is 6.1 × 10−5 K-1. This is the first report on the experimental determination of thermal expansion of TEX, and computation by Gruneisen formalism using DFT.

Annealing Behavior with Thickness Hindered Nucleation in Small-Molecule Organic Semiconductor Thin Films

We introduce a comprehensive overview of spontaneous and thermal induced structure changes in thin films of the high performance small-molecular organic semiconductor 5,11-bis(triethyl silylethynyl) anthradithiophene (TES-ADT). Most importantly, we find that nucleation of the TES-ADT high temperature beta phase can be induced only for films thicker than a critical thickness, while it is hindered for thinner films. The described limited crystal phase nucleation, the circumstances of which are unique in the realm of small-molecule organic semiconductors, is explained in terms of a two step nucleation mechanism while taking into account the anisotropic surface energy of crystal grains. Furthermore, we identify changes in the optical absorption spectra observed during aging of as deposited films with a spontaneous transformation from the amorphous phase to the alpha(2) phase via the alpha(1) phase of TES-ADT. The transformation takes place on the time scale of several days. Finally, we determine temperature dependence of lattice parameters of the alpha(1) and alpha(2) phases and the lattice parameters of the beta phase. Thermal expansion of the alpha(1) phase is found to be much lower than that of the alpha(2) phase.

Thermal expansion of magnetron sputtered TiCxN1-x coatings studied by high-temperature X-ray diffraction

The coefficient of thermal expansion (CTE) of TiCxN1-x can be adjusted by changing the value x between 0 (i.e. pure TiN) and 1 (pure TiC), which makes this material exceptionally useful as base layer to adapt the mismatch between the CTEs of substrate and coating. However, no comprehensive data on the CTE of sputtered TiCxN1-x has been reported up to now. Thus, in this work eleven coatings with compositions ranging from pure TiN to pure TiC were deposited using non-reactive magnetron sputtering. The elemental and phase composition were obtained by elastic recoil detection analysis and Raman spectroscopy, respectively. Powders of the coating material were analyzed using high-temperature X-ray diffraction between room temperature and up to 1000 °C to determine the temperature dependent lattice parameters. Subsequently, these lattice parameters were fitted using second order polynomials with coefficients linearly depending on the carbon content. Thus, a formula for the CTE of TiCxN1-x valid between 25 and 1000 °C was deduced which showed that at room temperature TiN has the highest CTE of 8.12 × 10−6 K−1. The CTE gradually decreases with increasing carbon content to 7.55 × 10−6 K−1 for pure TiC. While the value for TiC only shows a small increase with temperature, the CTE of TiN increases strongly up to 11.1 × 10−6 K−1 at 1000 °C. The presented formula for the temperature dependent CTE of sputtered TiCxN1-x coatings allows to calculate the required composition for TiCxN1-x base layers, in order to tune their thermal expansion for the use in complex multilayered coatings.

Influence of partial substitution of Cu atoms by Zn and Cd atoms on polymorphic transformation in the Cu1.75Te crystal

The [Formula: see text], [Formula: see text] and [Formula: see text] compounds have been synthesized and low-temperature modification single crystals obtained from the high temperature modification by polymorphic transformation. The method of high temperature X-ray diffractometer has been used to study [Formula: see text] (x = 0.05 Zn and Cd) layered single crystal. It was established that such a substitution has a significant impact on the number and temperature of polymorphic transformations. Crystallgraphic parameters were determined for each phase. Temperature dependence of lattice parameters were obtained and determined change mechanism of lattice parameters by influence of temperature.