Showing papers in "Phase Transitions in 2018"
TL;DR: The structural transformation of cesium lead iodine (CsPbI3) has been investigated in diamond anvil cells up to ∼15 GPa at room temperature by employing synchrotron radiation X-ray diffraction and Raman spectroscopy as mentioned in this paper.
Abstract: The structural transformation of cesium lead iodine (CsPbI3) has been investigated in diamond anvil cells up to ∼15 GPa at room temperature by employing synchrotron radiation X-ray diffraction and Raman spectroscopy. One reversible transformation from orthorhombic (Pnma) to monoclinic (P21/m) phase has been observed at 3.9 GPa. Isothermal pressure–volume relationship of orthorhombic CsPbI3 is well fitted by the third-order Birch–Murnaghan equation of state with K0 = 14(3) GPa, K′0 = 6(2) and V0 = 891(7) A3. The ultralow value of bulk modulus K0 demonstrates the high compressible nature of CsPbI3, similar to those of organic–inorganic metal halide perovskites. The present results provide essential information on the intrinsic properties and stability of CsPbI3, which may be applied in photovoltaic devices.
55 citations
TL;DR: Differential scanning calorimetry (DSC) analysis is a standard thermal analysis technique used to determine the phase transition temperature, enthalpy, heat of fusion, specific heat and activation as discussed by the authors.
Abstract: Differential scanning calorimetry (DSC) analysis is a standard thermal analysis technique used to determine the phase transition temperature, enthalpy, heat of fusion, specific heat and activation ...
41 citations
TL;DR: In this paper, the melting and solidification characteristics of NPCM were investigated using paraffin as the PCM and high conductive MWCNT as the nanomaterial without using any dispersant.
Abstract: The present research work aimed to investigate the melting and solidification characteristics of NPCM. The NPCM was prepared using paraffin as the PCM and high conductive MWCNT as the nanomaterial without using any dispersant. The NPCM was prepared by dispersing MWCNTs with volume fractions of 0.3%, 0.6% and 0.9% in PCM as the base PCM. SEM morphology showed the uniform dispersion of MWCNTs in the paraffin wax. The MWCNT nano-additives PCMs showed two peaks in the heating curve by DSC measurement. Lessening in melting and solidification time of 30% and 43% was attained in the case of NPCM with 0.3% and 0.9%, respectively. It is observed from the DSC analysis that the latent heat of pure paraffin during freezing and melting cycle was 139.2 J/g (at 56.61 °C) and 131.8 J/g (at 57.55 °C), respectively. Whereas, the latent heat of NPCM with 0.9% of nanofluid was 150.7 J/g (at 56.36 °C) and 148.3 J/g (58.35 °C). It is construed that a maximum change in latent heat of 7.6% and 11% was observed between pu...
31 citations
TL;DR: In this article, a non-Debye model was proposed to describe the dielectric relaxation in the [N(CH3)3H]2ZnCl4 hybrid compound.
Abstract: [N(CH3)3H]2ZnCl4 has been analyzed by X-ray powder diffraction patterns, differential scanning calorimetry and impedance spectroscopy. The [N(CH3)3H]2ZnCl4 hybrid compound is obtained by slow evaporation at room temperature and found to crystallize in the orthorhombic system with Pnma space group. Five-phase transitions at low temperature were detected by differential scanning calorimetry measurements. The analysis of Nyquist plots has revealed the contribution of three electrically active regions corresponding to the bulk mechanism, distribution of grain boundaries and electrode processes. The dielectric relaxation is described by a non-Debye model. The study of the dielectric constants ϵ′, ϵ″ and loss tangent tan (δ) with frequency exhibits a distribution of relaxation times. The complex modulus plots have confirmed the presence of grains and grain boundaries as well as a non-Debye type of relaxation in the material. Thermodynamic parameters such as the free energy for dipole relaxation ΔF, the enthalpy...
28 citations
TL;DR: In this paper, LiScSi compound with MgAgAs phase was investigated via the plane-wave pseudo-potential technique in density functional theory (DFT) and the calculated to
Abstract: In this study, several physical properties of LiScSi compound with MgAgAs phase were investigated via the plane-wave pseudo-potential technique in density functional theory (DFT) The calculated to
28 citations
TL;DR: In this article, the geometries, electrical characters and reaction paths from Fe(CO)5 molecule to small Fe clusters were investigated by using all-electron density functional theory.
Abstract: The geometries, electrical characters and reaction paths from Fe(CO)5 molecule to small Fe clusters were investigated by using all-electron density functional theory. The results show that in the d...
21 citations
TL;DR: Physical properties and phase sequence of (S)-4′-(1-methylheptyloxycarbonyl)biphenyl-4-yl 4-[7-(2,2,3, 3, 4,4, 4-4]-heptafluorobutoxy) heptyl-1-oxy]-2-fluorobenzoate exhibiting the liquid crystalline properties as mentioned in this paper.
Abstract: Physical properties and the phase sequence of (S)-4′-(1-methylheptyloxycarbonyl)biphenyl-4-yl 4-[7-(2,2,3,3,4,4,4-heptafluorobutoxy) heptyl-1-oxy]-2-fluorobenzoate exhibiting the liquid crystalline...
19 citations
TL;DR: In this article, the effect of Fe-doping at Mn-site on the structural and electrical properties of Nd0.67Ba0.33Mn1−xFexO3 perovskites has been investigated.
Abstract: The effect of Fe-doping at Mn-site on the structural and electrical properties of Nd0.67Ba0.33Mn1−xFexO3 (0 ≤ x ≤ 0.05) perovskites has been investigated. X-ray diffraction patterns show that the structural parameters change slightly due to the fact that the Fe3+ ions replacing the Mn3+ have similar ionic radius. The electrical properties of these samples have been investigated using complex impedance spectroscopy technique. a function of the frequency at different temperatures. When increasing the Fe-content, a decrease of dc conductivity was observed throughout the whole explored temperature range and the deduced activation energy values are found to increase from 128 meV for x = 0 to 166 meV for x = 0.05. The curves of the imaginary part of impedance (Z″) show the presence of relaxation phenomenon in our samples. The complex impedance spectra show semicircle arcs at different temperatures and an equivalent circuit of the type of Rg + (Rgb//Cgb) has been proposed to explain the impedance results.
19 citations
TL;DR: In this article, the structural and optical change in the In2Se3 thin films prepared by the thermal evaporation method, deposited on a glass substrate and annealed at 250°C was studied.
Abstract: In the present report, we have studied the structural and optical change in the In2Se3 thin films prepared by the thermal evaporation method, deposited on a glass substrate and annealed at 250°C. B...
17 citations
TL;DR: In this paper, the dielectric studies of diisopropylammonium chloride (DIPAC) nanoparticles embedded into opal and MCM-41 silica matrices are presented.
Abstract: The dielectric studies of diisopropylammonium chloride (DIPAC) nanoparticles embedded into opal and MCM-41 silica matrices are presented. It is shown that the ferroelectric phase transition shifts to low temperatures and broadens for DIPAC within the opal pores compared to bulk. The thermal hysteresis of the transition increases under opal nanoconfinement. No anomalies of the permittivity relevant to the ferroelectric transition are observed for DIPAC within the MCM-41 molecular sieves likely due to formation of the amorphous phase.
16 citations
TL;DR: Using the density functional theory (DFT) method, the electronic and mechanical properties of perovskites FeBO3 (B = Ti, Mn, Cr) nanostructures were studied in the pressure range of 0 −100 GPa as discussed by the authors.
Abstract: Using the density functional theory (DFT) method, the electronic and mechanical properties of perovskites FeBO3 (B = Ti, Mn, Cr) nanostructures were studied in the pressure range of 0–100 GPa. The ...
TL;DR: In this article, the synthesis and characterization of a series of heterocyclic liquid crystal, 4-{[(thiophen-2-yl)methylidene]amino}phenyl 4-alkoxybenzoates possessing even number of carbon atoms at the al...
Abstract: The synthesis and characterization of a series of heterocyclic liquid crystal, 4-{[(thiophen-2-yl)methylidene]amino}phenyl 4-alkoxybenzoates possessing even number of carbon atoms at the al...
TL;DR: In this paper, the electrical conductivity and optical absorbance of poly(methyl methacrylate)/graphene nanoplatelet (PMMA/GNP) composite films were studied.
Abstract: Effects of graphene nanoplatelet (GNP) addition on the electrical conductivity and optical absorbance of poly(methyl methacrylate)/graphene nanoplatelet (PMMA/GNP) composite films were studied. Opt...
TL;DR: In this article, the well-known anisotropic XY spin chains in a transverse magnetic field were studied in the context of bipartite entanglement and quantum discord.
Abstract: The well-known anisotropic XY spin chains in a transverse magnetic field are studied in the context of bipartite entanglement and quantum discord. By using Jordan–Wigner transformation, the model m...
TL;DR: In this paper, a detailed analysis of anisotropy of the thermal expansion tensor is performed for β-TlInS2 crystals in the course of their phase transitions, and it is shown that the crystals aged for one year are composed from at least two polytypes, which undergo phase transitions at different temperatures.
Abstract: Basing on the thermal expansion studies performed for β-TlInS2 crystals in the course of their phase transitions, we have found that the crystals aged for one year are composed from at least two polytypes, which undergo phase transitions at different temperatures. The detailed analysis of anisotropy of the thermal expansion demonstrates that all of the diagonal components of the thermal expansion tensor associated with the eigensystem have almost the same modules but differ by their signs. This leads to appearance of an elliptical conical surface of zero thermal expansion. The orientation of this surface does not depend on the temperature in the temperature interval under study. We have also found that the thermal expansion coefficients along the crystallographic a and b axes are close to zero.
TL;DR: In this paper, a 2D layered Mn-MOF with a thiolate-bridged binuclear node similar to the active site of the [MnAu]-hydrogenase was described.
Abstract: Microscale crystals of a 2D layered Mn-MOF [Mn2(TylP)4]n (TylP=5-(1,2,4-triazol-1-yl)isophthalic) with a thiolate-bridged binuclear Mn(II) node similar to the active site of the [MnAu]-hydrogenase ...
TL;DR: In this article, the authors studied phase transitions and thermodynamic properties in the two-dimensional antiferromagnetic Ising model with next-nearest-neighbor interaction on a Kagome lattice by Monte Carlo simulations.
Abstract: We study phase transitions and thermodynamic properties in the two-dimensional antiferromagnetic Ising model with next-nearest-neighbor interaction on a Kagome lattice by Monte Carlo simulations. A histogram data analysis shows that a second-order transition occurs in the model. From the analysis of obtained data, we can assume that next-nearest-neighbor ferromagnetic interactions in two-dimensional antiferromagnetic Ising model on a Kagome lattice excite the occurrence of a second-order transition and unusual behavior of thermodynamic properties on the temperature dependence.
TL;DR: In this paper, the influence of sintering conditions on structural, thermal, dielectric and ferroelectric properties of Na0.5Bi 0.5TiO3 ceramics was investigated.
Abstract: Na0.5Bi0.5TiO3 ceramics were prepared by a conventional solid-state reaction method and by a hot-pressing route. The influence of sintering conditions on structural, thermal, dielectric and ferroelectric properties of these ceramics was investigated. All obtained samples exhibited a single perovskite phase. It was shown that the sintering conditions significantly influence the properties under investigation. This includes changes in the value of the electric permittivity ϵ and dielectric loss tanδ, a shift of Tm and Td and change of the ferroelectric properties. These effects are mainly related to volatility of the Na and Bi components during the sintering process along with formation of their compensating charge defects, which leads to local structure change.
TL;DR: In this paper, the magnetocaloric effect in La0.7Ca0.15Sr 0.15MnO3 perovskite has been studied by both direct and indirect measurement techniques.
Abstract: A systematic study of the magnetocaloric effect in La0.7Ca0.15Sr0.15MnO3 perovskite has been performed by both direct and indirect measurement techniques. In particular, the adiabatic temperature change has been measured by a purpose-built probe suitable for laboratory-scale samples, while magnetic measurements were carried out by standard magnetometric techniques. The observation of the effective behavior of the studied systems in adiabatic conditions and the significant value of the isothermal entropy variation indicate that La0.7Ca0.15Sr0.15MnO3 could be considered as a potential candidate for application in magnetic refrigeration around room temperature. Moreover, the critical exponents (γ, β and δ) determined using the Kouvel–Fisher method, the modified Arrott plot and the critical isotherm analysis are in good agreement with the theoretical prediction of the 3D-Ising model, indicating that the magnetic interactions are of short-range nature.
TL;DR: Two new binary liquid crystalline mixtures composed from the chiral liquid crystal materials with partially fluorinated non-chiral chain and without lateral substitution at the molecular core are presented in this article.
Abstract: Two new binary liquid crystalline mixtures composed from the chiral liquid crystalline materials with partially fluorinated non-chiral chain and without lateral substitution at the molecular core h...
TL;DR: In this article, amorphous samples of Sb-substituted Se78−xTe20Sn2Sbx (0, 2, 4, 6) have been prepared using melt quench technique.
Abstract: Bulk amorphous samples of Sb-substituted Se78−xTe20Sn2Sbx (0 < x < 6) have been prepared using melt quench technique. The structure of Se78−xTe20Sn2Sbx (x = 0, 2, 4, 6) glassy alloys has been inves...
TL;DR: In this paper, single crystals of Pb5Ge3O11 (PGO), pure and doped with Cr3+ ions, were grown by means of Czochralski and Kyropoulos method, respectively.
Abstract: Single crystals of Pb5Ge3O11 (PGO), pure and doped with Cr3+ ions, were grown by means of Czochralski and Kyropoulos method, respectively. Structural, microstructural, thermodynamic and dielectric ...
TL;DR: In this article, the high pressure behavior of zinc sulphide, ZnS, was investigated, using an in situ X-ray powder diffraction technique in a diamond anvil cell, at pressures and temperatures up to 35 GPa and 1000 K, respectively.
Abstract: The high-pressure behaviour of zinc sulphide, ZnS, has been investigated, using an in situ X-ray powder diffraction technique in a diamond anvil cell, at pressures and temperatures up to 35 GPa and 1000 K, respectively. The pressure-induced phase transition from a zincblende (B3) to a rocksalt (B1) structure was observed. This transition occurred at 13.4 GPa and at room temperature, and a negative dependence on temperature for this transition was confirmed. The transition boundary was determined to be P (GPa) = 14.4 − 0.0033 × T (K).
TL;DR: The low-lead (1-x)Pb(Mg1/3Nb2/3)O3-xBaTiO3 (x = 0, 0.025, 0.,075, 0, 10 and 0.15) ceramics were fabricated by a two-step solid-state reaction route.
Abstract: The low-lead (1-x)Pb(Mg1/3Nb2/3)O3-xBaTiO3 (x = 0, 0.025, 0.05, 0.075, 0.10 and 0.15) ceramics were fabricated by a two-step solid-state reaction route. The X-ray diffraction characterization confi...
TL;DR: In this article, the authors proposed the giant dipolar defects as the explanation of the colossal permittivity in co-doped rutile and showed that these defects can be found in (Nb + nb+n) + in (nb + in) rutiles.
Abstract: Searching for giant dipolar defects, suggested as the explanation of the colossal permittivity (CP) in (Nb + In) co-doped rutile, we have recently published (J. Appl. Phys. 119, 154105 (2016) and P...
TL;DR: For the first time, activated carbon materials have been used in perovskite solar cells as mentioned in this paper, where they have excellent electronic properties and low cost, and they have been shown to have potential applications in solar cells.
Abstract: Carbon materials have potential applications in perovskite solar cell because of their excellent electronic properties and low cost. In this paper, we report, for the first time, activated carbon a...
TL;DR: In this article, a phenomenological model was used to predict magnetocaloric properties of La0.6Ca0.2Sr 0.2MnO3/Sb2O3 oxides.
Abstract: In this paper, magnetocaloric properties of La0.6Ca0.2Sr0.2MnO3/Sb2O3 oxides have been investigated. The composite samples were prepared using the conventional solid-state reaction method. The second-order phase transition can be testified with the positive slope in Arrott plots. An excellent agreement has been found between the −ΔSM values estimated by Landau theory and those obtained using the classical Maxwell relation. The field dependence of the magnetic entropy change analysis shows a power law dependence,|ΔSM|≈Hn , with n(TC) = 0.65. Moreover, the scaling analysis of magnetic entropy change exhibits that ΔSM(T) curves collapse into a single universal curve, indicating that the observed paramagnetic to ferromagnetic phase transition is an authentic second-order phase transition. The maximum value of magnetic entropy change of composites is found to decrease slightly with the further increasing of Sb2O3 concentration. A phenomenological model was used to predict magnetocaloric properties of L...
TL;DR: In this paper, thin films of As40Se60 and AS40Se50Ge10 were prepared on glass substrates by thermal evaporation method with thickness 1000 nm and the prepared films were amorphous in nature.
Abstract: The thin films of As40Se60 and As40Se50Ge10 were prepared on glass substrates by thermal evaporation method with thickness 1000 nm. The prepared films were amorphous in nature which was confirmed t...
TL;DR: In this paper, the ultrasonic and elastic properties of Tl- and Hg-based cuprate superconductors were reviewed and a discontinuity in the sound velocity and elastic moduli was observed near Tc.
Abstract: This review is regarding the ultrasonic and elastic properties of Tl- and Hg-based cuprate superconductors. The objectives of this paper were to review the ultrasonic attenuation above the transition temperature Tc, and sound velocity and elastic anomalies at Tc in the Tl- and Hg-based cuprate superconductors. A discontinuity in the sound velocity and elastic moduli is observed near Tc for the Hg-based and other cuprate high temperature superconductor but not the Tl-based superconductor. Ultrasonic attenuation peaks are observed between 200 and 250 K in almost all Tl- and Hg-based cuprate superconductors reported. These peaks were attributed to lattice stepping and oxygen ordering in the Tl-O and Hg-O layers. Some Tl- and Hg-based superconductors show attenuation peak near Tc. However, this is not a common feature for the cuprate superconductors. The ultrasonic attenuation decrease rate below Tc is slower than that expected from a Bardeen-Cooper-Schrieffer (BCS) and pseudo-gapped superconductor.
TL;DR: In this paper, the Archimedes method was used for the preparation of high-density lead-free potassium-bismuth titanate K0.5Bi 0.5TiO3.
Abstract: The preparation of high-density lead-free potassium-bismuth titanate K0.5Bi0.5TiO3 about 96–98% of the calculated density (X-ray), confirmed by the Archimedes method, is presented. All stages of th...