Synthesis and study of structural,dielectric, magnetic and magnetoelectric properties of K<Subscript>0.5</Subscript>Na<Subscript>0.5</Subscript>NbO<Subscript>3</Subscript>–CoMn<Subscript>0.2</Subscript>Fe<Subscript>1.8</Subscript>O<Subscript>4</Subscript> composites

Magnetoelectric (ME) composites consisting of K_0.5Na_0.5NbO₃ (KNN) as ferroelectric phase and CoMn_0.2Fe_1.8O₄ (CMFO) as ferrite phase with general formula (x) CoMn_0.2Fe_1.8O₄–(1???x) K_0.5Na_0.5NbO₃ (x?=?10, 20, 30, 40 and 50 wt%) were synthesized using solid state reaction method. X-ray diffraction analysis asserts the existence of component phases including spinel phase of CMFO and orthorhombic phase of KNN. Field emission scanning electron microscopy has been used for studying the morphology and calculation of average grain size. The temperature dependent dielectric properties including dielectric constant (\(\varepsilon ^{\prime}\)) and dielectric loss (tan δ) at different frequencies has been studied and both are found to increase with incorporation of CMFO. Magnetic hysteresis loops have been measured at temperatures of 300 and 5 K. Variation of magnetization versus temperature has been studied in field cooled and zero field cooled modes. Polarization versus electric field (P–E) hysteresis loops are obtained at room temperature indicating presence of ferroelectric ordering in the composites at room temperature. The remnant polarization (2P_r) and coercive field (2E_c) are found to decrease linearly with incorporation of CMFO. ME voltage coefficient (α_ME) has been measured. The maximum value of α_ME is found to be 5.941 mV/cm-Oe for 10% CMFO–90% KNN bulk composite.     

Chemical,morphological, structural,optical, and magnetic properties of Zn<Subscript>1−x</Subscript>Nd<Subscript>x</Subscript>O nanoparticles

In the present investigation, we made an endeavor to fabricate the ZnO nanoparticles and achieved the tunable properties with Nd doping. The Nd-doped ZnO nanoparticles were characterized via X-ray diffraction (XRD), Raman, and X-ray photoelectron spectroscopy (XPS) studies that confirmed the successful doping of Nd ions in the ZnO crystal lattice without amending its hexagonal phase. The particle morphology revealed nearly spherical particles with uniform size distribution. The band gap of these samples was determined using diffuse-reflectance spectra (DRS) and was found to vary from 3.17 to 3.21 eV with increasing Nd concentration. A broad and intense emission band at 1083 nm for Nd doped ZnO nanoparticles is observed and is assigned to corresponding emission transition ⁴F_3/2?→?⁴I_11/2 of Nd³⁺ ions. Furthermore, the magnetic studies indicate that the Nd doping altered the magnetic behavior of nanocrystalline ZnO particles from diamagnetic to ferromagnetic at 300 K and that the magnetization of these samples decreased with increasing Nd concentration. The tunable optical band gap as well as room-temperature ferromagnetism of these samples may find applications in both optoelectronics and spintronics.     

Investigation of solid solution of ZrP<Subscript>2</Subscript>O<Subscript>7</Subscript>–Sr<Subscript>2</Subscript>P<Subscript>2</Subscript>O<Subscript>7</Subscript>

In this study, ZrP₂O₇ was synthesized by the solid state reaction of ZrO₂ and NH₄H₂PO₄ at 900 °C. Then, in set 1; 10, 5, 1, 0.5, 0.1, 0.05, 0.03% previously prepared Sr₂P₂O₇ were doped into ZrP₂O₇, and Sr₂P₂O₇ slightly affect the unit cell parameter of cubic ZrP₂O₇ (a = 8.248(6)–8.233(8) Å). The reverse of this process was also applied to Sr₂P₂O₇ system (set 2). ZrP₂O₇ changes the unit cell parameters of orthorhombic Sr₂P₂O₇ in between a = 8.909(5)–8.877(5) Å, b = 13.163(3)–13.12(1) Å, and c = 5.403(2)–5.386(4) Å. Analysis of the vibrations of the P₂O ₇ ^4? ion and approximate band assignments for IR and Raman spectra are also reported in this work. Some coincidences in infrared and Raman spectra both sets were found and strong P–O–P bands were observed. Surface morphology, EDX analysis, and thermoluminescence properties of both sets were given the first time in this paper.     

Preparation,characterization, conductivity and thermal expansion studies of Ca<Subscript>0.5</Subscript>SbMP<Subscript>3</Subscript>O<Subscript>12</Subscript> (M = Al,Fe, Cr)

Nasicon type compounds of general formula Ca_0.5SbMP₃O₁₂ (M = Al, Fe, Cr) are prepared by solid-state method. All the compounds crystallize in hexagonal lattice with space group. The IR spectra show characteristic PO₄ vibrations. Conductivity studies indicate the presence of charged defects. The Cole-Cole plots of impedance are semicircles between 150 and 350 °C. The thermal expansion of these samples is studied in the temperature range 25–500 °C.     

Micro-structural,dielectric, ferroelectric and piezoelectric properties of mechanically processed (Pb<Subscript>1−x</Subscript>La<Subscript>x</Subscript>)(Zr<Subscript>0.60</Subscript>Ti<Subscript>0.40</Subscript>)O<Subscript>3</Subscript> ceramics

In this work, (Pb_1?xLa_x)(Zr_0.60Ti_0.40)O₃ (PLZT x/60/40, x?=?at.%) ceramics were prepared by using high energy mechanical ball milling followed by cold isostatic pressing (CIP), investigated for their micro-structural, dielectirc, ferroelectric and piezoelectric properties. Mechanical activation results in the highly reactive nature of the nano size milled PLZT powders, which enables the partial perovskite phase formation, confirmed by room temperature XRD patterns. CIP leads to a higher density with a closely packed dense microstructure of sintered PLZT ceramics shown in SEM images. The grain size of PLZT x/60/40 ceramics was found to be decreasing with increasing La³⁺ content. The highest relative density of ~?97% was found to be for PLZT 8/60/40 ceramics with grain size of ~?1.35 µm. The PLZT 8/60/40 system also shows the highest dielectric constant of ~?1976, remnant polarization of 29.1 µC/cm², piezoelectric coefficients (d₃₃?\(~ \cong ~\)?570 pC/N, g₃₃?\(~ \cong ~\)?28.03?×?10^?3 Vm/N) and electromechanical coupling factors (k_p?=?k₃₃?=?64.1% and k₃₁?=?54%). The elastic compliances for the PLZT x/60/40 ceramics were also obtained.     

Chemical interaction of InAs,InSb, GaAs,and GaSb with (NH<Subscript>4</Subscript>)<Subscript>2</Subscript>Cr<Subscript>2</Subscript>O<Subscript>7</Subscript>–HBr–C<Subscript>4</Subscript>H<Subscript>6</Subscript>O<Subscript>6</Subscript> etching solutions

This paper presents results on the kinetics and mechanism of the physicochemical interaction of InAs, InSb, GaAs, and GaSb semiconductor surfaces with (NH₄)₂Cr₂O₇–HBr–C₄H₆O₆ etching solutions under reproducible hydrodynamic conditions in the case of laminar etchant flow over a substrate. We have identified regions of polishing and nonpolishing solutions and evaluated the apparent activation energy of the process. The surface morphology of the crystals has been examined by microstructural analysis after chemical etching. The results demonstrate that the presence of C₄H₆O₆ in etchants helps to reduce the overall reaction rate and extend the region of polishing solutions.     

Temporal Stability of Magnetization of ε-In<Subscript>0.24</Subscript>Fe<Subscript>1.76</Subscript>O<Subscript>3</Subscript> Nanoparticles

The kinetics of spontaneous demagnetization in nanoparticles of the exotic epsilon-phase of indium-doped iron(III) oxide (ε-In_0.24Fe_1.76O₃) has been studied using the method of accelerated testing of magnets for temporal stability in a magnetization-reversal field. Time dependences of the magnetization of nanoparticles measured in a wide range of magnetic fields exhibited rectification in semilogarithmic coordinates. The dependence of the magnetic viscosity on the magnetic field has been measured and used for determining the fluctuation field and activation volume. A relationship between the magnetic viscosity and magnetic noise caused by random thermoinduced magnetization reversal in separate nanoparticles is established.     

Synthesis and properties of Ca<Subscript>2.8</Subscript>Ln<Subscript>0.2</Subscript>Co<Subscript>4</Subscript>O<Subscript>9 + δ</Subscript> (Ln = La,Nd, Sm,Tb-Er) solid solutions

Ca_2.8Ln_0.2Co₄O_{9 + δ} (Ln = La, Nd, Sm, Tb-Er) solid solutions have been prepared via a citrate route and their structural parameters have been determined. Their thermal expansion, thermoelectric power, thermal conductivity, and electrical conductivity have been measured above room temperature. The results demonstrate that all of the materials obtained are p-type semiconductors. Their unit-cell parameters decrease with a decrease in the ionic radius of the Ln³⁺ cation substituted for Ca²⁺, and their thermoelectric power increases with an increase in the number of f electrons of the Ln³⁺ cation. We have determined the electron and phonon contributions to the thermal conductivity of the materials and evaluated the thermoelectric power factor and thermoelectric figure of merit of the oxide ceramics. The highest thermoelectric power factors are offered by the Ca_2.8Tb_0.2Co₄O_{9 + δ} and Ca_2.8Er_0.2Co₄O_{9 + δ} solid solutions: 0.27 and 0.29 mW/(m K²), respectively, at T = 1100 K.     

Crystal growth,X-ray diffraction characterization,and Mössbauer spectroscopy of FeIn<Subscript>2</Subscript>S<Subscript>4</Subscript>-In<Subscript>2</Subscript>S<Subscript>3</Subscript> solid solutions

Crystals of (FeIn₂S₄)_{1 ? x} (In₂S₃) _x solid solutions consisting of large blocks have been grown by directional solidification (horizontal Bridgman process). FeIn₂S₄, In₂S₃, and the solid solutions are shown to crystallize in the spinel structure. The composition dependence of their unit-cell parameter a follows Vegard's law. The local states of the Fe ions in the solid solutions have been studied by Mössbauer spectroscopy in a transmission geometry.     

Effect of refractory nitride nanoadditives on the properties of (Bi,Pb)<Subscript>2</Subscript>Sr<Subscript>2</Subscript>Ca<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>10+δ</Subscript>

We have investigated the interaction between (Bi,Pb)₂Sr₂Ca₂Cu₃O_10+δ (Bi-2223) and small additions (0.05–0.3 wt %) of nitride powders (TaN, AlN, HfN, NbN, Si₃N₄, TiN, and ZrN) with a particle size from 0.02 to above 0.5 μm and the effect of these nitrides on the microstructure, phase composition, distribution, and morphology of the resulting second-phase inclusions. The concentration and particle size of the nitrides and sintering conditions are shown to influence the superconducting transition temperature T _c, critical current density j _c, irreversible remanent magnetization, bulk density, and mechanical properties of the Bi-2223/nitride composites.     

Structural,magnetic and magnetocaloric investigation of La<Subscript>0.67</Subscript>Ba<Subscript>0.33</Subscript>Mn<Subscript>1−x</Subscript>Ni<Subscript>x</Subscript>O<Subscript>3</Subscript> (x = 0, 0.025 and 0.075) manganite

In this paper, we report the structural, magnetic and magnetocaloric properties of Ni-doped La_0.67Ba_0.33Mn_1?xNi_xO₃ (x?=?0, 0.025 and 0.075) manganites. Our compounds were synthesized using the sol–gel method. The structural analysis using Rietveld refinement shows that Ni-doped LaBaMnO₃ system crystallizes in the rhombohedral symmetry with \({\text{R}}\bar {3}{\text{c}}\) space group. Magnetization measurements versus temperature in a magnetic applied field of 0.05 T reveal that all the compositions exhibit a transition from a ferromagnetic to paramagnetic phase with increasing temperature. A systematic decrease in the transition temperature is clearly observed upon Ni doping and a near room temperature T_C (302 K) is achieved with x?=?0.075 composition. The maximum magnetic entropy change \(\left( { - ~\Delta {\text{S}}_{{\text{M}}}^{{\hbox{max} }}} \right)\) in a magnetic field change of 5 T is found to be 2.12, 2.78 and 1.78 J/kg K for x?=?0, 0.025 and 0.075, respectively. At this value of magnetic field, large relative cooling power values are obtained in our samples, especially for x?=?0.075 (271 J/kg) making it a promising candidate for magnetic refrigeration near room temperature.     

Chemical interaction of InAs,InSb, GaAs,and GaSb crystals with aqueous (NH<Subscript>4</Subscript>)<Subscript>2</Subscript>Cr<Subscript>2</Subscript>O<Subscript>7</Subscript>–HBr solutions

We have studied the nature and kinetics of the chemical interaction of InAs, InSb, GaAs, and GaSb crystals with aqueous (NH₄)₂Cr₂O₇–HBr solutions. The dissolution rate of the crystals has been measured as a function of etchant composition, solution stirring rate, and temperature. The results demonstrate that the dissolution rate of the semiconductors is diffusion-limited. We have determined the composition ranges of polishing solutions, optimized their compositions, and found conditions for the dynamic chemical polishing of the semiconductors. Ultrasmooth polished semiconductor surfaces have been obtained, with R _a ≈ 1 nm.     

Modelling,structural, thermal,optical and vibrational studies of a new organic–inorganic hybrid material (C<Subscript>5</Subscript>H<Subscript>16</Subscript>N<Subscript>2</Subscript>)Cd<Subscript>1.5</Subscript>Cl<Subscript>5</Subscript>

Chemical preparation, theoretical calculations, X-ray single-crystal diffraction, thermal analysis, electrochemical measurements, IR, Raman and UV spectroscopic investigations of a novel organic–inorganic hybrid material (C₅H₁₆N₂)Cd_1.5Cl₅ are described. The structure provides a new interesting example of infinite inorganic chains of [Cd_1.5Cl₅]\(_{\mathbf {n}}^{\boldsymbol {2\mathrm {n}-}}\) following the a crystallographic direction. The [Cd_1.5Cl₅]^2? anions are interconnected by N–H ? Cl hydrogen bonds. The Hirshfeld surface and associated fingerprint plots of the compound are presented to explore the nature of intermolecular interactions and their relative contributions in building the solid-state architecture. IR and Raman spectra are reported and discussed on the basis of group theoretical analysis and quantum chemical density functional theory (DFT) calculation. The molecular HOMO–LUMO compositions and their respective energy gaps are also drawn to explain the activity of our compound. Thermal analysis reveals the anhydrous character of the compound.     

Synthesis and Structure of Mixed Cromate–Nitrate Complexes of Hexavalent Actinides, [(CH<Subscript>3</Subscript>)<Subscript>4</Subscript>N][(AnO<Subscript>2</Subscript>)(CrO<Subscript>4</Subscript>)(NO<Subscript>3</Subscript>)] (An = U,Np, Pu)

Mixed-anion compounds of the general composition [(CH₃)₄N][(AnO₂)(CrO₄)(NO₃)], where An = U, Np, and Pu, were synthesized and structurally characterized. The structural motif of these compounds is based on anionic ribbons of the composition [AnO₂(NO₃)(CrO₄)]_n^n–, consisting of seven-vertex An polyhedra linked via oppositely oriented CrO₄ tetrahedra and NO₃ groups acting in the An polyhedra as terminal bidentate ligands. Every four anionic ribbons form channels oriented along b-axis. Tetramethylammonium cations linked with the O atoms of the ribbons by hydrogen bonds are located in these channels. Actinide contraction is observed in the series U–Np–Pu. It is manifested in a regular decrease in the interatomic distances in the An polyhedra, in parameters b and c, and in the unit cell volume.     

Synthesis,charge transport studies,and microwave shielding behavior of nanocomposites of polyaniline with Ti-doped γ-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>

This article reports the synthesis, charge transport studies, and microwave shielding properties of polyaniline–Ti-doped γ-Fe₂O₃ nanocomposite. The composite has been prepared by the in situ chemical oxidative polymerization using dodecylbenzenzesulfonic acid as a dopant. These resulting polymer composites have been found thermally stability up to 260 °C with magnetization value of ~10 emu/g. The temperature dependence of electrical conductivity reveals the applicability of Mott’s 3D-VRH model. The composites has shown the shielding effectiveness of 35.64–45.20 dB (>99.99% attenuation) in 12.4–18 GHz (Ku-Band) frequency range. The enhancement of SE has been due to combination of dielectric and magnetic losses leading to decrease in skin depth increase in total (σ_T) conductivity and better matching of input impedance.     

Y<Subscript>3−x</Subscript>Gd<Subscript>x</Subscript>Fe<Subscript>5</Subscript>O<Subscript>12</Subscript>: controlled synthesis,characterization and investigation of its magnetic properties

Gadolinium substituted yttrium iron garnet (Gd: YIG: Y_3?xGd_xFe₅O₁₂ where x?=?0, 0.25, 0.5, 0.75, 1, 1.25, 1.5) nanopowders were synthesized by microwave hydrothermal method. Phase structure of synthesized powders was examined using fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) which revealed a cubic garnet structure. Spherical-like morphology of synthesized powders was confirmed by field emission scanning electron microscopy (FESEM) studies. The synthesized powders were sintered at 1100?°C for 60 min using microwave furnace and characterized by using XRD and FESEM. Magnetic properties such as saturation magnetization and Curie temperature were measured using vibration sample magnetometer (VSM) and differential scanning calorimetry (DSC) studies respectively. Temperature stability of magnetization was measured using pulse magnetometer and complex permeability was measured over a frequency range of 100 kHz–1.8 GHz. The obtained results showed that the saturation magnetization as well as permeability decrease while curie temperature and temperature stability increase with Gd concentration. It is concluded that substitution of Gd makes the YIG better microwave magnetic material, which may be used in high power non-reciprocal microwave devices in the microwave region.     

First-principles calculations of crystal structure,electronic structure and optical properties of Ba<Subscript>2</Subscript>RETaO<Subscript>6</Subscript> (RE = Y,La, Pr,Sm, Gd)

The crystal structure, electronic structure and optical properties of Ba₂RETaO₆ (RE?=?Y, La, Pr, Sm, Gd) have been studied by first-principles calculation. The calculated lattice parameters are in good agreement with the previously reported values. With increasing the atomic number of RE (i.e., the number of 4f electrons), the energy level of RE 4f bands becomes lower continuously. The relationship between the electronic structure and optical properties is explored based on first-principles calculation. The electron transitions between O 2p states, RE 4f states and Ta 5d states have a key effect on optical properties such as dielectric function, refractive index, absorption coefficient and reflectivity. The phase structures have great influence on the optical properties of Ba₂SmTaO₆ and Ba₂GdTaO₆, and the big variation of reflectivity induced from phase transition makes them have potential applications in the infrared radiation protection area.     

Extraction,detection, and profiling of serum biomarkers using designed Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@SiO<Subscript>2</Subscript>@HA core–shell particles

Serum biomarkers in the form of proteins (e.g. cluster of differentiation-44 (CD44)) have been demonstrated to have high clinical sensitivity and specificity for disease diagnosis and prognosis. Owing to the high sample complexity and low molecular abundance in serum, the detection and profiling of biomarkers rely on efficient extraction by materials and devices, mostly using immunoassays via antibody-antigen recognition. Antibody-free approaches are promising and need to be developed for real-case applications in serum to address the limitations of antibody-based techniques in terms of robustness, expense, and throughput. In this work, we demonstrated a novel approach using hyaluronic acid (HA)-modified materials/devices for the extraction, detection, and profiling of serum biomarkers via ligand-protein interactions. We constructed Fe₃O₄@SiO₂@HA particles with different sizes through layer-by-layer assembly and for the first time applied HA-functionalized particles in the facile extraction and sequence identification of CD44 in serum by mass spectrometry. We also first validated HA-CD44 binding through electrochemical sensing using HA-modified electrodes in both standard solutions and diluted serum samples, achieving a detection limit of ～0.6 ng/mL and a linear response range from 1 ng/mL to 10 μg/mL. Furthermore, we performed profiling of HA-binding serum proteome, providing a new preliminary benchmark for the construction of future databases, and we investigated selected surface chemistries of particles for the capture of proteins in serum. Our work not only resulted in the development of a platform technology for CD44 extraction/detection and HA-binding proteome identification, but also guided the design of ligand affinity-based approaches for antibody-free analysis of serum biomarkers towards diagnostic applications.

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Microstructure,interfaces and creep behaviour of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–Sm<Subscript>2</Subscript>O<Subscript>3</Subscript> (ZrO<Subscript>2</Subscript>) eutectic ceramic composites

New compositions in the melt-grown eutectic ceramics field are investigated for thermomechanical applications. This paper is focused on the Al₂O₃–Sm₂O₃–(ZrO₂) system. The studied compositions give rise to interconnected microstructures without anisotropy along the growth direction. At variance with the binary eutectic Al₂O₃–SmAlO₃, the homogeneity of the microstructure of the Al₂O₃–SmAlO₃–ZrO₂ ternary eutectic is less sensitive to the growth rate. Interfaces between the alumina and perovskite phases are investigated by high-resolution transmission electron microscopy (TEM). They are semi-coherent. In stepped interfaces, the facets are parallel to dense planes of each phase. The steps have a dislocation character and may accommodate both misfits. The ternary eutectic displays a very good creep behaviour with strain rates very close to those obtained on other previously studied eutectics in the Al₂O₃–RE₂O₃(RE = Y, Gd, Er)–ZrO₂ systems. The deformation micromechanisms are analysed by TEM in the three eutectic phases. After creep, dislocations are present in every phase. The activation of unusual slip systems (pyramidal slip in the alumina phase) shows that high local stresses can be reached. The presence of dislocation networks with low energy configurations is consistent with predominance of dislocation climb processes controlled by bulk diffusion.     

Growth of bulk β-BaB<Subscript>2</Subscript>O<Subscript>4</Subscript> crystals of high optical quality in the BaB<Subscript>2</Subscript>O<Subscript>4</Subscript>-NaBaBO<Subscript>3</Subscript> system

Phase equilibria along the BaB₂O₄-NaBaBO₃ join of the BaO-B 2 O 3 -Na 2 O system are studied by differential thermal analysis and modified visual thermal analysis. The join is shown to be suitable for growing - BaB₂O₄ crystal of high optical quality.Translated from Neorganicheskie Materialy, Vol. 41, No. 1, 2005, pp. 64–69. Original Russian Text Copyright © 2005 by Kokh, Kononova, Fedorov, Bekker, Kuznetsov.