Magnetic properties and magnetoelectric effect in Ni0.8Co0.1Cu0.1Fe2O4 + PbZr0.2Ti0.8O3 composites

Composites with compositions x (Ni_0.8Co_0.1Cu_0.1Fe₂O₄) + (1−x) PbZr_0.2Ti_0.8O₃ (x-mole fraction varies as 0.15, 0.25, 0.35 and 0.45) were prepared by standard ceramic method. The presence of constituent phases, namely ferrite and the ferroelectric were confirmed by X-ray diffraction. The structural analyses were carried out using the obtained powder pattern X-ray data. The porosity of the samples was calculated and the values obtained lie between 10% to 19%. To date, the variations in the magnetic properties with variation in ferrite phase in composites and thereby its influence on magnetoelectric effect is not yet reported. The saturation magnetization (Ms) and magnetic moment (η_B) in Bohr magneton were calculated for all the composites. The static value of magnetoelectric voltage coefficient (dE/dH) was measured as a function of intensity of magnetic field. The maximum value of ME coefficient was observed for a composite with 35% ferrite + 65% ferroelectric phase.     

Microstructural change and interfacial reactions of Pt/Ti thin films on SiNx/Si during annealing in various ambients

The microstructural changes and interfacial reactions of Pt/Ti/SiN_x/Si during annealing were investigated using transmission electron microscopy (TEM), X-ray diffraction (XRD), and Auger electron spectroscopy (AES). Pt/Ti thin films were deposited on SiN_x/Si substrates by a d.c. magnetron sputtering system. Pt/Ti/SiN_x/Si specimens were annealed at 600°C in an oxygen ambient or a vacuum. Annealing ambients strongly influenced the microstructural change in the Pt/Ti thin films. When the specimens were annealed in oxygen, the oxygen diffused into metal layers from the ambient and reacted with Ti to form the rutile phase. When the specimens were annealed in vacuum, Ti reacted with nitrogen which was dissociated from SiN_x to form TiN and reacted with Pt to form Pt₃Ti.     

Transmission electron microscopy on the microstructure of 7050 aluminium alloy in the T74 condition

The microstructure of 7050 aluminium alloy in the T74 condition has been investigated by transmission electron microscopy. It was found that the alloy contains the superlattice Al₃Zr phase, η′ phase and Al₇Cu₂Fe constituent phase. The η′ phase is proposed to have an orthorhombic crystal structure witha=0.492 nm,b=0.852 nm andc=0.701 nm. The orientation relationship between the matrix and η′ phase is [11−2]_m//[100]_η′; [1−]_m//[010]_η′;[−1−1−1]_m//[001]_η′. The phases on the small-angle grain boundary are found to be mainly η′ phase and Cu/Si-rich phase, whereas on the large-angle grain boundary there is only η phase.     

Properties of Va metal-B films prepared by r.f.-sputtering

Nb_100−x B _x alloy films were prepared by the r.f.-sputtering method in the chemical composition range of 30 ≦x ≦ 76. Nb_100−x B _x (30 ≦x ≦ 54) films consisted of the amorphous state, and NbB₂ crystal phase was observed on Nb_100−xB_x (67 ≦x ≦ 76) films. A remarkable preferred orientation with the (001) plane of NbB₂ in parallel to the film surface was observed on Nb₃₃B₆₇ film. d.c. electrical conductivity of Nb_100−xB_x (30 ≦x ≦ 76) films decreased with increasing content of boron in the range from 7.3×10³ to 7.6 ×10²Ω⁻¹cm⁻¹. Micro-Vickers hardness of Nb_100−x B _x (30 ≦x ≦ 76) films exhibited the values of 1070 to 2060 kg mm².     

Polycrystalline Si1-x Ge x thin film deposition by rapid thermal chemical vapor deposition

Polycrystalline silicon germanium (poly-Si_1−xGe_x) thin films on a-Si film have been deposited by rapid thermal chemical vapor deposition (RTCVD) with SiH₄–GeH₄–H₂. Effect of GeH₄/SiH₄ and deposition temperature on stoichiometry (x), Si-Ge binding character, composition, hydrogen configuration, crystallinity, preferred orientation, grain size, and surface roughness of poly-Si_1−xGe_x films has been investigated. Poly-Si_1−xGe_x deposited on the substrate with amorphous silicon buffer layer on oxide shows better crystallinity and contains the less amount of oxygen than the one deposited directly on the oxide surface. At low temperature region, the Ge–H bond with the small amount of Si–H₂ bond is dominant but all hydrogen bonds are desorbed at high temperature. All films have polycrystalline phase and the grain size and (111) orientation increased with increasing deposition temperature in which Ge content also increases at the fixed gas flow rate of GeH₄ to total source gas. Poly-Si_1−xGe_x/Si thin film transistors (TFT) are fabricated and hydrogen during post-hydrogenation process preferentially is attached to Ge dangling bond and the TFT characteristics could be improved.     

Orientation of the BSCCO films prepared by low-pressure single-aerosol source metallorganic chemical vapour deposition

Thin films (0.7–0.8 μm) of Bi₂Sr₂CaCu₂O_x were deposited by low-pressure metallorganic chemical vapour deposition with a single aerosol source. The influence of the deposition parameters on the orientation of the films was studied. It was established that low deposition rate, high deposition temperature and the presence of the liquid phase resulted in films with predominant c-orientation.     

Characterizations of trimetallic heteronuclear Bi1−x La x [Fe(CN)6]·n(H2O) complexes and their thermal decomposition products

Heteronuclear Bi_1−x La _x [Fe(CN)₆]·nH₂O complexes were synthesized, and their crystal structures and thermal decomposition process were investigated by X-ray diffraction (XRD), thermogravimetry analysis (TGA), Auger electron spectroscopy (AES) with scanning electron microscope (SEM), and transmission electron microscopy (TEM). The crystal system of the complexes was orthorhombic having n = 4 for x = 0–0.7 and was hexagonal having n = 5 for x = 1.0. Their mixture was confirmed for x = 0.8 and 0.9. The lattice parameters for the orthorhombic increased with increasing the x value for the complexes. The single phase of trimetallic perovskite-type Bi_1−x La _x FeO₃ was obtained by its thermal decomposition at low temperature. The crystal system was hexagonal for BiFeO₃ (x = 0) and orthorhombic for x = 0.1–1.0. In the case of the decomposed perovskite sample, the lattice parameters decreased with increasing x values for Bi_1−x La _x FeO₃. The particle size was ca. 30 nm for Bi_0.2La_0.8FeO₃ obtained by thermal decomposition at 500 °C and it grew with an increase in decomposition temperature. For the Bi_0.5La_0.5FeO₃, AES showed that the elemental distributions of Bi, La, and Fe on the surface were very homogeneous for the sample decomposed at 700 °C.     

Solution-sol-gel processing of superconductors

Bulk materials and thin films of pure and homogeneous YBa₂Cu₃O_7−x and Bi₂Sr₂CaCu₂O_8+x compounds were prepared by a nanocomposite solution-sol-gel (SSG) method. The superconducting oxides of YBa₂Cu₃O_7−x and Bi₂Sr₂CaCu₂O_8+x were prepared at very low temperatures i.e. 750°C and 850°C, respectively by SSG method. Pellets sintered from these nanophasic sol powders showed sharp resistivity drops atT _c ∼ 90°K for YBa₂Cu₃O_7−x andT _c∼67°K for Bi₂Sr₂CaCu₂O_8+x . Thin films were prepared using triphasic sol of Y, Ba, Cu and tetraphasic sol of Bi, Sr, Ca and Cu on MgO and SrTiO₃ substrates. The triphasic sol coated on SrTiO₃ substrates and calcined at 800°C for 12h showed the formation of superconducting phase, YBa₂Cu₃O_7−x with preferred orientation along theC-axis. X-ray diffraction patterns of the Bi₂Sr₂CaCu₂O_8+x films on MgO substrate showed the formation of the superconducting phase with preferential orientation along the C-axis and the microwave absorption data as a function of temperature of this film revealed the onset temperature to be 90°K.     

Crystal structure and IR spectra of Sr1? x La x Fe1? x Cd x O3?δ

Sr_1−x La _x Fe_1−x Cd _x O_3−δ solid solutions with x = 0.1 and 0.5 prepared at 1270 K are shown to have a cubic perovskite structure and the SrLaFeO₄ structure, respectively. In the range x = 0.25-0.4, the samples consist of a perovskite phase and SrLaFeO₄. As x increases from 0.2 to 0.5, the content of the perovskite phase gradually decreases, and that of the phase isostructural with SrLaFeO₄ increases. The IR spectra of the samples with x = 0.3−0.5 are similar to the spectrum of SrLaFeO₄. The Sr_2/3La_1/3FeO_3−δ ferrite has the perovskite structure, rather than the Sr₂LaFe₃O₈ structure. The synthesis of this ferrite proceeds through the formation of SrFeO_3−δ and LaFeO₃, followed by the mutual dissolution of these orthoferrites. Original Russian Text ? S.V. Smolenchuk, L.A. Bashkirov, M.V. Bushinskii, S.S. Dorofeichik, 2007, published in Neorganischeskie Materialy, 2007, Vol. 43, No. 5, pp. 621–625.     

Kinetics of the γ → α-alumina phase transformation by quantitative X-ray diffraction

This work reports the kinetics of α-alumina transformation from γ-alumina, prepared by the sol-gel method from a solution of saturated aluminum nitrate and urea. The γ-alumina phase transformed directly into α-alumina at 750, 800, 850 and 900 ^oC, without any intermediate phases, such as θ- or δ-alumina. The kinetics of γ → α-alumina phase transformation was monitored by determination of α-alumina fraction formed through quantitative X-ray diffraction (XRD), with calcium fluoride added as an internal standard. The crystallised fractions of α-alumina increased sigmoidally with time, indicating that the γ → α-alumina phase transformation had a nucleation and growth mechanism. The kinetic parameters for this transformation were determined through the Kolmogorov–Johnson–Mehl–Avrami (KJMA) model and the Arrhenius’ law. The apparent activation energy, the Avrami exponent, n, and the t _0.75/t _0.25 ratio determined for the transformation were, respectively, of (201 ± 4) kJ mol⁻¹ (2.1 ± 0.2) and (2.1 ± 0.1). The apparent activation energy is lower than the values previously reported for the γ → α-alumina transformation, as a consequence of the high surface area (425 m²/g) of γ-alumina. The t _0.75/t _0.25 ratio of (2.1 ± 0.1) suggested that the α-alumina growth was plate-like, which was confirmed by the SEM micrograph of α-alumina.     

A study of microstructure and phase constitutions of the Cr–Ni surfacing layers deposited on Fe<Subscript>3</Subscript>Al intermetallic by SMAW

Three different Cr–Ni alloys were deposited on the surface of Fe₃Al intermetallic by shielded metal arc welding (SMAW) to investigate the weldability of this material. The microstructure, phase constitutions, and fine structures of Cr–Ni surfacing layers were analyzed via metalloscope, SEM, XRD, and TEM. The results indicated that the Fe₃Al/Cr–Ni joint shows no cracks when Cr25–Ni13 alloy was deposited. The surfacing layer consisted of austenite (A), pro-eutectoid ferrite (PF), carbide-free bainite (CFB), lath martensite (LM), and little acicular ferrite (AF). Phase constitutions of the joint included Fe₃Al, FeAl, γ-(Fe,C), γ-(Fe,Ni), NiAl, and Ni₃Al. The lattice orientation for CFB between α and γ phases was (110)_α//(111) _γ . Typical LM was composed of interlayer-carbide and α ferrite of 400 nm in length and 40 nm in width.     

Optical and electrical properties of Mg<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Zn<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>O thin films by sol–gel method

Mg _x Zn_1−x O (0 ≤ x ≤ 0.35) thin films have been deposited by sol–gel technique and the composition related structural, electrical, and optical properties are investigated. All the films have hexagonal wurtzite structure and the separation of MgO phase occurs when x = 0.3 and 0.35. With the increase of Mg content, the densification of the films decrease and band gap values increase. The maximum band gap value reaches 3.56 eV when x = 0.15. After Mg doping the conductivities of the Mg _x Zn_1−x O films are reduced greatly and the electrical current–voltage (I–V) characteristics show nonlinearity for x > 0.15.     

Crystal structure and magnetic properties of high-coercivity Sr1 ? xPrxFe12 ? xZnxO19 solid solutions

Sr_1−x Pr _x Fe_{12 − x} Zn _x O₁₉ ferrites with x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5 have been prepared by solid-state reactions between praseodymium, iron, and zinc oxides and strontium carbonate in air at 1470 K. According to X-ray diffraction results, the samples with x ≤ 0.2 were single-phase and those with 0.3 ≤ x ≤ 0.5 contained, in addition to the magnetoplumbite phase, small amounts of α-Fe₂O₃, ZnFe₂O₄, and PrFeO₃. The mixed-phase samples further fired twice at 1470 K for 4 and 2 h contained no impurity phases at x = 0.3 and contained only α-Fe₂O₃ at x = 0.4 and 0.5. In the composition range 0 ≤ x ≤ 0.3, the a and c cell parameters, unit-cell volume V, and X-ray density ρ_x of the magnetoplumbite phase vary linearly according to the relations a(?) = 5.8869 − 0.0162x, c(?) = 23.027 + 0.449 x, V(?³)= 691.10 + 9.65x, and ρ_x(g/cm³) = 5.102 + 0.230 x. The highest degree of combined heterovalent substitution of Pr³⁺ for Sr²⁺ and Zn²⁺ for Fe³⁺ in the SrFe₁₂O₁₉ ferrite (formation of Sr_1−x Pr _x Fe_{12 − x} Zn _x O₁₉ solid solutions) at 1470 K is x = 0.32−0.36. The saturation magnetization per formula unit (n _s) of the x = 0.1 ferrite exceeds that of SrFe₁₂O₁₉ by 1.7% at 6 K and by 15.2% at 308 K. The 308-K n _s and coercive force (_σ H _c) of the x = 0.2 ferrite exceed those of SrFe₁₂O₁₉ by 7.6 and 8.5%, respectively.     

Cost-effective solar cells containing copper indium chalcogenides prepared by SILAR method

CuInSe₂ (CISe) and CuIn(Se_1−x S _x )₂ (CISeS) thin films have been prepared using successive ionic layer adsorption and reaction method (SILAR) to produce CuSe and In₂Se₃, which were subsequently heated in appropriated conditions. Glass, TCO, and TCO/TiO₂ were used as substrates. A duplex layer of TiO₂ had been deposited by spray-pyrolysis and doctor blade. The thermal treatment leading to the formation of the chalcogenide was carried out in two different atmospheres. The first treatment was an annealing step under argon atmosphere, where CISe is obtained. The second consisted of a sulfurization process, where sulfur powder is melted and the vapor mixed into the argon flux. The morphology and composition of the annealed films were characterized by GXRD, micro-Raman spectroscopy, and SEM/EDS. Raman spectra and EDS showed an almost complete replacement of the Se atoms by S atoms, leading to the formation of CuIn(Se_1−x S _x )₂, with x = 0.8. Etching the films in KCN solution was necessary to dissolve residual secondary phases. Preliminary solar cell prototypes prepared with CISe and CISeS show a clear photo-response, although the photocurrent and open circuit potential are still low. This is a promising first result, showing that CuInSe₂ and CuIn(Se_1−x S _x )₂ prepared by SILAR can be used in solar cells.     

Electron diffraction study of TlGa<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Ge<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>X<Subscript>2</Subscript> (X = S,Se, Te) nanofilms

The formation of thin TlGa_{1 − x} Ge _x X₂ (X = S, Se, Te) films has been studied by high-energy electron diffraction. The results demonstrate that the dopant (Ge) concentration influences the structure of the films (30 nm in thickness). The epilayer-substrate orientation relationships are identified.     

Magnetic and structural properties of Fe<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Pt<Subscript>100−<Emphasis Type="Italic">x</Emphasis></Subscript> on MgO(110) substrates

Fe _x Pt_100−x (70.1 ≤ x ≤ 83.4) thin films with ordered Fe₃Pt phase were grown successfully onto MgO(110) substrates by electron beam evaporation. The unit cell of ordered Fe₃Pt phase is elongated along c-axis direction and the thin films become more chemically ordered with decreasing Fe content. The magnetization of thin films shows a decrease when Fe content is around 79 at.%. The relationship between magnetic anisotropy and structural parameters suggests that the change of magnetic anisotropy in ordered Fe₃Pt thin films with different compositions most likely stems from the magnetocrystalline origin.     

Effect of Zn doping on structure and ferroelectric properties of PST thin films prepared by sol–gel method

(Pb _y Sr_1−y )Zn _x Ti_1−x O_3−x thin films were prepared on ITO/glass substrate by sol–gel process using dip-coating method. The phase structure, morphology and ferroelectric property of the thin film were studied. All the thin films show the typical perovskite phase structure. Both the crystallinity and c/a ratio of the perovskite phase increases initially and then decreases gradually with doping Zn in the thin film. Ferroelectric properties of the Zn-doped PST thin films, including ferroelectric hysteresis-loop, remnant polarization and coercive force, decrease gradually with increasing Zn. And the effect of Zn on ferroelectric properties is more obvious in PST thin film with high content of Pb than that with low Pb although the high lead thin film exhibits high intrinsic ferroelectric properties.     

Structure and photoelectric properties of Si<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Sn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> epilayers

Epitaxial layers of n-type Si_{1 − x} Snx (0 ≤ x ≤ 0.04) solid solution were grown by liquid phase epitaxy from tin-based solution melt confined between two horizontal Si(111) single crystal silicon substrates. The structure of epilayers was determined and the photosensitivity spectra of pSi-nSi_{1 − x} Snx (0 ≤ x ≤ 0.04) structures were studied at various temperatures. It is established that Si_0.96Sn_0.04 films have a perfect single crystal structure with (111) orientation and a subgrain size of 60 nm. The photosensitivity edge of the pSi-nSi_0.96Sn_0.04 structure is shifted to longer wavelengths as compared to that of the pSi-nSi structure. The photosensitivity of the pSi-nSi_0.96Sn_0.04 structure in the impurity absorption range depends on the temperature.     

Dielectric, ferromagnetic and ferroelectric properties of the (1 ? x)Ba0.8Sr0.2TiO3–xCoFe2O4 multiferroic particulate ceramic composites

The (1 − x)Ba_0.8Sr_0.2TiO₃–xCoFe₂O₄ ceramic composites (x = 0–1) were prepared by standard solid state reaction method. X-ray diffraction and SEM indicate the Ba_0.8Sr_0.2TiO₃ (BST) phase and CoFe₂O₄ (CFO) phase coexist in the composites. The dielectric constant and dielectric loss for the composites were studied as a function of frequency (40 Hz–1 MHz) and temperature (30–600 °C). Magnetic and ferroelectric tests show that the ceramic composites display ferromagnetic and ferroelectric properties simultaneously. The saturated polarization of the composites decrease with ferrite concentration increasing, while the remnant polarization of the composites increase with increasing ferrite concentration. The enhanced ferroelectricity of composites may be attributed to space charge contribution in the composites.     

Silicon-substituted hydroxyapatite composite coating by using vacuum-plasma spraying and its interaction with human serum albumin

The incorporation of silicon can improve the bioactivity of hydroxyapatite (HA). Silicon-substituted HA (Ca₁₀(PO₄)_6−x (SiO₄) _x (OH)_2−x , Si-HA) composite coatings on a bioactive titanium substrate were prepared by using a vacuum-plasma spraying method. The surface structure was characterized by using XRD, SEM, XRF, EDS and FTIR. The bond strength of the coating was investigated and XRD patterns showed that Ti/Si-HA coatings were similar to patterns seen for HA. The only different XRD pattern was a slight trend toward a smaller angle direction with an increase in the molar ratio of silicon. FTIR spectra showed that the most notable effect of silicon substitution was that –OH group decreased as the silicon content increased. XRD and EDS elemental analysis indicated that the content of silicon in the coating was consistent with the silicon-substituted hydroxyapatite used in spraying. A bioactive TiO₂ coating was formed on an etched surface of Ti, and the etching might improve the bond strength of the coatings. The interaction of the Ti/Si-HA coating with human serum albumin (HSA) was much greater than that of the Ti/HA coating. This might suggest that the incorporation of silicon in HA can lead to significant improvements in the bioactive performance of HA.