Calorimetry of matrix-isolated sodium nitrite NaNO<Subscript>2</Subscript>

Differential scanning calorimetry has been used to carry out a high-precision study of sodium nitrite NaNO₂ incorporated into different silicate nanoporous matrices. Heat-capacity maxima due to smeared ferroelectric phase transitions have been discovered. Characteristics (intensity, half-width, phase-transition temperature, etc.) of the maxima have been investigated. Heat-capacity maxima related to an incommensurable phase transition have been reliably identified. The maxima can be attributed to the formation of appropriate orientation of sodium-nitrite nanocrystals in matrix pores.     

Fundamental optical spectra of ferroelectric NaNO<Subscript>2</Subscript>

Polarized spectra of complete complexes for fundamental optical functions of the NaNO₂ ferroelectric at 77K in the region of 4–24 eV for E ‖ a, E ‖ b, and E ‖ c are calculated. For the first time, integral polarized curves of dielectric permeability and specific volumetric losses of electrons are factorized into elementary transverse and longitudinal components of transfer bands and their main parameters are determined. For the calculations, the experimental reflection spectra, methods of Kramer-Kronig, and joint Argand diagrams are used. On the basis of theoretical calculations for the zones and dielectric permeability, a scheme of the nature and localization of the obtained bands for the components of separation of ?₂ is proposed in accordance with the model of interband transitions.     

Fabrication of Cr<Subscript>2</Subscript>O<Subscript>3</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> composite nanofibers by electrospinning

PVA(Polyvinyl alcohol)/chromium nitrate/aluminum nitrate composite nanofibers were prepared by using sol–gel processing and electrospinning technique. By high temperature calcinating the above precursor fibers, Cr₂O₃/Al₂O₃ composite nanofibers were successfully obtained. The fibers were characterized by XRD, IR, and SEM, respectively. The results showed that the crystalline phase and the morphology of the fibers depended on the calcination temperatures.     

Reflectivity spectra of NaNO<Subscript>2</Subscript>-infiltrated synthetic opal

We analyze the reflectivity spectra of synthetic opal crystals (sphere diameters of 200, 240, and 290 nm) infiltrated with ferroelectric sodium nitrite (NaNO₂) after preannealing in air or argon. The reflectivity spectra of the opal samples show a band corresponding to the photonic band gap. Its position and shape strongly depend on the sphere diameter and annealing conditions. The spectra of the sodium-nitrite-infiltrated opal samples preannealed in air differ markedly from those of the samples preannealed in argon. The experimentally determined band gap position as a function of sphere diameter is compared to calculation results. Our data demonstrate that argon preannealing ensures effective infiltration of molten sodium nitrite into the pores of synthetic opal.     

Fabrication and characterization of epitaxial Ba<Subscript>0.6</Subscript>Sr<Subscript>0.4</Subscript>TiO<Subscript>3</Subscript>/LaNiO<Subscript>3 </Subscript>heterostructures

Epitaxial Ba0.6Sr0.4TiO3 (BST)/LaNiO3 (LNO) heterostructures were fabricated on LAO (100) substrates using pulsed laser deposition (PLD). Their structural properties were investigated by X-ray diffraction (XRD). The θ–2θ scans showed single crystalline BST and LNO layers with a (100) orientations perpendicular to the substrate plane. Phi scans (ϕ) on the (220) plane of BST layer indicated that the films have two in-plane orientations with respect to the substrate. The atomic force microscope (AFM) surface morphologies showed a smooth and crack-free surface with the average grain size of 55 nm and the root-mean-square (RMS) of 4.53 nm for BST films. Capacitance–voltage curves are measured. From the capacitance, a dielectric constant of 762, tunabilty of 82.81% and loss tangent of 0.032 are obtained. The current–voltage curve shows that the leakage current is 2.41 × 10⁻⁷ A/cm² under an applied voltage of 2 V.     

One-step electrochemical machining of superhydrophobic surfaces on aluminum substrates

A superhydrophobic surface on an aluminum substrate was fabricated by one-step electrochemical machining using the sodium chloride (NaCl) aqueous solution containing fluoroalkylsilane as the electrolyte. The resulting superhydrophobic surfaces showed a static water contact angle of 166° and a tilting angle of about 1°. The morphological features and chemical compositions were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), electron probe micro-analyzer (EPMA), and Fourier-transform infrared spectrometer (FTIR). It shows that the binary micrometer–nanometer-scale rough structures and the low surface energy coating were present on the aluminum surfaces. The resulting surfaces have good properties of anti-adhesion and self-cleaning. The durability of the superhydrophobic surfaces on aluminum substrates was also investigated. This preparation method is advantageous as it does not require acid electrolyte or a separate process to lower the surface energy, uses simple steps, and is environmental friendly and highly efficient.     

Fabrication of conductive SrRuO<Subscript>3</Subscript> thin film and Ba<Subscript>0.60</Subscript>Sr<Subscript>0.40</Subscript>TiO<Subscript>3</Subscript>/SrRuO<Subscript>3</Subscript> bilayer films on MgO substrate

Conductive SrRuO₃ (SRO) thin films have been grown on (100) MgO substrates by pulsed laser deposition (PLD) technique. Effects of oxygen pressure and deposition temperature on the orientation of SRO thin film were investigated. X-ray diffraction (XRD) θ/2θ patterns and the temperature dependent resistivity measurements indicated that oxygen pressure of 30 Pa and deposition temperature of 700 °C were the optimized deposition parameters. A parallel-plate capacitor structure was prepared with the SRO films deposited under optimized condition as an electrode layer and Ba_0.60Sr_0.40TiO₃ (BST) thin film as the dielectric layer. XRD Φ scans indicated a epitaxial relationship between BST and SRO on MgO substrate. The dielectric constant and loss tangent measured at 10 kHz and 300 K was 427 and 0.099 under 0 V bias, and 215 and 0.062 under 8 V bias, respectively. A tunability of 49.6% has been achieved with DC bias as low as 8 V. The C–V hysteresis curve and the P–E hysteresis loop suggested that the BST films epitaxially grown on SRO/MgO have ferroelectricity at room temperature. The induced ferroelectricity was believed to originate from the compressive strain between the epitaxial BST and SRO thin films. These results show the potential application of the BST/SRO heterostructures in microelectronic devices.     

Fabrication of thin films by sputtering deposition using (Ba<Subscript>0.3</Subscript>Sr<Subscript>0.7</Subscript>)(Zn<Subscript>1/3</Subscript>Nb<Subscript>2/3</Subscript>)O<Subscript>3</Subscript> ceramic as target

Dielectric ceramic thin films were fabricated on SiO₂ (110) substrates by the radio frequency (RF) magnetron sputtering method using (Ba_0.3Sr_0.7)(Zn_1/3Nb_2/3)O₃ microwave dielectric ceramic as target. The microstructure, components, and morphology of the thin films were investigated thoroughly. The results reveal that the experimental conditions can affect the growth of the thin films significantly. The main phases of the thin films are Ba_0.5Sr_0.5Nb₂O₆ and Ba_0.27Sr_0.75Nb₂O_5.78, which are of different composition from that of the ceramic target due to Zn loss. The thin films are polycrystalline with high-quality crystalline and are made up of dense rod-like structures. The growth mechanism of the thin films is discussed in particular.     

Fabrication of Ag<Subscript>3</Subscript>PO<Subscript>4</Subscript>-AgBr-PTh composite loaded on Na<Subscript>2</Subscript>SiO<Subscript>3</Subscript> with enhanced visible-light photocatalytic activity

A novel Ag₃PO₄-AgBr-PTh composite loaded on Na₂SiO₃ was synthesized for enhanced visible-light photocatalytic activity. The photocatalytic activity of the samples was evaluated by photodegrading rhodamine B (RhB) under visible light irradiation. The main reactive species and possible photocatalytic mechanism were also discussed. As a result, the Ag₃PO₄-AgBr-PTh composite loaded on Na₂SiO₃ exhibited enhanced photocatalytic activity for RhB compared with Ag₃PO₄ under visible-light irradiation. Additionally, it was demonstrated that the hole (h⁺) and superoxide radical (?O ₂ ^? ) were the major reactive species involving in the RhB degradation. PTh played vital role for the enhanced photocatalytic activity of Ag₃PO₄-AgBr-PTh-Na₂SiO₃ composite, which offered an electron transfer expressway and accelerated the transfer of the electrons from the CB of AgBr into Ag₃PO₄. This work could provide a new perspective for the synthesis of Ag₃PO₄-based composites and the improvement of photocatalytic activity of Ag₃PO₄.     

Refractive index of Al<Subscript>3</Subscript>C<Subscript>2</Subscript>B<Subscript>48</Subscript> aluminum borocarbide crystals

Aluminum borocarbide single crystals have been grown from an Al-based solution melt. The crystal lattice parameters have been determined, the dispersion of the refractive index in a 0.55–1.3 μm wavelength interval has been studied, and the temperature coefficient of the refractive index in a 300–600 K range has been measured. The crystals are characterized by a high refractive index in the visible spectral range in combination with at a high hardness, which makes them of interest for jewelry, as well as for both traditional and X-ray optics.     

Liquid-phase epitaxy of NdAl<Subscript>3</Subscript>(BO<Subscript>3</Subscript>)<Subscript>4</Subscript> and Yb-doped YAl<Subscript>3</Subscript>(BO<Subscript>3</Subscript>)<Subscript>4</Subscript>

Epitaxial layers of NaAl₃(BO₃)₄ (NAB) and YAl₃(BO₃)₄〈Yb〉 (YAB〈Yb〉) containing up to 10 at % Yb have been grown by liquid-phase epitaxy on YAB substrates. Their growth kinetics have been studied at relative supersaturations of the high-temperature solution from 2 × 10^?2 to 16 × 10^?2. The ytterbium concentration in YAB〈Yb〉 has been shown to vary little during the epitaxial process. Near the edges of the substrate, the surface morphology of the layers is complicated by vicinals, which have a spiral form in the case of YAB〈Yb〉. On \(\{ 10\overline 1 1\} \) YAB substrates, homogeneous single-crystal NAB films have been grown.     

Fabrication and dielectric properties of textured Na<Subscript>0.5</Subscript>Bi<Subscript>0.5</Subscript>TiO<Subscript>3</Subscript>-BaTiO<Subscript>3</Subscript> ceramics by RTGG method

Grain-oriented Na_0.5Bi_0.5TiO₃-BaTiO₃ (NBTBT) ceramics were fabricated by reactive-templated grain growth using plate-like Bi_2.5Na_3.5Nb₅O₁₈ (BNN) as templates. The specimens are composed of NBTBT perovskite phase and BNN lay-structured phase. Textured ceramics have a brick-wall microstructure with strip-like grains aligning in the direction parallel to the casting plane and exhibit an {h00} preferred orientation. The texture fraction increases initially, and then decreases with increasing sintering temperature. The optimal sintering temperature is 1,185 °C where the texture fraction has a maximum value of 0.58 and d₃₃ is 98 pC/N. The textured NBTBT ceramics show evidence of relaxor ferroelectrics with diffuse phase transition and frequency dispersion because of composite biphasic structure.     

Fabrication of La<Subscript>3</Subscript>TaO<Subscript>7</Subscript> using a new precursor solution route by chemical solution method

La₃TaO₇ (LTO) has been fabricated using a new precursor solution route by chemical solution method. The newly developed LTO precursor solution was obtained in ambient atmosphere. A serious of studies on the properties of LTO precursor gel and its powder annealed at different temperatures were presented in order to understand the decomposition of LTO precursor gel and the growth behavior of LTO. The single phase LTO powder and LTO film on textured Ni–W substrate were obtained after annealed at 1,100° in a gas mixture of Ar-4% H₂. But it should be pointed out that LTO film was annealed by adopting a rapid elevated temperature processing (RETP) method. X-ray diffraction shows that the LTO film on Ni–W tape was highly oriented, and its out-of-plane texture is very close to that of the underlying Ni–W substrate. The SEM investigation of LTO film reveals a dense, smooth, pinhole-free and crack-free microstructure for coated buffer. These results offer the potential to use the LTO film prepared by the new precursor solution route as a buffer layer for further manufacturing other buffer layer in coated conductors.     

Fabrication of NaZr<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>-type ceramic materials by spark plasma sintering

Ceramic materials based on Ca_0.5Zr₂(PO₄)₃ and NaFeNb(PO₄)₃, structural analogs of NaZr₂(PO₄)₃ (NZP), were prepared by spark plasma sintering. At sintering temperatures of 1100–1200 and 880°C and sintering times of 12 and 3 min, the relative densities reached were 99.1 and 99.9%, respectively. According to X-ray diffraction data, the sintering process caused no changes in phase composition. The ceramics had a dense, homogeneous microstructure and ranged in grain size from 0.5 to 2.5 μm.     

Magnetoresistance of La<Subscript>0.67</Subscript>Ca<Subscript>0.33</Subscript>MnO<Subscript>3</Subscript> films grown on substrates with orthorhombically distorted unit cells

We have studied the structure and magnetoresistance of 40-nm-thick epitaxial La_0.67Ca_0.33MnO₃ (LCMO) films grown by laser deposition on (001)-oriented NdGaO₃ (NGO) substrates. The manganite layers were oriented so that the b axis was perpendicular to the substrate plane and occurred under the action of inhomogeneous biaxial mechanical stresses. The negative magnetoresistance of the LCMO films in the vicinity of the ferromagnetic spin ordering was about 71% (μ₀ H = 1 T). The observed azimuthal anisotropy of the magnetotransport properties of 40-nm-thick LCMO/(001)NGO films can be explained within the framework of a model of anisotropic magnetoresistance taking into account the presence of the preferred orientation of the spontaneous magnetization.     

Orientation controlling of Pb(Zr<Subscript>0.53</Subscript>Ti<Subscript>0.47</Subscript>)O<Subscript>3</Subscript> thin films prepared on silicon substrates with the thickness of La<Subscript>0.5</Subscript>Sr<Subscript>0.5</Subscript>CoO<Subscript>3</Subscript> electrodes

Pb(Zr_0.53Ti_0.47)O₃ (PZT) thin films were prepared on La_0.5Sr_0.5CoO₃ (LSCO) coated Si substrates by a sol–gel route. The thickness of LSCO electrode was found to modify the preferential orientation of PZT thin films, which consequently affected the dielectric and ferroelectric properties. (100) textured PZT films with dense columnar structure could be obtained on the top of (110) textured LSCO with thickness of 230 nm. PZT thin films prepared on the optimized LSCO films exhibit the enhanced dielectric constant and remnant polarization of 980 and 20 μC/cm², respectively.     

New forms of In<Subscript>2</Subscript>Se<Subscript>3</Subscript> and Ga<Subscript>2</Subscript>Se<Subscript>3</Subscript> prepared by reacting InAs and GaAs substrates with selenium

Ga₂Se₃ and In₂Se₃ prepared through heterovalent substitution during thermal annealing of single-crystal gallium arsenide and indium arsenide substrates in selenium vapor in a quasi-closed system have been characterized by electron diffraction, scanning electron microscopy, and X-ray microanalysis. Cubic phases of In₂Se₃ (a ₀ = 1.1243 nm and a ₀ = 1.6890 nm) and Ga₂Se₃ (a ₀ = 1.0893 nm and a ₀ = 1.6293 nm) have been identified for the first time.     

A novel Y<Subscript>3</Subscript>ZnAl<Subscript>3</Subscript>SiO<Subscript>12</Subscript> microwave dielectric ceramic for microwave communication application as substrates

Novel microwave dielectric ceramic Y₃ZnAl₃SiO₁₂ were synthesized by solid-state route. The crystal structure of synthesized samples was characterized by X-ray diffraction and refined with Rietveld method. Microstructure and microwave dielectric properties of Y₃ZnAl₃SiO₁₂ ceramics were investigated using Scanning Electron Microscopy and Hakki–Coleman method. X-ray data display that major phase of Y₃ZnAl₃SiO₁₂ is isostructural to Y₃Al₅O₁₂ with a cubic garnet structure and space group of Ia-3d, which is composed of (Al/Si)O₄ tetrahedron, (Zn/Al)O₆ octahedron and YO₈ dodecahedron, besides minor Y₂SiO₅ secondary phase. The distribution of grain sizes is closer to Gauss distribution. Bulk density of samples has a similar variation curve with Q*f of samples. Y₃ZnAl₃SiO₁₂ ceramics exhibit excellent microwave dielectric properties: ε_r?=?10.2, Q*f?=?37938.2 (@9.47 GHz), τ _f ?=??31.7 ppm/°C at sintering temperature of 1500 °C. Our results indicate Y₃ZnAl₃SiO₁₂ could be a potential material for millimeter wave communication systems as microwave substrates.     

Phase equilibrium and properties of solid solutions of PbTiO<Subscript>3</Subscript>-PbZrO<Subscript>3</Subscript>-PbNb<Subscript>2/3</Subscript>Mg<Subscript>1/3</Subscript>O<Subscript>3</Subscript>-PbGeO<Subscript>3</Subscript> system

Phase diagrams of three sections of the four-component system PbTiO₃-PbZrO₃-PbNb_2/3Mg_1/3O₃-PbGeO₃ are plotted (at 20°C) and electrophysical properties of solid solutions are studied. It is found that morphotropic areas, in which dielectric, piezoelectric, and elastic properties are extreme, have a wider concentration interval than in binary systems serving as the base for the studied solid solutions. In monophase areas, isosymmetrical fields (phase states) divided by areas of constant structural parameters are revealed. An explanation of the observed effects based on the real defect structure of objects is proposed.