Electrodeposition of bismuth, tellurium, and bismuth telluride thin films from choline chloride–oxalic acid ionic liquid

This article presents a series of preliminary results regarding the electrodeposition of bismuth, tellurium, and bismuth telluride films at 60 °C from ionic liquids, containing a mixture of choline chloride and oxalic acid (ChCl–OxA). Ten millimolar concentration solutions of BiCl₃ and TeO₂ were used as precursors in this supporting electrolyte. Cyclic voltammetry and electrochemical impedance spectroscopy techniques were used to demonstrate the deposition processes on Pt and Cu electrodes. Long-time electrolyses (30–120 min) performed at 60 °C with potential control (between ?0.22 and ?0.37 V vs. Ag reference electrode) have resulted in films deposited on copper substrate. Film surfaces were studied by scanning electron microscopy and analyzed by energy dispersive X-ray spectroscopy. The results of this study show that ChCl–OxA ionic liquid may be considered as a promising substitute of aqueous baths for Bi, Te or Bi₂Te₃ film plating.     

TIC-09-Mesoporous Niobium-Based Mixed Metal Oxides Containing Mo, V, and Te for Propane Oxidative Dehydrogenation

The novel thermally stable mesoporous multicomponent MNbO _x (M = V, Mo, and Te) mixed metal oxides were successfully synthesized by evaporation-induced self-assembly (EISA) employing niobium oxide as a major structural component. The formation of nanocrystalline M1 phase as part of the ordered mesoporous structure was investigated. These mixed metal oxide phases displayed good thermal stability (up to 400 °C), large pore sizes (up to 14 nm), high surface areas (up to 230 m²/g) and flexible inorganic wall compositions. Thermally stable mesoporous Nb₂O₅ supported metal M/Nb (M = MoVTeNb) oxides were obtained by incipient-wetness impregnation (IWI) technique. The comparison between mesoporous bulk mixed and supported mixed metal oxides (MNbO _x and M/Nb) were addressed. The catalytic roles of the constituent metal oxides were investigated in oxidative dehydrogenation (ODH) of propane. The methods described in this paper represent promising synthetic approaches for the design of novel catalytic mixed metal oxides.     

Synthesis and microstructural characterization of Bi12SiO20 (BSO) thin films produced by the sol–gel process

We have produced Bi₁₂SiO₂₀ (BSO) thin films using the sol–gel process. The stable sol was synthesized using Bi(NO₃)₃·5H₂O and Si(OC₂H₅)₄ (TEOS) as the precursors, acetic acid and 2-ethoxyethanol as the solvents, and ethanolamine as the stabilizer. The stability of the solution, which depends on the concentration and the R_h value (R_h = [H₂O]/[M]), directly affects the microstructure of the BSO thin film. We determined that the optimal concentration for the preparation of BSO thin films is 0.76 M. The influences of the substrates, the annealing temperature, the concentration and the R_h = value of the solution on the microstructure of the Bi₁₂SiO₂₀ thin films were investigated. X-ray diffraction (XRD) showed that the Bi₁₂SiO₂₀ starts to form at 500 °C and that single-phase Bi₁₂SiO₂₀ polycrystalline thin films are formed at 700 °C. The coated films were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM).     

Enhanced Thermoelectric Performance of <Emphasis Type="Italic">c</Emphasis>-Axis-Oriented Epitaxial Ba-Doped BiCuSeO Thin Films

We reported the epitaxial growth of c-axis-oriented Bi_1?xBa_xCuSeO (0?≤ x ≤?10%) thin films and investigated the effect of Ba doping on the structure, valence state of elements, and thermoelectric properties of the films. X-ray photoelectron spectroscopy analysis reveal that Bi³⁺ is partially reduced to the lower valence state after Ba doping, while Cu and Se ions still exist as +?1 and ??2 valence state, respectively. As the Ba doping content increases, both resistivity and Seebeck coefficient decrease because of the increased hole carrier concentration. A large power factor, as high as 1.24 mWm^?1 K^?2 at 673 K, has been achieved in the 7.5% Ba-doped BiCuSeO thin film, which is 1.5 times higher than those reported for the corresponding bulk samples. Considering that the nanoscale-thick Ba-doped films should have a very low thermal conductivity, high ZT can be expected in the films.     

Characterization of Bi2O3 thin films for doping photoluminescent Er3+ ions

Undoped and Er³⁺-doped Bi₂O₃ thin films were sputter-deposited on Si(100) substrates. Sufficiently oxidized Bi₂O₃ films with refractive indices between 2.17?2.23 were obtained at a wavelength of 633 nm; these values are comparable to those of bulk Bi₂O₃ crystals. While the film composition was stable for deposition temperatures between room temperature (RT) and 450 °C, the refractive index steeply decreased above 450 °C and reached 1.4 at 600 °C. The lowering of the optical transmittance spectra indicated aggregation of metallic Bi and darkening of the film. All films exhibited X-ray diffraction patterns of α-Bi₂O₃. The direct and indirect bandgap energies derived from the Tauc plots were 3.4–3.7 eV and 1.9–2.5 eV, respectively, depending on the O₂ flow rate and deposition temperature. Upon excitation of Er³⁺-doped Bi₂O₃ films at 532 nm, Er³⁺ emissions peaking at 1537 and 1541 nm appeared, and the photoluminescence spectra included fine structures reflecting crystal-field splitting. Resonant excitation of Er³⁺ 4f levels and indirect excitation via the defect levels of Bi₂O₃ followed by energy transfer to Er³⁺ contributed to the emission. The films deposited at RT with Er concentrations of 2 at.% had the emission intensity of Er³⁺, but concentration quenching strongly suppressed the Er³⁺ emission because the doped Er³⁺ ions stayed inside the Bi₂O₃ crystals. At deposition temperatures above 400 °C, the concentration quenching was mitigated possibly because out-diffusion of Er³⁺ ions reduced the effective number of Er³⁺ ions in the Bi₂O₃ crystalline domains.     

Temperature–stable dielectrics based on Cu–doped Bi2Mg2/3Nb4/3O7 pyrochlore ceramics for LTCC

Temperature–stable dielectrics based on Cu–doped Bi₂Mg_2/3Nb_4/3O₇ pyrochlore ceramics were prepared by conventional solid–state reaction. Microstructure analysis indicates that all of the specimen maintain the cubic pyrochlore phase, a fluorite–like phase of Bi₃NbO₇ and a Bi₅Nb₃O₁₅ formed for Cu doping. The dielectric constant is dominated by densification of samples and secondary phases, while the dielectric loss is related by the secondary phases, grain boundaries, and leakage current characteristics. The (1-x)BMN - xCuO(x = 0.1 mol%) ceramic sintered at 925 °C shows excellent dielectric properties with dielectric constant of ~184.06, dielectric loss of ~0.0017 and near zero τ_ε (?20 ppm/°C) is obtained at sintering temperature of 925 °C, which could be a promising candidate for LTCC.     

Synthesis and Photocatalytic Performance of Bi<Subscript>12</Subscript>O<Subscript>17</Subscript>Cl<Subscript>2</Subscript> Semiconductors Calcined at Different Temperatures

In the current investigation a series of oxygen-rich bismuth oxychloride Bi₁₂O₁₇Cl₂ samples through an ethylene glycol-solvothermal route were constructed at different calcination temperatures and fully characterized by X-ray diffraction patterns, scanning electron microscopy, Fourier transformed infrared spectroscopy, X-ray photoelectron spectroscopy, UV–Vis diffuse reflectance spectra, X-ray energy dispersion spectroscopy, and photoluminescence spectra. It was demonstrated that the calcination temperatures indeed had a crucial effect on the crystallinity, grain size, morphology, optical property, and charge carrier separation of Bi₁₂O₁₇Cl₂ series. These Bi₁₂O₁₇Cl₂ samples showed significantly improved photocatalytic degradation over dye Rhodamine B and colorless antibiotic tetracycline hydrochloride. Particularly, the best candidate, the sample 350 °C—Bi₁₂O₁₇Cl₂ could show apparent reaction rate constants that were nearly 28.2, 1.2 times of N–TiO₂ over Rhodamine B and tetracycline hydrochloride, respectively. The possible reason of enhancing photocatalytic performance by various Bi₁₂O₁₇Cl₂ samples calcined at different temperatures was discussed and major oxidative radicals maybe generated during photocatalytic processes were detected.     

Preparation and electrical properties of Sm-doped Bi2Ti2O7 thin films prepared on Pt (111) substrates

Crack-free Sm-doped Bi₂Ti₂O₇ (Sm:BTO) thin films with strong (111) orientation have been prepared on Pt (111) substrates using a chemical solution deposition (CSD) method. The structural properties and crystallizations were studied by X-ray diffraction. The surface morphology and quality were examined using atomic force microscopy (AFM). The insulating and dielectric properties were also evaluated at room temperature. The results demonstrate that the Sm:BTO films exhibit improved electrical performances as compared to the pure Bi₂Ti₂O₇ thin films and suggest a strong potential for utilization in microelectronics devices.     

Optical and structural properties of ZnO NPs and ZnO–Bi2O3 nanocomposites

Pure ZnO and ZnO–Bi₂O₃ nanocomposites with 5 wt% and 10 wt% of Bi₂O₃ content were synthesized using the co-precipitation method. Optical properties such as refractive index (n), extinction coefficient (k), bandgap (E_g), and Urbach energies, as well as the band structure, were determined by modeling the experimental transmittance and reflectance UV–Vis spectra. The deduced bandgap and Urbach energies for pure ZnO (3.758 eV) increase with the increase of the doping degree of Bi₂O₃ in ZnO–Bi₂O₃ nanocomposite films. X-ray diffraction and scanning electron microscopy (SEM) was used to study the structural and morphological properties of these nanocomposite films. Pure ZnO and nanocomposites with Bi₂O₃ exhibit crystalline domains with wurtzite hexagonal structures, and as the doping degree of Bi₂O₃ increases, the crystallite size decreases. Based on SEM micrographs, the ZnO nanoparticles (NPs) structure shows the presence of aggregation. Moreover, Bi₂O₃ NPs in the nanocomposite film led to the further aggregation in the form of large rods. The elemental and chemical properties of the nanocomposites were investigated using infrared and energy-dispersive X-ray spectroscopy. The charge transfer process in the studied system is between ZnO and Bi₂O₃ conduction bands. Density-functional theory (DFT) calculations were performed for ZnO, Bi₂O₃, and ZnO-Bi₂O₃ compounds to investigate structural, optical, and electronic properties, being in agreement with the experimental results.     

Synthesis and Characterization of Polyaniline:TiO2 Nanocomposites

Thin films of polyaniline (PANi) and PANi:titanium oxide (TiO₂) composites have been synthesized by sol—gel spin coating technique. The TiO₂ powder of particle size 50–60 nm was synthesized by sol–gel technique and the polyaniline was synthesized by chemical oxidative polymerization of aniline. The composite films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) Fourier transform infrared (FTIR) and UV-vis spectroscopy, and the results were compared with polyaniline films. The intensity of the diffraction peaks for PANi:TiO₂ composites is lower than that for TiO₂. The characteristic FTIR peaks of PANi were found to shift to a higher wave number in the PANi:TiO₂ composite. These observed effects have been attributed to the interaction of TiO₂ particles with PANi molecular chains. The room temperature resistivity of polyaniline:nano-TiO₂ composite is 3.43 × 10³ Ω cm and the resistivity of pure nano-TiO₂ particles is 1.60 × 10⁶ Ω cm.     

Tailoring microstructure and photovoltaic effect in multiferroic Nd-substituted BiFeO3 ceramics by processing atmosphere modification

This study highlights significant effects of processing atmosphere ratio (O₂/N₂) on microstructure, impurity phases, atomic hybridization, band gap, and photovoltaic properties in (Bi_0.93Nd_0.07)FeO₃ (BFO7Nd) ceramics. A Rietveld-refinement analysis indicates increased oxygen and bismuth vacancies in the specimens processed in the O₂-rich atmosphere (hereafter called O₂-rich-atmosphere specimens). In the matrix containing mainly Fe³⁺ ions, Fe⁴⁺ cations were identified with O₂ concentration decreasing in the atmosphere by Fe K/L-edges synchrotron X-ray absorption. Oxygen K-edge absorption reveals reduced hybridizations of the O 2p–Fe 3d and the O 2p–Bi 6sp orbitals in the O₂-rich-atmosphere specimens. Photovoltaic effects in the ITO/BFO7Nd/Au heterostructures under near-ultraviolet irradiation (λ = 405 nm) exhibit strong dependences on O₂/N₂ ratio. A p-n-junction model was used to describe open-circuit voltage and short-circuit current density as functions of irradiation intensity. The calculated carrier densities (in BFO7Nd ceramics) and p-n-junction widths (in the dark) are ～10²³ m^?3 and a few hundred nanometers, respectively.     

Surface-initiated growth of copper using isonicotinic acid-functionalized aluminum oxide surfaces

Isonicotinate self-assembled monolayers (SAM) were prepared on alumina surfaces (A) using isonicotinic acid (iNA). These functionalized layers (iNA-A) were used for the seeded growth of copper films (Cu-iNA-A) by hydrazine hydrate-initiated electroless deposition. The films were characterized by scanning electron microscopy (SEM), electron-dispersive X-ray spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and advancing contact angle measurements. The films are Cu⁰ but with surface oxidation, and show a faceted morphology, which is more textured (R _q = 460 ± 90 nm) compared to the SAM (R _q = 2.8 ± 0.5 nm). In contrast, growth of copper films by SnCl₂/PdCl₂ catalyzed electroless deposition, using formaldehyde (CH₂O) as the reducing agent, shows a nodular morphology on top of a relatively smooth surface. No copper films are observed in the absence of the isonicotinate SAM. The binding of Cu²⁺ to the iNA is proposed to facilitate reduction to Cu⁰ and create the seed for subsequent growth. The films show good adhesion to the functionalized surface.     

Structural,thermal, dielectric and ferroelectric properties of K0.5Bi0.5TiO3 ceramics

Dense K_0.5Bi_0.5TiO₃ (KBT) lead-free ceramics were prepared by conventional solid reaction route. Their temperature behavior (up to 600 °C) was investigated by X-ray diffraction, DSC, dielectric spectroscopy and electric field-polarization technique. The first temperature dependent Raman scattering studies were also performed. X-ray and Raman scattering results show that samples exhibit a single perovskite structure with cubic symmetry at temperatures higher than approximately 400 °C and with coexistence of the cubic and tetragonal phases below this temperature. Two structural phase transitions between tetragonal phases in temperature range 200–225 °C and between tetragonal and cubic ones near 400 °C are observed. The content of the tetragonal phase increases with decreasing temperature and at room temperature it reaches more than 70%. Temperature- dependent P-E loops and pyroelectric data revealed a polar behavior in KBT up to about 400 °C, which means that the intermediate phase (～270–380 °C) is rather ferroelectric than antiferroelectric.     

Characterization of CuInS2 thin films prepared by one-step electrodeposition

CuInS₂ thin films were fabricated by one-step electrochemical deposition from a single alkaline aqueous solution and using conductive glass as the substrate. The electrolyte consisted in 0.01 mol L^?1 CuCl₂, 0.01 mol L^?1 InCl₃, 0.5 mol L^?1 Na₂SO₃ and 0.2 mol L^?1 Na₃C₃H₅O(COO)₃ (CitNa) at pH 8. The films were analyzed using a variety of techniques such as X-ray diffractometry, micro-Raman spectroscopy, X-ray energy dispersive spectroscopy, X-ray photoelectron spectroscopy and photoelectrochemistry. After carrying out a thermal treatment in sulfur vapor, chalcopyrite CuInS₂ thin films were obtained. Etching the films in KCN solution was found to be a key step, enabling a final adjustment in the stoichiometry. These thin films exhibited p-type semiconductor behavior with the bandgap of 1.43 eV. The results show that electrodeposition provides a cost-effective and versatile method for the preparation of thin films of CuInS₂, even when acidic precursors need to be avoided.     

The Influence of the Precursor on the Formation of Bi2O3 Polymorphs in CSD‐Derived Thin Films

This work examines the synthesis and characterization of crack‐free, β‐Bi₂O₃ thin films prepared on Pt/TiO₂/SiO₂/Si or corundum substrates using the sol‐gel method. We observed that the Bi‐based precursor has a pronounced influence on the β‐Bi₂O₃ phase formation. Well‐crystallized, single β‐Bi₂O₃ thin films were obtained from Bi‐2ethylhexanoate at a temperature of 400°C. In contrast, thin films deposited from Bi‐nitrate and Bi‐acetate resulted in non‐single Bi₂O₃ phase formation. TEOS was used for the stabilization of the β‐Bi₂O₃ phase. The phase composition of the thin films was characterized by means of X‐ray diffraction (XRD), whereas the morphology and thickness of the thin films were studied using scanning electron microscopy (SEM). The β‐Bi₂O₃ films' dielectric properties were characterized utilizing microwave‐frequency measurement techniques: (1) the split‐post dielectric resonator method (15 GHz) and (2) the planar capacitor configuration (1–5 GHz). The dielectric constant and dielectric loss measured at 15 GHz were 257 and 7.5 × 10^?3, respectively.     

Microwave dielectric properties of bismuth zinc niobate thin films deposited on alumina by pulsed laser deposition

Bi₂Zn_2/3Nb_4/3O₇ thin films were prepared on Al₂O₃ substrates by pulsed laser deposition. The phase compositions and microstructures were characterized by X-ray diffraction and atomic force microscopy. The as-deposited films were all amorphous in nature. All films were crystallized after the post annealing at the temperature range of 700–900 °C for 30 min in air. The texture characteristics change with annealing temperature. A split post dielectric resonator method was used to measure the microwave dielectric performance at the resonant frequencies of 10, 15 and 19 GHz. For the films annealed at 900 °C, the preferential orientation is similar to the monoclinic BZN bulk. The microwave dielectric constants at 10, 15 and 19 GHz are 69.4, 58.9 and 47.9, respectively, which are closer to these of the monoclinic BZN bulk.     

Microstructural and microwave dielectric properties of LZT (Li2ZnTi3O8) ceramics sintered in presence of bismuth borate glass for LTCC applications

In the present research, the Li₂ZnTi₃O₈(LZT) ceramics were synthesized throughout solid-state ceramic processing, then mixed with bismuth borate (BiBO) glass prepared based on conventional melt quenching method. Wetting behavior of BiBO glass on the LZT ceramic substrate was monitored by hot stage microscopy. Afterward, dielectric LZT ceramics containing different amounts of BiBO glass (0.25–6 wt%) were sintered at various temperatures. X-ray diffraction and electron back scatter diffraction examinations revealed the presence of two crystalline phases of Li₂ZnTi₃O₈ and Bi₂Ti₂O₇. The maximum value of relative density (above 95%) was obtained in the case of specimens contained more than 5 wt% glass. The microwave dielectric properties of the finally sintered BiBO glass containing LZT ceramics were as follows: dielectric constant (ε_r) = 21.44–25.09, quality factor (Q × f) = 10839–54708 GHz and temperature coefficient of resonant frequency (τ_f) = (? 15.58) ? (? 12.86)ppm/°C.     

Sonochemical Synthesis,Characterization and Sonocatalytic Performance of Terbium-Doped CdS Nanoparticles

Terbium-doped cadmium sulfide nanoparticles with different terbium contents were successfully synthesized via sonochemical route. The prepared samples were characterized by X-ray diffraction, scanning electron microscopy, photoelectron X-ray spectroscopy, and UV–Vis diffuse reflectance spectroscopy techniques. The as-prepared nanocatalyst were used for sonocatalytic degradation of Methylene Blue. Among the different amounts of dopant, 8 % Tb-doped CdS showed the highest sonocatalytic activity. The order of inhibitory effect of radical scavengers was 1, 4 Benzoquinone > SO₃ ^2? > CO₂ ^3?> I^?. The effects of various parameters such as initial dye concentration, catalyst loading, ultrasonic power, and the presence of radical scavengers were investigated.     

The effects of growth conditions on the surface properties and photocatalytic activities of anatase TiO<Subscript>2</Subscript> films prepared via electrochemical anodizing and annealing methods

In the present work, nanostructured TiO₂ films were prepared by electrochemical anodization process of titanium in fluoride-containing electrolytes using an innovative approach. After anodization, the TiO₂ films were annealed at 480?°C for 2 h in air in order to acquire anatase phase transformation and increase its crystallinity. The effects of anodization voltage, electrolyte concentration and anodization time on the formation of TiO₂ films and the photocatalytic degradation of methylene blue (MB) were discussed in details. The phase structure and surface morphology of the samples characterized by means of X-ray diffraction and scanning electron microscope. The as-prepared nanostructured TiO₂ film anodized in 0.5% HF electrolyte at 15 V for 240 min showed excellent photocatalytic degradation of MB and is promising for environmental purification.     

Fabrication of Three-Dimensionally Ordered Macroporous TiO2 Films with Enhanced Photovoltaic Conversion Efficiency

Negative-charged polystyrene (PS) microspheres were prepared through a soap-free emulsion polymerization method using potassium persulfate as initiator. Three-dimensionally ordered macroporous TiO₂ films were fabricated using the high-quality PS colloidal crystals templates obtained via a horizontal deposition method. The as-prepared macroporous TiO₂ films were applied as the photoanodes in dye-sensitized solar cell (DSSC). The microstructure of the products were characterized by X-ray diffractometer, fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy and nitrogen adsorption–desorption analyzer. The results showed that the macroporous TiO₂ films replicated well the 3D ordered structure derived from PS colloidal crystal templates and revealed a relatively large specific surface area (69.99 m²/g), which could increase the capacity of TiO₂ film anode for absorbing dyes and scattering light. The photocurrent–voltage (I–V) characteristics of DSSC were measured by a digital source meter under simulated solar light. The results indicated that the introduction of an ordered macroporous TiO₂ interfacial layer increased the photovoltaic conversion efficiency, which was improved by 68 % from 3.61 to 6.08 %, as compared to a device using a bare P25 TiO₂ photoanode. Our results showed that the hierarchically ordered macroporous TiO₂ bilayer films photoanode for DSSC could be helpful to improve the photovoltaic conversion efficiency.