Sol–Gel‐Derived Amorphous‐MgNb2O6 Thin Films for Transparent Microelectronics

In this work, transparent amorphous‐MgNb₂O₆ thin films were fabricated on ITO/glass substrates using the sol–gel method. The change in the chemical states, as well as the optical and dielectric properties of MgNb₂O₆ films at various annealing temperatures is investigated. In this study, MgNb₂O₆ films exhibited the amorphous phase when the annealing temperature was below 600°C. From X‐ray photoelectron spectroscopy, the major parts of the films' chemical states can be indexed as Mg²⁺, Nb⁵⁺, Nb⁴⁺, and O^2?. Furthermore, the Nb⁴⁺ element can be reduced at higher annealing temperatures. The average transmission percentage in the visible range (λ = 400–800 nm) is over 80% for all MgNb₂O₆/ITO/glass samples, whereas the optical band gap (E_g) for all samples is estimated at ~4 eV. In addition, the dielectric constant was calculated to be higher than 20 under a 1 MHz AC electric field, with a leakage current density below 2 × 10^?7 A/cm² at 1 V. In this study, the fabrication procedure and experiment results of MgNb₂O₆ films are introduced for transparent microelectronics.     

Dielectric Properties of Sol–Gel‐Derived Bi12SiO20 Thin Films

In this paper the dielectric properties of crack‐free, Bi₁₂SiO₂₀ thin films were investigated. The films were prepared on Pt/TiO₂/SiO₂/Si and corundum substrates using the sol–gel method. The formation of a pure Bi₁₂SiO₂₀ phase was observed at a temperature of 700°C. The Bi₁₂SiO₂₀ thin films, heat treated at 700°C for 1 h, had a dense microstructure with an average roughness (R_a) of 50 nm. The dielectric properties of the film were characterized by using both low‐ and microwave‐frequency measurement techniques. The low‐frequency measurements were conducted with a parallel capacitor configuration. The dielectric constant and dielectric losses were 44 and 7.5 × 10^?3, respectively. The thin‐film dielectric properties at the microwave frequency were measured using the split‐post, dielectric resonator method (15 GHz) and the planar capacitor configuration (1–5 GHz). The dielectric constant and the dielectric losses measured at 15 GHz were 40 and 17 × 10^?3, respectively, while the dielectric constant and the dielectric losses measured with the planar capacitor configuration were 39 and 65 × 10^?3, respectively.     

Intense Red Photoluminescence Emission of Sol–Gel‐Derived Nanocrystalline Mg2TiO4 Thin Films

In this work, undoped Mg₂TiO₄ thin films were fabricated on p‐type Si(111) substrates by the sol–gel method, and the red photoluminescence (PL) of the films is introduced and discussed. According to the experimental results, the red emission appears when the films have been thermally treated at higher temperatures, which have a long range and well‐organized crystalline arrangement. Furthermore, to have better realization of the red emission mechanism of Mg₂TiO₄ films, the optical band gap of Mg₂TiO₄ (E_g^Mg2TiO4) was estimated at ~3.7 eV; furthermore, 325 nm (corresponding energy, hν = 3.82 eV > E_g^Mg2TiO4) and 633 nm (corresponding energy, hν = 1.96 eV < E_g^Mg2TiO4) excited light sources were used to clarify the position of the defect levels. In addition, the influence of annealing atmospheres (O₂, air, and vacuum) on the red emission of our samples is also discussed. A significant variety of red emissions can be found between these annealing conditions: the red emission can be effectively enhanced by O₂ annealing, but weakened by vacuum annealing. Results reveal that the red emission of Mg₂TiO₄ thin films may be highly dependent on the completeness of the O–X–O (X = Mg, Ti) bonds.     

Antimicrobial Activity of Pd‐Doped ZnO Sol‐Gel‐Derived Films

Palladium doped ZnO was prepared by the sol‐gel and dip‐coating techniques, starting with zinc acetate and palladium chloride as precursors, followed by its hydrolysis in methanol. Acetic acid was incorporated to adjust pH, as well as acetylacetonate and monoehtylamine as stabilizers. The sol was later dipped 3 times in silica substrates. Structural, morphological, and antimicrobial properties of the films were investigated for three palladium contents (1.0, 2.5, and 5 mol %). X‐ray diffraction (XRD) showed that the films have a hexagonal structure after been annealed at 500°C. X‐ray photoelectron Spectroscope (XPS) showed that Pd is present in its oxidized form. Atomic force microscopy (AFM) from films showed a crack free and smooth surface (Ra= 18 nm), composed of cross‐linked particles. The synthesized films presented antibacterial activity against Escherichia coli and Pseudomona aeruginosa. It was observed that the higher Pd content (5 mol %) presents the higher antimicrobial ratio, 64.07%, for the E. coli, whereas for the P. aeruginosa, the lower Pd content (1 mol %), shows the higher antimicrobial ratio, 76.43%.     

Resistive Switching Behaviors of Sol‐Gel‐Derived MgNb2O6 Thin Films on ITO/glass Substrate

In this study, transparent amorphous MgNb₂O₆ (MNO) films were fabricated via the sol‐gel method to form an Al/MNO/indium tin oxide/glass structure. The resistive switching (RS) behavior of the devices was investigated. From the DC voltage sweep test, the air‐annealed MNO samples exhibited stable and reproducible bipolar resistive switching (BRS) behavior; however, the samples annealed in an O₂‐rich environment showed no RS property. These results suggest that the RS behavior of the MNO memory devices is highly related to the oxygen vacancy concentration and distribution within the MNO films. In addition, forming‐free unipolar resistive switching (URS) behavior was observed when the MNO films were annealed under an N₂H₂ atmosphere. In order to determine the origin of the BRS and URS behaviors, cross‐sectional high‐resolution transmission electron microscopy images of the MNO samples were acquired. The RS behavior of the MNO films can be ascribed to the release and recombination of electrons and oxygen vacancies.     

Hydrogen Permeation Properties and Hydrothermal Stability of Sol–Gel‐Derived Amorphous Silica Membranes Fabricated at High Temperatures

The sol–gel method was applied to the fabrication of amorphous silica membranes for use in hydrogen separation at high temperatures. The effects of fabrication temperature on the hydrogen permeation properties and the hydrothermal stability of amorphous silica membranes were evaluated. A thin continuous silica separation layer (thickness = <300 nm) was successfully formed on the top of a deposited colloidal silica layer in a porous glass support. After heat treatment at 800°C for an amorphous silica membrane fabricated at 550°C, however, it was quite difficult to distinguish the active separation layer from the deposited colloidal silica layer in a porous glass support, due to the adhesion of colloidal silica caused by sintering at high temperatures. The amorphous silica membranes fabricated at 700°C were relatively stable under steam atmosphere (500°C, steam = 70 kPa), and showed steady He and H₂ permeance values of 4.0 × 10^?7 and 1.0 × 10^?7 mol·m^?2·s^?1·Pa^?1 with H₂/CH₄ and H₂/H₂O permeance ratios of ~110 and 22, respectively. The permeance ratios of H₂/H₂O for membranes fired at 700°C increased drastically over the range of He/H₂ permeance ratios by factors of ~3–4, and showed a value of ~30, which was higher than those fired at 500°C. Less permeation of water vapor through amorphous silica membranes fabricated at high temperatures can be ascribed to the dense amorphous silica structure caused by the condensation reaction of silanol groups.     

Al-Sc共掺杂ZnO透明导电薄膜的掺杂机制

采用溶胶-凝胶法制备Al-Sc共掺杂ZnO透明导电薄膜,考察了结晶性、晶界状态、紫外-可见光透射光谱及Hall效应,并讨论其掺杂机制,结果表明:Sc单独掺杂时,晶粒尺寸变小,结晶性变差,晶粒表面包裹一层非晶相,透射光谱存在较大的吸收谷,无导电性;Al-Sc共掺杂时,晶粒表面无非晶相,c轴择优取向性和晶界状态变优,透射光...     

Sol‐Gel‐Derived Sb‐Doped SnO2 Nanoparticles Controlled in Size by Nb2O5

Nanocrystalline Sb‐doped SnO₂ particles were prepared by sol‐gel and their particle growth was controlled by niobium oxide. In the present synthesis, SnCl₄ and SbCl₃, as precursors, were dissolved and hydrolyzed in ethylene glycol at 80–120 °C, and further 0.1 mol.‐% Nb₂O₅ through its precursor NbCl₅ was mixed to the above solution. The mixture was then dried at 120–150 °C and calcinated at 600 °C for 2 hours. By XRD and TEM, Sb‐doped SnO₂ nanoparticles were highly crystalline and their mean crystal size was ca.10–20 nm with narrow particle size distribution. As the addition of antimony increased, the crystallinity and particle size distribution of SnO₂ particles had the trend to decrease.     

超声喷雾热分解法制备硅薄膜太阳电池用ZnO：In透明导电膜

采用超声喷雾热分解法,在Eagle2000衬底上制备ZnO薄膜。通过Hall测试、X射线衍射、扫描电子显微镜和透过率测试研究不同In掺量对ZnO薄膜电学、结构、表面形貌和光学特性的影响。结果表明：当In摩尔掺量（In与ZnO的摩尔比）为1.5%时,获得的薄膜具有较低的电阻率（2.48×10–3cm）;所有In掺杂ZnO...     

A Unique Approach to Characterization of Sol‐Gel‐Derived Rare‐Earth‐Doped Oxyfluoride Glass‐Ceramics

Using the sol‐gel route Nd³⁺‐doped oxyfluoride glass‐ceramics were prepared. LiYF₄ and YF₃ crystals were deposited in the glass‐ceramics and their size, distribution, and amount ratio were varied by changing the compositions and heating temperatures. The incorporation of Nd³⁺ ions into both the fluoride crystals was confirmed by the high‐resolution elemental mapping of the glass‐ceramics. The incorporated Nd³⁺ ions showed up and down conversion photoluminescence whose properties were obviously different among the samples. The preliminary site analysis for Nd³⁺ ions was carried out using a unique approach associated with the Prony series approximation. Finally, the approach was found to be useful for the analysis of materials that are structurally complicating.     

Acid Corrosion Behavior of Sol–Gel‐Prepared Mullite Ceramics With and Without Addition of Lanthanum

The corrosion behavior of pure and lanthanum doped, sol – gel‐derived, mullite ceramics in nitric acid aqueous solutions with various concentrations was investigated and compared. Samples sintered at a temperature of 1600°C for 4 h were characterized using powder X‐ray diffraction, SEM, and energy dispersive X‐ray spectroscopy. The corrosion behavior was explored by measuring the amount of eluted ions using atomic absorption spectrophotometry and inductively coupled plasma optical emission spectrometry (ICP‐OES). The doped sample was found to be more susceptible to dissolution in the corrodent, having higher leaching rates. The amounts of eluted lanthanum ions were in order of magnitude higher than amounts of silicon and aluminum. Those phenomena were attributed to the incorporation of lanthanum in the glassy phase, forming SiO₂ – La₂O₃‐rich glassy phase, which can dissolve in corrodent more easily than SiO₂‐rich glassy phase in the pure sample.     

Effective Air‐Spray Deposition of Thin Films Obtained by Sol–Gel Process onto Complex Pieces of Sanitary Ware

A deposition mechanism by air‐spray technique is carried out for depositing silica‐based thin films obtained by the sol–gel process. The air‐spray deposition is very useful to coat large and complex surfaces with different morphologies and roughnesses which favors the technology scale‐up, contrary to the most used deposition methods in the sol–gel process (dip and spin coating). To establish the adequate conditions of these techniques, a complete study of the sol properties (rheology, FT‐IR, roughness, thickness) is attempted, which has allowed determining the parameters for the effective air‐spray deposition of homogeneous thin films. By means of an experimental design, it has been possible to validate the selected parameters. Finally, a scheme of an effective spray deposition model is proposed for a better understanding of the deposition mechanisms.     

A Comparative Study of Densification of Sol‐Gel‐Derived Nano‐Mullite due to the Influence of Iron,Nickel and Copper Ions

By sol‐gel process, mullite samples doped with 0.002M, 0.02M, 0.1M, 0.15M, and 0.2M of iron, nickel, and copper are prepared. Prepared gels were then dried, grinded, pressed into pellets, and sintered at temperatures 1000°C and 1300°C for 4 h. Mullite densification behavior was analyzed. Our intention is to study the role of metal ions in influencing mullitization behavior in the case of the sol‐gel reaction process, to provide useful information of mullite. This study deals with the effect of metal ions on mullite formation, microstructure, and densification behavior in single‐phase sol‐gel‐derived mullite.     

Sol–Gel Synthesis and Characterization of Na0.5Bi0.5TiO3–NaTaO3Thin Films

Thin films with the composition 70 mol% Na_0.5Bi_0.5TiO₃ + 30 mol% NaTaO₃ were prepared by sol–gel synthesis and spin coating. The influence of the annealing temperature on the microstructural development and its further influence on the dielectric properties in the low‐ (kHz–MHz) and microwave‐frequency (15 GHz) ranges were investigated. In the low‐frequency range we observed that with an increasing annealing temperature from 550°C to 650°C the average grain size increased from 90 to 170 nm, which led to an increase in the dielectric permittivity from 130 to 240. The temperature‐stable dielectric properties were measured for thin films annealed at 650°C in the temperature range between ?25°C and 150°C. The thin films deposited on corundum substrates had a lower average grain size than those on Si/SiO₂/TiO₂/Pt substrates. The highest average grain size of 130 nm was obtained for a thin film annealed at 600°C, which displayed a dielectric permittivity of 130, measured at 15 GHz.     

High‐Performance Nanocomposites of Sodium Carboxymethylcellulose and Graphene Oxide

High‐performance nanocomposites of NaCMC with GO are produced by solution casting. FESEM images reveal a good homogeneous dispersion of GO in the NaCMC matrix. The composite formation is facilitated by H‐bonding interaction between GO and NaCMC. T_g of the composites increases with increasing GO concentration. The storage modulus (G′) exhibits a maximum 174% increase over NaCMC at 1 wt% GO. The mechanical properties of the composites exhibit highest increase of tensile stress and Young's modulus of 188 ± 4% and 154 ± 11%, respectively, for 1 wt% GO. Analysis of Young's modulus (E_y) data using the Halpin‐Tsai equation suggests that the E_y data are close to the unidirectional orientation at >0.5 wt% GO, indicating more efficient load transfer at these compositions.

     

Sol-Gel Preparation of Transparent and Conductive Aluminum-Doped Zinc Oxide Films with Highly Preferential Crystal Orientation

Transparent aluminum-doped zinc oxide (ZnO) films were prepared via the sol-gel method on silica-glass substrates from 2-methoxyethanol solutions of zinc acetate and aluminum chloride that contained monoethanolamine. Dip coating was conducted at room temperature, with substrate withdrawal rates of 1.2-7.0 cm/min. After each deposition, the films were heat-treated in air at 200°-450°C for 10 min (pre-heat-treatment). After six to fourteen layers had been deposited, the films were then subjected to annealing in air at 500°-800°C for 1 h (the first post-heat-treatment), followed by annealing in nitrogen at 500°-700°C for 15 min to 4 h (the second post-heat-treatment). All the films obtained were transparent and showed only an extremely sharp ZnO (002) peak in the X-ray diffractometry (XRD) patterns. The effects of the aluminum content, the substrate withdrawal speed, and the heat-treatment conditions on the electrical resistivity of the films were studied. All these factors strongly affected the resistivity. The lowest resistivity value (6.5 10^-3 Omegacm) was achieved in a film that contained 0.5 at.% aluminum, prepared with a low substrate withdrawal speed (1.2 cm/min), and a pre-heat-treatment of individual layer at 400°C in air and a post-heat-treatment of the entire film at 600°C in air, followed by a post-heat-treatment at 600°C in nitrogen. These preparation parameters also affected the degree of crystal orientation, which was revealed by the intensity of the ZnO (002) XRD peak. Higher crystal orientation was effective in reducing the film resistivity, whereas the higher grain-packing density and possible aluminum segregation were thought to have positive and negative effects, respectively, in reducing the resistivity.     

Synthesis,Characterization, and In Vitro Bioactivity of Sol‐Gel‐Derived Zn,Mg, and Zn‐Mg Co‐Doped Bioactive Glasses

Bioactive glasses in the systems CaO‐SiO₂‐P₂O₅‐ZnO, CaO‐SiO₂‐P₂O₅‐MgO, and CaO‐SiO₂‐P₂O₅‐MgO‐ZnO were prepared and characterized. Bioactive glass powders were produced by the sol‐gel method. The prepared bioactive glass powders were immersed in a simulated body fluid (SBF) for periods of up to 28 days at 310 K to investigate the bioactivity of the produced samples. Inductively coupled plasma (ICP) and ultraviolet (UV) spectroscopic techniques were used to detect changes in the SBF composition. X‐Ray diffraction (XRD) was utilized to recognize and confirm the formation of a hydroxyapatite (HA) layer on the bioactive glass powders. Microstructural characterizations of the bioactive glass samples were investigated by scanning electron microscopy (SEM) techniques. Density, porosity, and surface area values of bioactive glass powders were also determined in order to characterize the textural properties of the samples. The results revealed the growth of an HA layer on the surface of the bioactive glass samples. MgO in the glass sample increases the rate of formation of an HA layer while ZnO in the glass slows it down.