Investigation and characterization of radio frequency sputtered Cr1.8Ti0.2O3−δ thin films derived by citrate, sol-gel and solid state routes

Cr_1.8Ti_0.2O_3−δ (CTO) powders were prepared by citrate, sol-gel and solid-state routes, respectively. The effect of preparation methods on the morphology of sputtered thin films was further investigated. X-ray diffraction patterns of the powders and films confirmed a single phase CTO. No impurity was observed even after sintering the powders at 1000 °C for 24 h. X-ray photoelectron spectroscopy analysis showed that Cr 2p (577.8 eV), and O 1 s (531.5 eV) core levels of the sputtered films have ∼1 eV variation in their binding energy positions compared to those of CTO powders. The atomic force microscopy analysis showed the grains of the films obtained by sputtering sol-gel powders had the smallest size in the range of 7-58 nm. The surface roughness of the thin films had the lowest value at 0.70 nm, whereas those obtained from solid state solution had the maximum value of 2.51 nm.     

Growth of MgO thin films with subsequent fabrication of ZnO rods: Structural and photoluminescence properties

We have grown magnesium oxide (MgO) films by the simple evaporation of MgB₂ powders. The subsequent deposition of ZnO by using an atomic layer deposition (ALD) technique generated the ZnO rods on MgO films, realizing the first production of rod-like structures using ALD. We have employed X-ray diffraction, scanning electron microscopy, transmission electron microscopy and photoluminescence (PL) spectroscopy to characterize the samples. PL of MgO films exhibited two emission bands peaked in the blue and blue-green region, respectively. The deposition of ZnO rods changed the shape of the PL spectrum.     

Effect of stabilizer on optical and structural properties of MgO thin films prepared by sol–gel method

The effects of monoethanolamine (MEA) and acetylacetone (ACAC) addition as stabilizer on the crystallization behaviour, morphology and optical properties of magnesium oxide were investigated using thermogravimetry (TG/DTG), X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Visible, photoluminescence (PL) and Fourier transform infrared (FTIR) spectroscopy. Stabilizer addition reduces transparency of the films. MgO films prepared at 500 °C showed weak orientation of (200). However, the films prepared by addition of stabilizer are amorphous. MgO powders were prepared for exhibiting the structural properties. The patterns of MgO powders showed a preferred orientation of (200). The addition of stabilizer causes a reduction in grain size. SEM micrographs show that a homogenous and crack-free film can be prepared at 500 °C and addition of stabilizer causes an increase in packing density.     

Low-temperature sintering behavior of nanocrystalline indium tin oxide prepared from polymer-containing sols

Indium tin hydroxide (ITH) xerogel powders and thin films with different polyvinylpyrrolidone (PVP) contents (0–22%, w/w) were prepared by a classical sol–gel method. To obtain nanocrystalline indium tin oxide (ITO), the ITH xerogels were calcined at 550 °C. The effect of the initial polymer content on the structure of the ITO powders was studied by means of N₂-sorption measurements, small-angle X-ray scattering (SAXS), transmission and scanning electron microscopy. The N₂-sorption measurements revealed that the ITO powders obtained contained micropores and both their porosity and specific surface area decreased with increasing PVP content of the ITH xerogels. The SAXS measurements confirmed the enhanced sintering of the particles in the presence of PVP. The calculated mass fractal dimensions of the ITO powders increased significantly, indicating a significant compaction in structure. The pre-sintered structure could be achieved at relatively low temperature, which induced a significant decreasing (three orders of magnitude) in the electrical resistance of the ITO films.     

Spin-coating derived LSM-SDC films with uniform pore structure

LSM and SDC powders were synthesized by glycine-nitrates technique and LSM-SDC composite porous films are deposited by means of spin-coating process using ethyl cellulose as pore-forming material. According to the surface morphology and microstructure of cathode films identified with scanning electron microscopy (SEM), as the content of ethyl cellulose in slurry was increased, the pore distribution in films becomes more uniform and the pore size is getting smaller. It was found that while the slurry contains 10 wt.% ethyl cellulose and 90 wt.% LSM-SDC composite powders, the cathode film has a fine structure, which has smooth surface without cracks, uniform pore distribution, suitable pore size and three-dimensioned interconnected structure.     

Influences of organic ligands on the microstructure and properties of sol-gel antimony-doped tin oxide thin films

The antimony-doped tin oxide (ATO) thin films were prepared by sol-gel dip-coating process from SnCl2 2H2O and SbCl3 in alcoholic solutions. The influences of organic ligands, including acetic acids (HAc), acetic acids with monoethanolamine (in brief HAc + MEA), and acetic acids with acetylacetone (in brief HAc + AcAc), on the the microstructure and electrical properties of the thin films have been investigated. The thermal behavior of the ATO gels powders and the microstructures of the thin films have been characterized by using thermogravimetric (TG), differential scanning calorimetric (DSC), Fourier transform infra-red spectral (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) analysis. The electrical resistivity of the thin films was detected by four-probe instrument measurement. The thin films with HAc + MEA as coordination ligands had a good crystal quality and showed a preferred orientation along (101) plane when heated at 450 degrees C. As a consequence, it exhibited the best electrical performance. An electrical resistivity of about 6.3 x 10(-3) omega cm could be achieved for the films with 500 nm thickness.     

Electrophoretic deposition of hydroxyapatite

Hydroxyapatite powders were prepared by a chemical precipitation method and electrophoretically deposited on Ti6Al4V surgical alloy substrates. The powders were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), particle size distribution and zeta potential measurements. Prior to electrophoretic deposition, anodic films were obtained on Ti6Al4V and studied by the Auger method. It was established that experimental conditions of powder preparation, electric field and stirring have a significant influence on suspension stability and deposit morphology. The deposition yield was studied at various deposition durations and applied voltages. Sintered coatings were studied by SEM and XRD.     

Properties of conductive films made from fine spherical silver-palladium alloy particles

Silver-palladium alloy films were made by a thick-film technique using several metal powders prepared by the spray-pyrolysis method. Two types of powders were used: silver-palladium alloy powders (15 mol % Pd and 30 mol % Pd) and mixtures of silver and palladium powders. The fired films were about 2–3 m in thickness. The alloy particles sintered uniformly in firing, whereas, in the case of the powder mixtures, the alloying of silver and palladium particles caused uneven particle growth and large voids were formed in the fired films. For this reason the films made from the alloy powders had better conductive properties than those made from the powder mixtures. The resistivities of the films made from the alloy powders were close to the intrinsic value for silver-palladium alloys. Further, the oxidation of palladium during heating in air was significantly suppressed in the alloy powders when the palladium content was lower than 30 mol % in accordance with thermodynamic considerations.     

Behavior of titanium diboride nanofilms and nanopowders in hydrochloric acid solutions

We have studied the behavior of TiB₂ nanofilms and nanopowders in HCl solutions of various concentrations (1.2 to 12.0 mol/L). The TiB₂ films were grown by nonreactive magnetron sputtering in an additional magnetic field or without it. The TiB₂ powder was prepared by reacting fine-particle titanium and boron in a Na₂B₄O₇ ionic melt. The samples were characterized by X-ray diffraction, electron microscopy, energy dispersive X-ray spectroscopy, and atomic force microscopy. The reactions with the acid solutions were studied by atomic absorption spectroscopy. The results demonstrate that a magnetic field applied during the sputtering process improves the corrosion resistance of the films. Titanium diboride powders consisting of rounded particles are shown to have the highest resistance to dissolution in hydrochloric acid.     

Magnetic and Optical Properties of Fe-Doped SnO2 Thin Films Prepared by Electron Beam Evaporation Technique

We have investigated the optical and magnetic properties of Fe-doped SnO₂ thin films that were deposited through a couple of distinct procedures using the electron beam evaporation technique. In the first procedure, which is the common one, each deposition target was prepared by mixing SnO₂ and Fe powders and, in the second one, tin oxide and iron targets were prepared separately. Visible spectrum analysis revealed that the average optical transparency of as-deposited SnO₂:Fe films decreased with Fe-doping level. In addition, the optical transparency of the produced films was improved by annealing. Deposited films were also analyzed by X-ray diffraction, Rutherford backscattering spectrometry, atomic force microscopy, magnetic force microscopy, and phase detection microscopy. It has been revealed that Fe islands have been formed in the films which were produced by the second method. These thin layers also manifested ferromagnetic properties, while those which were deposited by the first procedure were not capable of yielding room-temperature ferromagnetism.     

脉冲激光沉积法制备立方焦绿石结构的Bi1.5ZnNb1.5O7薄膜

采用固相反应法合成具有焦绿石立方结构的Bi1.5ZnNb1.5O7(BZN)陶瓷靶材,采用脉冲激光沉积法在Pt/SiO2/Si(100)基片制备立方BZN薄膜。研究了随衬底温度的变化,薄膜的结晶性能,微观形貌以及介电性能的差异。结果表明当衬底温度在550~650℃时,薄膜具有纯的立方BZN结构,并且在600℃时薄膜的晶粒发育比较完整,此时薄膜具有较高的介电常数和较低的损耗。     

粉末溶胶法制备Pb0.90La0.10Ti0.975O30-3型厚膜的研究

使用溶胶-凝胶法制备了Pb0.90La0.10Ti0.975O3(简称为PLT-1O)粉体，使用XRD及日本SALD-2001型激光散射颗粒度分析仪对粉体进行了分析，结果表明PLT-1O粉体呈钙钛矿结构，一次颗粒细，颗粒尺寸随退火温度的升高而增大。将粉体分散在溶胶中，并采用粉末溶胶法制备了PLT-1O厚膜。利用XRD和SEM对厚膜进行了分析。实验结果表明，适当调控制备工艺技术，利用粉末溶胶法可望制备出符合要求的铁电“厚膜”。     

Morphology and growth of e-beam deposited YSZ thin films

Yttria-stabilized zirconium (YSZ) thin films were grown from the tetragonal phase of ZrO₂ stabilized by 8 wt% of Y₂O₃ (8% of YSZ) ceramic powders using e-beam deposition technique (EB-PVD). The influence of the type of substrate on the microstructure of deposited YSZ thin films was analysed. YSZ thin films (2-3 μm of thickness) were deposited on three different types of substrates: optical quartz (SiO₂), porous Ni-YSZ substrates and Alloy 600 (Fe-Ni-Cr). The dependence of the substrate temperature (from 20 to 600 °C) on the thin film structure and the surface morphology were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was found that (i) the substrate temperature has an influence on the crystallite size, which varied between 12 and 50 nm, (ii) the substrate type has an influence on the growth mechanism of YSZ thin films, and (iii) a bias voltage applied to the substrate during the deposition of thin films has an influence on the densification of YSZ layers.     

Crystal modulation of tungsten oxide gels and films prepared by the sol-gel process using 2,4-pentanedione as an organic ligand

Tungsten oxide gels and films were prepared by the sol-gel process using 2,4-pentanedione (PTN) as an organic ligand. WO₃ powders were obtained by peeling the films from the quartz glass substrates. The crystal structure of both the gels prepared with and without PTN and fired at 700 °C was monoclinic. WO₃ powders peeled from film samples prepared both with and without PTN showed only the monoclinic crystal structure, whereas the crystal phases of both types of films were cubic and a mixture of cubic and monoclinic crystals, respectively. These results indicate that the cubic crystals of the WO₃ in the films were transformed to the monoclinic crystals of the powders after the films were peeled from the quartz glass substrates. It is concluded that the cubic crystals in the films are transformed to stable monoclinic crystals by the peeling process, whereas PTN and the quartz glass substrate can control the crystal phase of WO₃ films selectively to form the cubic structure.     

Perpendicular magnetization in self-assembled films of citrate-capped gamma-Fe2O3 nanocrystals on Si(100) surfaces

gamma-Fe2O3 nanocrystals capped with citrate and octylamine have been chemically prepared. The octylamine-capped nanocrystals exhibit a tendency to form ordered lattices. Films of nanocrystals of varying thickness (454, 720, and 1400 microg/cm2 in the case of citrate-capped nanocrystals and 300 microg/cm2 in the case of octylamine-capped nanocrystals) have been prepared on Si(100) substrates by drop casting and have been characterized by X-ray diffraction, scanning electron microscopy, and atomic force microscopy. Magnetic measurements have been carried out on the films as well as on nanocrystal powders. The films of citrate-capped gamma-Fe2O3 nanocrystals exhibit enhanced perpendicular magnetization, with the anisotropy depending on the film thickness.     

Effect of processing on the particle size of tin oxide nano-powders

Nano sized tin oxide powders have been synthesized via two different chemical routes namely solid-state and sol–gel route for the fabrication of tin oxide gas/odors sensor. The synthesized powders have been characterized by simultaneous thermo gravimetric and differential thermal analysis (TG-DTA), powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and Fourier transform infrared (FTIR) spectroscopy. The effect of synthesis routes have been investigated on particle size and morphology of tin oxide powders. Powder XRD patterns show that the synthesized powders have tetragonal (rutile) crystal structure. FESEM of formed thick films reveal that powder prepared by solid-state reaction route is less agglomerated as compared to the powder prepared by sol–gel route. XRD and FESEM indicate that there is the formation of tin oxide nanoparticles in the range of 15–50 nm. FTIR spectrums of synthesized powders show Sn-O or Sn-O-Sn stretching modes and its lattice modes at 615 and 494 cm^?1.     

Electrocatalytic properties of mechanically alloyed Co-20wt%Ni-10wt%Mo and Co-70wt%Ni-10wt%Mo alloy powders

Mechanically alloyed Co-20wt%Ni-10wt%Mo and Co-70wt%Ni-10wt%Mo (nominal compositions) alloy powders were produced by milling of pure elemental powders. Mechanically alloyed powders were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. MA powder specimens were tested electrollitically in a 30% KOH aqueous solution at 298 K. X-ray diffraction analysis and transmission electron microscopy of milled powders showed the presence of two phases, an fcc solid solution and intermetallic compounds of Ni or Co with Mo. These phases showed a nanometric size. The linear sweep voltammograms confirmed also the presence of two phases in both mechanically alloyed alloy powders. The Co-20wt%Ni-10wt%Mo alloy powders showed the best electrocatalytic activity for hydrogen evolution reaction.     

Magnetic Properties of Fe-Doped Rutile

Ball-milling method was applied to dissolve Fe into titanium dioxide (TiO₂). X-ray diffraction indicated the starting anatase changed to a rutile-type structure with oxygen deficiency after ball milling. Transmission electron microscopy and X-ray absorption experiments were conducted to examine the possible existence of magnetic impurities in the ball-milled powders after they were leached in HCl solutions. Temperature dependence of the resistivity shows semiconducting behavior and the magnetic hysteresis loops at 5 and 300 K exhibit ferromagnetic characteristics. Fe-doped TiO₂ films were also prepared by pulsed laser deposition. The magnetic properties of the films are discussed.     

Synthesis of polymeric titanium and zirconium precursors and preparation of carbide fibres and films

Polymeric precursors for carbothermal reactions were prepared from the chelate derivatives of titanium and zirconium alkoxides L2M(OR)2 (L is an acetylacetonato or ethyl acetoacetato group) in alcohols by reaction with organic compounds having two or more reactive OH groups, such as ethylene glycol, saccharose, tartaric acid or dihydroxybenzenes. These organic groups act as bridging ligands in transesterification and condensation polymerization yielding either spinnable viscous solutions or elastic gels. The rheological properties of the concentrated solutions allowed for the preparation of polymer fibres and films. At temperatures up to 1600 °C, bulk precursors as well as fibres and films were thermally converted into carbide powders, films or coatings. The structural transformations of the polymeric materials into the carbides were investigated using thermogravimetric–differential thermal analyses (TGA–DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infra-red (FTIR) analysis and Raman spectroscopy.     

Effect of temperature on glass-ceramic films prepared by impregnation of commercial float glass surfaces with oxide powders under pressure

SnO₂ samples were prepared as ultrafine powder by a chemical synthesis method and deposited on the surface of commercial float glass substrates. The glass surface was impregnated with these powders under high gas pressure (1.6-1.8 MPa) and heating to below the glass transition temperature in a designed pressurized chamber, forming SnO₂ films on glass surface. Phases were analyzed by X-ray diffraction and the results confirmed the SnO₂ powders as a single-phase tetragonal structure. Analysis of the chemical composition of glass substrates before and after powder impregnation revealed an ion exchange process caused by the substitution of sodium ions by tin ions on the glass surface. Differences in the surface morphology of SnO₂ films on glass surface were related to the morphology of synthesized powders for deposition and impregnation. The mechanism of SnO₂ films on glass surface was based on mass transfer between the glass substrates and SnO₂ powders as a function of the treatment temperature.