Nb-doped TiO2 Thin Films Prepared through TiCl4 Treatment for Improvement of Their Carrier Transport Property

ABSTRACTNb-doped TiO2 thin-films were prepared on fluorine-doped tin oxide (FTO) coated glass directly with niobium ethoxide and TiCl4 in water under the acidic conditions with several concentrations of HCl at 70-90 °C for 45 minutes or 1 hour followed by rinsing with water and annealing at 100 °C for 1 hour. Thin films of 0-1% Nb-doped TiO2 with rutile phase on FTO were obtained, which were confirmed through X-ray diffraction analyses and measurements of energy dispersive X-ray spectroscopy (EDS). Scanning electron microscopy observations equipped with EDS revealed that higher growth temperature over 90 °C is required for doping of Nb. While higher concentration of HCl resulted in much amount of Nb-doping. Band gap of rutile TiO2 gradually reduced from 3.3 eV to 3.23 eV through Nb-doping from 0% to 1%, which were estimated from uv-vis absorption spectroscopic analyses. Hall effect measurements by taking van der Pauw method confirmed that 2.26 times increase of the carrier density and 1.78 times enhancement of the conductivity have been achieved in the case of 1% Nb-doping.

Dielectric properties of the PFN ceramics obtained different chemical-wet technology and sintering by hot pressing method

The paper shows three kinds of chemical-wet technology synthesis of the ferroelectric-ferrimagnetic PbFe1/2Nb1/2O3 materials and technology process of the ceramic samples sintered by hot pressing method. In the technological process of the PFN powders were used follows precursors: lead acetate trihydrate and niobium ethoxide while an iron-related components were changed: iron nitrate obtained by first sol-gel technology (PFN-n), iron oxalate obtained by second sol-gel technology (PFN-ox) and iron citrate obtained by third technology (PFN-c). XRD, SEM tests and temperature measurements of dielectric properties of the ceramic samples were carried out. The SEM microstructure tests of the PFN ceramic samples confirm the properly conducted technological processes. The best dielectric properties of the PFN ceramic samples were obtained for third technology using iron citrate precursor. But, this method of the PFN ceramic powder requires minimization of a pyrochlore phase and reduction porosity of the ceramic samples.

Enhanced photocatalytic hydrogen evolution from water by niobate single molecular sheets and ensembles

We report single molecular sheets of niobate prepared by a simple bottom-up approach using hydrothermal synthesis of niobium ethoxide with the aid of triethanolamine as a structural modifier.

Synthesis of a KNbO3 particle/polymer hybrid from metalorganics

A nanocrystalline KNbO3 particle/polymer hybrid was synthesized through controlled hydrolysis and polymerization of metalorganics below 100 °C. A KNbO3 precursor was synthesized from potassium ethoxide, niobium ethoxide, and acetoacetoxyethyl methacrylate. The K–Nb alkoxide precursor was hydrolyzed and polymerized yielding KNbO3 particle/polymer hybrid. The organic matrix included nanometer-sized crystalline particles depending upon the hydrolysis conditions. The nanocrystalline particles were identified to be potassium niobate by electron diffraction and energy dispersive x-ray analysis. The suspension of the hybrid in silicone oil revealed a yield stress dependent upon various conditions, such as concentration and applied field. The hybridization was found to have a pronounced effect on the electrorheological properties of the fluid, including the KNbO3 particle/polymer hybrid.

A novel route for the synthesis of Sr1−xBaxNb2O6 thin films

Stoichiometric Sr1−xBaxNb2O6 (SBN) powder and thin films were prepared by a chemical method. The starting materials were niobium ethoxide and the hydroxides of strontium and barium. Powders were obtained by evaporation of the precursor solution, and thin films were deposited by spin coating. Annealing temperature required to obtain complete conversion to the crystalline material was about 700 °C. Stoichiometric polycrystalline films of Sr1−xBaxNb2O6 were deposited on quartz and silicon substrates. Leakage current-voltage and the capacitance-voltage measurements on a metal/SBN/n-silicon structure show a diode-type characteristic.

Fabrication of Sr2Nb2O7 thin films by sol-gel processing

Sol-gel Sr2Nb2O7 thin films were deposited on Si(100) and Pt-coated Si substrates for the first time by spin-coating. The Sr2Nb2O7 precursor solution was prepared from strontium metal dissolved in 2-methoxyethanol, acetylacetone, and niobium ethoxide. The formation of phase pure Sr2Nb2O7 occurred via an intermediate perovskite phase of composition close to Sr0.82NbO3. Crack-free Sr2Nb2O7 films of ∼0.4 μm thickness were deposited on these substrates using a single-coating followed by heat treatment at 850 °C for 12 h. SEM microstructure and thin film XRD results indicated the deposition of a grain-oriented film on the Pt-coated Si substrate. The room temperature dielectric constant and the loss values of the film measured at 10 kHz are 45 and 0.045, respectively.