Papers by Keyword: Niobium Oxide

Abstract: Nb₂O₅ is one of the most favorable transparent conducting oxide materials, which is efficiently used in thin film gas sensors especially for reducing gases. In this research, Al-doped Nb₂O₅ thin films on glass substrates with the DC plasma sputtering method for sensing NH₃ and NO₂ gases. The effect of thermal oxidation time on morphological, structural properties, and gas sensing properties of Nb₂O₅: Al thin films are investigated. Annealing was performed at 450 ° C for two hours. The results of X-ray diffraction (XRD) revealed that the structures are amorphous. Surface topography and growth behavior of Al-doped Nb₂O₅ thin films have an essential role in the optimization of gas sensing properties of these films. Also, atomic force microscopy (AFM) has been used to investigate the surface topography of the obtained films. Obtained results from these analyzes revealed that the films have monoclinic phase and surface topography of Nb₂O₅:Al thin films affected by Al-doped, the roughness and grain size of the surface increased with the increase in the Al content. Also, the effect of Al-doped on the performance of Nb₂O₅ thin films gas sensors is investigated. The results indicated that the best response was Nb₂O₅ film of NH₃ gas and Nb₂O₅:1%Al of NO₂ gas.

Abstract: The development of niobium oxide (Nb₂O₅) thin films is an important work as a result of wide applications of this oxide in the field of material science and thin-film applications. In this study, thin-film microstructures of aluminum (Al)-doped Nb₂O₅ were prepared by DC plasma sputtering on glasses substrate. The ratio of doping was (0.5, 1, and 1.5) wt. % Al. The obtained samples were thermally treated at 450 °C. Characterized and analyzed the physical properties by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), atomic force microscopy (AFM), and UV-Visible spectroscopy for optical properties investigation. Results showed that the average crystalline size of Nb₂O₅:0.5%Al film was found at 26.47 nm and the structure was a monoclinic phase for all samples. The distribution of grain size was found lower than 36.3 nm and uninformed particles on the surface. The analyzed optical properties showed the absorption decreased from 0.46 to 0.05 with increasing the wavelength and Low energy gap values decreased from 3.10 eV for Nb2O5 samples to 2.84 eV for 1.5%Al samples. In general, the doping by aluminum improved the physical properties of Nb₂O₅ films.

Abstract: Pure 8 mol% yttria stabilized zirconia (YSZ) and alumina with 1:4 to form ZTA sample and niobium oxide (Nb₂O₅) as dopant was added to the ZTA system. The samples were sintered at 1650 °C for 2h. The effect of niobium oxide addition as dopant in the ZTA ceramics sample were investigated. It is found that addition of niobium oxide up to 5wt.% had a positive effect on the microstructure and hardness of the ZTA ceramics sample which improve the mechanical properties of the ceramics samples.

Abstract: Transparent niobium oxide thin films were prepared by dc reactive magnetron sputtering under different oxygen flow rate. The niobium oxide thin films have been deposited on silicon wafer and glass substrate from a 99.99% pure niobium target at room temperature. The films were characterized to obtain the relationship between oxygen flow rate and deposition rate, structural, morphology and optical. The result show that the deposition rate decreased with increasing the oxygen flow rate. However, the transmittance spectrum percentage increases with increasing the oxygen flow rate.

Abstract: Aiming at inadequate mechanical properties of Glass ionomer cement (GIC) commonly used in dental clinic, commercial and melt quenched GIC powders as control groups, homemade GIC powder was prepared by sol–gel route and modified by Nb₂O₅. The GIC samples were characterized by X-ray Diffraction (XRD), particle size analysis, Scanning Electron Microscope (SEM) and Fourier Transform Infrared (FT-IR). The compressive strength, Vickers hardness, working and net setting time were tested. The data was analyzed by one-way ANOVA. The XRD results showed that commercial, melt quenched and sol gel GIC powders were similar amorphous. D90 of three GIC powders and Nb₂O₅ powder were 26 μm, 17 μm, 29 μm and 19 μm respectively. 5% Nb₂O₅-GIC exhibited the highest values of compressive strength and Vickers hardness, which were 112.93 Mpa, 139.48 MPa and 142.25 MPa respectively, increased 19.11%, 30.56% and 16.51% (P <0.05); the Vickers hardness were 35.15 MPa, 36.23 MPa and 37.62 MPa, increased 18.03%, 29.95% and 16.32% (P <0.05) compared to those of unmodified GICs as well. There was no significant change of the FT-IR characteristic peaks of modified GIC. The working time of three kinds of GIC were 4'58 ", 3'28" and 4'10 ", the net setting time were 5'16", 3'15 "and 4'38" (standard is 1.5-6 minutes). It was concluded that the dispersion stiffened effect of niobium oxide could improve the mechanical properties of the filling GIC without affecting the clinical operating performance.

Abstract: We explore the unipolar resistance switching effect in sandwich structures based on Nb, Ta and Zr oxide thin films. The structures were fabricated by pulsed laser deposition and low temperature anodic oxidation methods. After electroforming process memory cells demonstrate reproducible switching between low and high resistance states with a resistance ratio around 10². Nonvolatile resistance storage was traced within 40 days. The low-temperature anodic oxidation of Nb was found to be suitable to fabricate flexible nonvolatile memory elements. The parameters of resistive switching are not degraded after 100000 flexing.

Abstract: The goal of this study is to produce and to investigate the mechanical and microstructural properties of composite materials made of hydroxyapatite, obtained from both natural sheep bone and commercial synthetic hydroxyapatite with niobium oxide addition ( 5 and 10 wt%). The samples were subjected to sintering at different temperatures between 1000°C and 1300°C. Microstructures and mechanical properties of sheep hydroxyapatite (SHA) and commercial synthetic hydroxyapatite (CSHA)-niobium oxide composites were investigated. The production of hydroxyapatite (HA) from natural sources is preferred due to economical reason. The aim of development of SHA and CSHA based niobium oxide composites is to improve mechanical properties of HA. The physical and mechanical properties were determined by measuring density, compression strength and Vickers microhardness (HV). Structural characterization was carried out with X-ray diffraction (XRD) and scanning electron microscopy (SEM) studies. In all composites, density values and mechanical properties increased with increasing sintering temperature. The increase of niobium oxide content in all composites showed better mechanical properties. Both of SHA and CSHA composites with at 1300°C sintering temperature showed nearly the same compression strength value.

Abstract: In this paper, the effect of Nb₂O₅ on the microstructure and dielectric properties of BaTiO₃-based ceramics has been investigated. In the study，Nb₂O₅ is added to the BaTiO₃-based ferroelectric material by conventional solid state synthesis. The structure is identified by X-ray diffraction method and SEM is also employed to observe the surface morphologies of the sample. The specimens of the ferroelectric doped with 2wt% Nb₂O₅ sintered at 1260°C for 1h exhibit attractive properties, its dielectric temperature coefficient is lower than 15% over a wide temperature range from －55 to +180°C.

Abstract: Niobium oxide thin films were successfully synthesized starting from niobate nanosheets. The microstructure of as-prepared nanosheets was observed by TEM. The morphology of niobate thin films was investigated by SEM. The phase structure was determined by XRD. The transmittance spectra of as-obtained niobium oxide thin films were measured, and the optical properties were studied. The influences of different thickness on optical properties were also analyzed. As-prepared niobium thin films were treated by being heated at different temperature. The effects of soaking temperature on the structure and optical properties of niobium oxide thin films were discussed in detail.

Abstract: Bioactive ceramics have the ability to chemically bond to bone. This class of biomaterials can be used as coatings on metallic implants, alloplastic bone defect fillers and as scaffold for tissue engineering. The most widely used bioactive ceramics are hydroxyapatite, Ca10(PO4)6(OH)2 and tricalcium phosphate, Ca3(PO4)2. This study presents new bioactive ceramics based on Nb2O5 and Ta2O5. These materials were produced from bioinert ceramics chemically activated by an alkali hydrothermal treatment. Scanning electron microscopy, energy dispersion X-ray spectroscopy and X-ray diffraction analyses on samples incubated in simulated body fluid showed the presence of bone-like apatite, confirming that the modified ceramics surface became bioactive.