The Effect of the Multi-doping Strategy on Stabilization of the Cubic δ-phase in the Bi2O3-based Solid Electrolyte Systems in Terms of the SOFC Applications

In this study, the effects of multi-doping strategy on phase stabilization and electrical conductivity for the doped Bi 2 O 3 system were investigated. All solid mixtures were created by solid state reactions according to a certain stoichiometric ratio in atmospheric conditions. The structural, electrical, thermal and surface characterizations of the created samples were performed by x-ray diffraction method (XRD), four point-probe technique (4-PPT), differential thermal analysis/thermo gravimetric analysis (DTA/TGA) and scanning electron microscope (SEM), respectively. From XRD results, it was seen that the fcc δ-phase could be stabilized by using only 1:1:1:2 or 2:2:2:1 dopant content ratio (in here, “1:” is corresponds to” 5%” mole). The other compounds prepared out of this ratios were mixed phase because of the containing both α-phase peaks and δ-phase peaks on their XRD pattern. When the all samples were compared in terms of electrical conductivity at 750 °C, it was observed that the fcc δ-phase stabilized samples exhibited higher conductivity than that of other compounds as expected. The highest electrical conductivity was for the sample, dopant content ratios of which are 1: 1: 1: 2, with 0.014 S.cm -1 at 750 °C and also it had the lowest activation energy (0.51 eV) among all samples. On the other hand, according to the thermal analysis results, it was concluded that phase transition occurred only on the DTA curve of the sample given with dopant content ratios 1:1:1:1 due to presence of endothermic peak on its DTA curve at 729°C during the heating process. Also, for this sample, it was clearly predicted from the electrical conductivity graphs depending on temperature that the phase transition occurred at just that temperature (729 °C) due to the sudden increase in conductivity by indicating phase transition from the α-phase to the cubic δ-phase. The SEM analysis pointed out that grain size decreased as total dopant ratio increased and also the grain boundary changed sharply with the increase in the total dopant ratio.

Sol-Gel Combustion Synthesis, Crystal Structure and Luminescence of Cr3+ and Mn4+ Ions in Nanocrystalline SrAl4O7

A series of strontium dialuminate SrAl4O7 nanopowders with the grossite-type structure doped with chromium and manganese ions were synthesized by the combined sol–gel solution combustion method with use of two different strontium salts. The Cr3+ and Mn4+ ions concentrations were varied from 0.05 to 5 at.%. Evolution of phase composition, crystal structure, and microstructural parameters of the nanocrystalline materials depending on the synthesis conditions, temperature of thermal treatment, and dopant content were investigated by the X-ray powder diffraction and the scanning electron microscopy techniques. Photoluminescent properties of SrAl4O7 nanophosphors activated with Cr3+ and Mn4+ ions were studied at room temperature. The samples exhibit typical photoluminescence in the deep-red spectral region, corresponding to d-d transitions in Cr3+ or Mn4+ ions. The intensity of this deep-red emission is dependent on the dopant concentration and annealing temperature. Features of the formation of octahedral surroundings around Cr3+ or Mn4+ ions are discussed.

Effect of Sr Doping on Structural and Transport Properties of Bi2Te3

Search for doped superconducting topological insulators is of prime importance for new quantum technologies. We report on fabrication of Sr-doped Bi2Te3 single crystals. We found that Bridgman grown samples have p-type conductivity in the low 1019 cm−3, high mobility of 4000 cm2V−1s−1, crystal structure independent on nominal dopant content, and no signs of superconductivity. We also studied molecular beam epitaxy grown SrxBi2−xTe3 films on lattice matched (1 1 1) BaF2 polar surface. Contrary to the bulk crystals thin films have n-type conductivity. Carrier concentration, mobility and c-lattice constant demonstrate pronounced dependence on Sr concentration x. Variation of the parameters did not lead to superconductivity. We revealed, that transport and structural parameters are governed by Sr dopants incorporation in randomly inserted Bi bilayers into the parent matrix. Thus, our data shed light on the structural position of dopant in Bi2Te3 and should be helpful for further design of topological insulator-based superconductors.

Preparation Protocol and Properties of YSZ Ceramic Electrolytes for Solid Oxide Cells

Electrolytes utilized in solid oxide cells (SOCs) are based on oxide ion-conductive ceramic materials. The conductivity occurs via oxygen vacancies in the crystal lattice, which are created by the introduction of dopant into the material. Fast and simple preparation of electrolytes using variable dopant content is of great importance for SOCs development. ZrO2 doped by Y2O3 (YSZ) is still considered to be a state-of-the-art material due to its conductivity and thermomechanical compatibility with electrodes. Therefore, a detailed procedure to fabricate YSZ electrolytes with desired dopant content is of significant importance. Each prepared electrolyte was examined by means of spectroscopic methods in combination with electrochemical ones. The results obtained allows to understand connection between electrolyte composition and structural properties.

Optical Properties of Non-Crystalline Fluorine Doped Hematite Fe2O3 Thin Films Deposited by Chemical Spray Pyrolysis Technique

By using the spray pyrolysis technique, un-doped and Fluorine highly doped iron oxide Fe2O3 thin films were deposited on a glass substrate at a temperature of 380 oC and at different dopant concentrations (10, 15, and 20) %. The crystal structure and optical characterization of the deposited thin film were performed by x-ray diffraction and UV-Vis spectrophotometer. The XRD results revealed that the presence of a very wide peak in-between (15-35) o angles, this gives evidence that un-doped and F-doped Fe2O3 thin films have very low crystallinity and amorphous structures. The optical absorbance edge was shifted towards short wavelengths (blue shift) and the absorbance was reduced with the increase of Fluorine dopant content. The optical constants such as absorption, extinction coefficients, and the optical conductivity of the deposition films were investigated as a function of dopant content. The optical energy band gap of un-doped and Fe2O3:F thin films was found to be increased when increasing of the Fluorine content and exhibited a direct allowed energy gap (Eg) from (2.55 to 2.7) eV which can related to the Burstein-Moss effect.

The Effects of Manganese Dopant Content and Calcination Temperature on Properties of Titania-Zirconia Composite

The effects of dopant content and calcination temperature on Mn-doped TiO2-ZrO2 structure and properties were successfully investigated. Composite of Mn-doped titania-zirconia was synthesized by sol-gel method. Titanium(IV) isopropoxide was used as the precursor of TiO2, while zirconiapowder was used as another semiconductor. MnCl2∙4H2O was used as the source of dopant in this study. Various amounts of manganese were incorporated into TiO2-ZrO2 and calcination was performed at temperatures of 500, 700 and 900 °C. Synthesized composites were characterized by Fourier-transform infrared spectroscopy (FTIR), specular reflectance UV-Vis spectroscopy (SR UV-Vis), X-ray diffraction method (XRD) and scanning electron microscopy equipped with X-ray energy dispersive spectroscopy (SEM-EDX). The results showed that Mn-doped TiO2-ZrO2 with the lowest bandgap (2.78 eV) was achieved with 5% of Mn dopant and calcined at 900 °C, while Mn-doped TiO2-ZrO2 with the highest bandgap (3.12 eV) was achieved with 1% of Mn dopant content calcined at 500 °C.

Effect of heteroatoms on the optical properties and enzymatic activity of N-doped carbon dots

The characteristics of N-CDs suitable for their optical applications or for use as nanozymes were demonstrated by rationalizing the relationship between the dopant content (e.g., the amount of doped N and types of chemical bonding) and physicochemical properties.

Fast oxide-ion conductors in Bi2O3-V2O5 system: Bi108-xVxO162+x(x=4-9) with 3×3×3 superstructure

In this study, the possibility to stabilize O2-ion conductors in Bi2O3-V2O5 system was investigated. Six pseudo-binary Bi2O3-V2O5 mixtures [3.50 < x(V2O5) < 8.50 mol%] were thermally treated at 1000?C for 1 h. The samples were characterized by XRD, HRTEM/SAED, DTA and EIS techniques. The high-temperature reaction between ? Bi2O3 and V2O5 resulted in formation of microcrystalline single-phase specimens containing the phase based on ?-Bi2O3 if V2O5 content was ? 4.63 mol%. The obtained phases exhibited main diffraction peaks corresponding to the simple cubic ?-Bi2O3 (space group Fm-3m) but Rietveld refinement showed a threefold repeat on a simple cubic sublattice indicating that the true unit cell is 3?3?3 supercell. Within proposed supercell, the octahedrally coordinated V5+ ions fully occupy 4a Wyckoff position and partially occupy 32f. The Bi3+ ions are placed at the rest of 32f and at 24e and 48h with full occupation. In total, 22 % of anionic sites are vacant. The ionic conductivity of phase with the lowest dopant content, i.e. Bi 103V5O167, amounts 0.283 S cm-1 at 800?C with the activation energy of 0.64(5) eV, which is comparable to the undoped ?-Bi2O3 known as the fastest ion conductor.