Papers by Keyword: Praseodymium

Abstract: Praseodymium (Pr) doped (0.1 to 6 wt. %) nanostructured SnO₂ thin films are prepared via nebulizer assisted spray deposition process at a deposition temperature of 320 °C. The analyses show that the films grow in (110), (301) and (310) preferred orientations. The fabricated sensing films are exposed to LPG at 500 ppm concentration and at different operating temperatures. In 500 ppm of LPG, at an operating temperature of 350 °C, a commendable sensor response of 99 % with fast response time of 9 s and recovery time of 11 s is shown by 1wt.% Pr doped film, which is appreciable compared to pristine SnO₂ film. The sensor response reduces at lower operating temperatures. Microstructural investigations justify the gas sensing performance of 1 wt.% Pr doped SnO₂ thin film. Raman and photoluminescence studies give an insight into oxygen vacancies and trapped states that have a crucial influence on gas sensing.

Abstract: Nd₂Fe₁₄B permanent magnet manufacturing technology in some developing countries is still relatively difficult because it is constrained by limited equipment facilities and dependence on imports of raw materials. In the context of efforts to build national independence, the concrete step is to try to study the process of making permanent Nd₂Fe₁₄B magnets with conventional facilities and technology. In this research an attempt was made to make and characterize Nd₂Fe₁₄B permanent magnets substituted with praseodymium Pr metal using conventional technology through the arc melting method. The success parameter of the results of this sample making is the formation of the Nd₂Fe₁₄B phase in the sample. The formation of this phase can be fundamentally studied the number of mass fractions of formed phases and structure crystallography using X-ray diffraction facilities and is supported by spectroscopy facilities and their magnetic properties. So the purpose of this research in general is to study the manufacturing process and the fundamental formation of the phases of the NdPrFe₁₄B sample making through the arc melting method, while specifically wanting to know the relationship between phase analysis and the magnetic anisotropic properties of NdPrFe₁₄B. The coercivity field appears to increase significantly after the sample is substituted with Pr and has a fairly small crystallite size distribution. So it was concluded that the presence of Pr was able to withstand the growth of grain, causing the anisotropic magnetocrystalline field to increase.

Abstract: La₂Ti₂O₇:Pr powder was prepared by a solid-state reaction method. Photoluminescence due to f-f transitions of Pr³⁺ was induced by band-gap excitation of La₂Ti₂O₇. La₂Ti₂O₇:Pr thin film was prepared by sol-gel and spin-coating methods. The thin film showed visible electroluminescence due to f-f transition of Pr³⁺ by applying ac voltages.

Abstract: The aim of this work was to obtain Pb_0.92(La_0.08)(Zr_0.65Ti_0.35)_0.98O₃ materials co-doped with two different lanthanide ions (Ln³⁺) and characterization how they influence on the physical properties of prepared 8/65/35 PLZT: Ln³⁺ ceramics. As a co-dopant, praseodymium (Pr³⁺) and neodymium (Nd³⁺) ions were used at the concentration of 0.0 and 0.5 wt.% respectively. The ceramic powders of 8/65/35 PLZT, PLZT:Pr³⁺ as well PLZT:Nd³⁺ were synthesized by conventional ceramic route, from high purity raw oxide materials (>99,9%). All compositions of the ceramic samples were sintered via single time process at T_s=1200°C/3h, by the hot uniaxial pressing method. Performed measurements have shown dependence of used dopant on structure, microstructure, and dielectric as well optical properties of the fabricated 8/65/35 PLZT: Ln³⁺ materials.

Abstract: Oxide inorganic electroluminescent device in which thin films of Pr-doped NaNbO₃ phosphor and Sb-doped SnO₂ transparent conductor are alternately stacked was prepared by sol-gel and spin-coating methods. Red electroluminescence was observed due to f-f transitions of Pr³⁺ ions by applying 5-kHz ac voltages to the device. The luminance was 1.0 cd m⁻² at 25 V ac and5.0 cd m⁻² at 34 V ac.

Abstract: Pr doped SnO₂ particles as negative electrode material of lithium-ion battery are synthesized by the coprecipitation method with SnCl₄·5H₂O and Pr₂O₃ as raw materials. The structure of the SnO₂ particles and Pr doped SnO₂ particles are investigated respectively by XRD analysis. Doping is achieved well by coprecipitation method and is recognized as replacement doping or caulking doping. Electrochemical properties of the SnO₂ particles and Pr doped SnO₂ particles are tested by charge-discharge and cycle voltammogram experimentation, respectively. The initial specific discharge capacity of Pr doped SnO₂ the negative electrode materials is 676.3mAh/g. After 20 cycles, the capacity retention ratio is 90.5%. The reversible capacity of Pr doped SnO₂ negative electrode material higher than the reversible capacity of SnO₂ negative electrode material. Pr doped SnO₂ particles has good lithiumion intercalation/deintercalation performance.

Abstract: Visible luminescence of Pr³⁺ ions in bismuth borate glasses doped with difference concentration of Pr₂O₃ have been studies. The glasses of composition 30Bi₂O₃ : (70-x)B₂O₃ : xPr₂O₃ (where x = 0.0, 0.5, 1.0, 1.5, 2.0 and 2.5 mol%) were prepared by the melt quenching technique. The spectral properties were investigated using the absorption and emission measurement. These glasses have shown emission and excitation bands in visible region. The emission band of Pr³⁺ doped glass centered at 600 nm (¹D₂ ³H₄), 642 nm (³P₀ ³F₂) and 704 nm (³P₀ ³F₃) have been observed with 469 nm (³H₄ ³P₁) excitation wavelength. The excitation band revealed centered at 447, 469 and 482 nm corresponding to the ³H₄ ³P₂, ³P₁ and ³P₀ transitions, respectively.

Abstract: Powder of Pr-doped CaTiO₃ red phosphor was prepared at 1473 K by a conventional solid-state reaction method with addition of B₂O₃ or SiO₂ as a flux. Primary particle sizes of the prepared samples were increased by using B₂O₃ flux but decreased by using SiO₂ flux. Clear planes, edges, or steps were observed on surfaces of the primary particles. The intensity of photoluminescence induced by irradiation of light with a wavelength longer than ∼350 nm was enhanced about three times by using B₂O₃ flux. The intensity of photoluminescence induced by irradiation of light with a wavelength shorter than ∼350 nm was enhanced about twice by using either B₂O₃ or SiO₂ fluxes. The origin for the flux effects is discussed.

Abstract: Praseodymium salt was used as additives for the first time in preparing anodic aluminum oxide (AAO) films to improve its performance. AAO films were prepared by anodization method from a 15 vol.% sulphuric acid solution containing praseodymium salt. The effects of Pr concentration on microhardness and thickness of AAO film were investigated, respectively. The effect of heat treatment temperature on structure of AAO film was investigated. AAO films were characterized by XRD, EDAX and SEM techniques. AAO films showed higher microhardness and thickness, the surface of AAO film was smoother and the aperture of AAO film was more uniform than those of films prepared in 15 vol. % sulphuric acid anodization solution. The microhardness and thickness of AAO film were 355.7HV and 84μm respectively. The apertures of AAO film were in 25～30nm. There was not praseodymium in AAO film. AAO films were amorphous when heat treatment temperatures of AAO film were below 800°C. When heat treatment temperature of AAO film were 850°C and 1000°C respectively, AAO films were γ-Al2O3 and α-Al2O3 film respectively.

Abstract: Lanthanum Nickelate (LaNiO₃) and Praseodymium (Pr) substituted compounds were prepared by molten flux method using chloride precursors. The investigation presents the characterization of the synthesized materials using TGA/DTA, XRD, FTIR, CHNS, EDAX, UV-visible, EPR spectral and SEM studies. The thermo gravimetric analysis reveals the decomposition and thermal reactions of the precursors at different temperature regions. The XRD analysis shows that the synthesized crystals have the rhombohedral structure. FTIR spectra exhibit the absorption bands for the O-H stretching vibration and Ni-O bands at different wave lengths. A shift in band position has been observed on the substitution of Pr³⁺ ions in the parent compound. The CHNS analysis presents the impurities level in the synthesized compounds. The EDAX analysis shows the concentration of La, Ni, Pr and O in the synthesized compounds. The band gap of the material has been determined from UV spectra and it is found to be 4.96 eV for the parent compound. The lone pair of electron state is identified from the EPR spectra. The SEM micrographs have shown the presence of fine crystallites with irregular morphology. The average particle size of the powders is ranging between 25-35 μm. From the above studies, it has been concluded that pure crystals of LaNiO₃ and Praseodymium substituted compounds can be conveniently synthesized by molten salt technique.