Papers by Keyword: Perovskite

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Authors: Hiromi Nakano, Nobuo Ishizawa, Hirohisa Sato, Naoki Kamegashira
Abstract: The BaLn2Mn2O7 (Ln = rare earth) has a Sr3Ti2O7-type structure with double block oxygen octahedra belonging to the Ruddlesden-Popper-Type homologous series AO(ABO3)2. In-situ measurement of the phase transition for BaLn2Mn2O7 was performed using single-crystal X-ray diffraction and a high-temperature transmission electron microscope (TEM). Two types of transitions were observed in BaPr2Mn2O7: the transition from primitive tetragonal (P42/mnm) to body-centered tetragonal (I4/mmm) at around 400 K and the first-order phase transition at around 1040 K. Multiple phase transitions were also observed in BaEu2Mn2O7, with one from P42/mnm to I4/mmm at around 400 K and another, above 550 K, as a first-order phase transition. The high-temperature phase had a 1.5% lattice mismatch along the c-axis compared with the low-temperature phase. We succeeded in recording for the first time in-situ structural change in BaGd2Mn2O7 as a movie by high-temperature TEM. The high-temperature phase nucleated parallel to the (00l) plane as a layer above 550 K and grew until covering the entire inspected region at around 1023 K. The first-order phase transition was caused by the structural and/or electrical distortion of the layered perovskite structure composed of Jahn-Teller ion Mn3+.
Authors: Wei Liang Zhao
Abstract: A novel two-step sequential deposition method is proposed for the preparation of CH3NH3PbI3 for perovskite solar cell. In order to increase the crystallinity of the PbI2 film, rapidly drop the anhydrous chlorobenzene to the center of the substrate at 6 seconds of spin coating. Ultimately, the quality of the CH3NH3PbI3 film is improved. Through the transmission spectrum of CH3NH3PbI3 thin films, it is clear to see the use of the additive reduces the transmittance of the film. The PL spectroscopy of CH3NH3PbI3 thin films dropping with different additives shows that CH3NH3PbI3 thin films all have an emission peak at 768nm. The J-V test curve of the perovskite solar cell shows that the use of the additive improves the power conversion efficiency.
Authors: Shu Ai Li, Bill Bergman, Zhe Zhao
Abstract: Lanthanum aluminate powders were prepared via a polymer complexing method by using PEG as complexing agent. The LaAlO3 powder was characterized by XRD and SEM. The influence of processing parameters such as molar ratio of PEG monomers to metal cations (PEG:Men+) and aging process on the phase purity and powder morphology were investigated. The calcined powder with the PEG:Men+ ratio larger than 2:1 may contain the secondary phase, namely La2O3. The formation of phase pure LaAlO3 powder occurs when the PEG:Men+ ratio is 1:1 or enough gelation time is involved. Although the phase pure powder is obtained by this PEG method, all the single phase LaAlO3 powders are found to have seriously aggregated particles. The weakly agglomerated powder morphology is only found in the powders which contain La2O3.
Authors: Anjali A. Athawale, Malini Bapat
Abstract: Barium zirconate, a perovskite oxide has been synthesized by a new procedure using solid state metathesis reaction precursors subjected to sonication. We report the lowest temperature of synthesis with particle size ranging from 20 to 30 nm. The initial stage involves formation of composite hydroxide nanoparticles by the solid state reaction of precursor salts with KOH at ambient temperature followed by sonication. BaZrO3 formation as a consequence of ultrasonicator output power variation and ultrasonic time variation has been studied. Results indicate that the process is convenient, low energy, environmentally benign and having narrow particle size distribution of BaZrO3.
Authors: Prawistin Noorlaily, Maria Ulfa, Satria Zulkarnaen Bisri, Ferry Iskandar
Abstract: Hybrid perovskite is one of the emerging materials which is currently being widely investigated for solar cells. Here we report the synthesis and characterization of perovskite compound which can be used as a light harvester in photovoltaic cells, which is CH3NH3PbI(3-x)Clx. The perovskite materials were synthesized using solution-based methods. Several parameters are investigated in the synthesis of CH3NH3PbI(3-x)Clx perovskite, which are the influence of precursor composition, synthesis temperature , precursor concentration, and the annealing temperature. These parameters are optimized against the absorbance and bandgap of the synthesized CH3NH3PbI(3-x)Clx thin film. The optimized perovskite thin film is obtained with excellent absorption capabilities for solar cell applications.
Authors: Yasuhiro Harada, Yoshitaka Ishikawa, Jun Kuwano, Yasukazu Saito
Authors: Hiroshige Matsumoto
Abstract: Hydrogen separation is one of the key techniques for the forthcoming hydrogen economy. This paper describes a possible electrochemical method and materials for hydrogen separation: mixed proton-electron-conducting membrane that can permeate hydrogen selectively from hydrogen-containing gases, such as reformed gases of hydrocarbons. Proton-conducting perovskite-type solid electrolytes are first introduced as the base material of the mixed conductor. Some transition metal-doped perovskites are shown to have a mixed conductivity of protonic and electronic charge carriers, revealed by electrochemical and X-ray-spectroscopic measurements.
Authors: Chakrit Soongprasit, Duangdao Aht-Ong, Duangduen Atong
Abstract: Perovskite-type oxide with transition metal as active site presented a promising potential catalyst for tar elimination in gasification process. LaNi1-xCoxO3 (x= 0, 0.3, 0.5, 0.7, and 1) were prepared by sol-gel method. The XRD profiles of the calcined catalysts revealed the mixed metal oxide forms including LaNiO3 and LaCoO3 rhombohedral structures. Good dispersion of La, Ni, and Co with homogenous structure was observed in synthesized catalyst. The particle size and surface area were in the range of 12.64-21.86 μm and 3.89-11.69 m2 /g, respectively. Activity of prepared catalysts on tar elimination was carried out using steam reforming of toluene as tar model compound at 500, 600, 700, and 800°C. Product distributions obtained from reforming reaction with LaNi1-xCoxO3 were between 40.24-88.84% of gas, 10.99-59.59% of liquid, and 0.15-0.17% of solid. Conversion to CO and H2 were found to increase with the reaction temperature. The maximum carbon and hydrogen conversion to syngas, CO and H2, of approximately 78.42% and 83.49% with acceptable heating value were occurred at 800oC using LaNiO3 as catalyst. Crystal structure of used catalysts clearly showed destruction of perovskite structure and transformation to metallic Ni and Co at effective temperature.
Authors: J.W. Chen, Bor Kai Wang, Jimmy C. Hsu, G.N. Rao
Abstract: We report the results of the broadband dielectric constant and loss tangent of the new complex perovskites Ba3MnTa2O9 with the test frequency f in different ranges from 1 kHz to 15 GHz. For the test frequency f below 1 MHz, the dielectric constant and loss tangent of the specimens were measured using a LCR meter with four-terminal configuration. The measurements at frequencies between 50 MHz and 1 GHz were performed by the lumped impedance method, which uses an impedance analyzer to measure the complex impedance of the specimen. At frequencies above 1 GHz, two samples with diameter 9 mm and different thicknesses (2.73 mm and 5.42 mm) were measured by a home-made Hakki-Coleman resonator. The TE011 resonant peaks were found and identified with an Agilent PNA net-work analyzer. The dielectric constants were found to remain almost constant with the test frequency at room temperature. The calculated values of the real part dielectric constants are 17.74 and 17.53 at 9.86 GHz and 15.43 GHz, respectively. The unloaded Q factors deduced from curve fitting of the peaks are both around 200.
Authors: A.Y. Kryukov, A.V. Vishniakov, Cesare Oliva, Lucio Forni
Abstract: High surface area nano-sized catalysts with the general formula La0.9M0.1CoO3 (M=Ce, Pr, Tb) were synthesised by a novel flame-spray-pyrolysis method. All the prepared samples possessed the LaCoO3 perovskite-like structure and consisted of 30-60 nm particles, but existing as large (80-200 nm) agglomerates. Their surface area ranged from 45 to 60 m2/g. All the catalysts showed a very high activity for methane flameless combustion, attaining 100% conversion at temperatures Tf, between 495 and 515 0C, depending on the nature of the M doping ion. The results of life-tests did not show any decreasing of catalytic activity after 50 h under the reaction conditions at Tf. The thermal stability under high temperature application was investigated by overheating the catalysts twice at 800 0C for 1 hr in a flowing reacting gas mixture, fast deactivation cycles, and then measuring methane conversion at Tf. All the catalysts showed a significant decrease of activity, depending on the chemical composition. Taking account of the results of SEM analysis, this was attributed to sintering, connected with the Gibbs instability of nano-sized materials.
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