Synthesis Of La2 Research Articles

Facile synthesis of la2(co3)3-diatomite composites for the continuous removal of low-concentration phosphate

Facile synthesis of la2(co3)3-diatomite composites for the continuous removal of low-concentration phosphate

Synthesis of La2−xSrxCuO4 films via atomic layer-by-layer molecular beam epitaxy

Atomic layer-by-layer molecular beam epitaxy (ALL-MBE) is a sophisticated technique to synthesize high-temperature superconductor (HTS) materials. ALL-MBE produces single-crystal HTS films with atomically smooth surfaces and interfaces, as well as precise multilayer heterostructures engineered down to a single atomic layer level. This enables the fabrication of tunnel junctions, nanowires, nanorings, and other HTS devices of interest. Our group has focused on ALL-MBE synthesis and materials science of La2−xSrxCuO4 (LSCO), a representative HTS cuprate. In the past two decades, we have synthesized over three thousand LSCO thin films and characterized them by a range of analytical techniques. Here, we present in full detail a systematic process for the synthesis and engineering of atomically perfect LSCO films. The procedure includes the preparation of substrates, calibration of the elemental sources, the recipe for ALL growth of LSCO films without any secondary-phase precipitates, post-growth annealing of the films, and ex situ film characterization. This report should aid replication and dissemination of this technique of synthesizing single-crystal LSCO films for basic research as well as for HTS electronic applications.

Synthesis of La2(Zr0.7Ce0.3)2O7 nanopowder using a simple chemical precipitation method and heat treatment at high temperature

AbstractLa2(Zr0.7Ce0.3)2O7 ultrafine powder was prepared via a precipitation process using ZrOCl2.8H2O, Ce(NO3)3.6H2O, and La2O3 precursors. The thermal behavior, phase structure, particle size, and morphology of the nanostructured precipitate and the calcined powders were investigated. The thermal analysis results of the nanostructured precipitate showed that pyrolysis occurs at 600 °C. The X-ray diffraction analysis results of the calcined powders indicated that submicrometer crystalline phases of lanthanum zirconate pyrochlore and lanthanum cerate fluorite with approximately 50 % amorphous were formed at 1 100 °C. The powders calcined at 900 °C were composed of semi-crystallized nanoparticles including crystalline phases of lanthanum zirconate and cerate. The semi-crystallized nano-particles can potentially be used as raw material of new nanostructured thermal barrier coatings.

Synthesis of La2(Ni1-xCox)7 (x = 0.05, 0.1, 0.2) Hydrogen Storage Alloys by the Electro-Deoxidation Technique

La2(Ni1-xCox)7 (x = 0.05, 0.1, 0.2) alloys were synthesized directly from sintered mixture of La2O3 + NiO + CoO in the molten CaCl2 electrolyte by the electro-deoxidation method at 850°C and the electrochemical hydrogen storage characteristics of the synthesized alloys were observed. Sintering (at 1200°C for 3 h) converted the hygroscopic La2O3 (by the reaction with NiO) into the non-hygroscopic LaNiO3, La3Ni2O6.5 and La4Ni3O9 depending on the Co content of the oxide mixture. The X-ray diffraction peaks indicated that La2NiO4 was the main La-Ni-O phase formed as a result of partial reduction or dissociation reaction to initiate the LaNi5 phase formation. The target La2Ni7 phase formed much later than LaNi5 phase probably due to the sluggish reduction of LaOCl. It was observed that La2(Ni1-xCox)7 (x = 0.05, 0.1, 0.2) alloys had promising discharge capacities changed between 227 mA h g−1 (La2(Ni0.95Co0.05)7) and 332 mA h g−1 (La2(Ni0.8Co0.2)7) depending on the alloy Co content. This work clearly indicated that the electro-deoxidation was very effective method in the synthesis of the hydrogen storage materials.

Synthesis of La2(1–x)(MoO4)3:RE2x (RE = Eu, Tb) Phosphor Powders via a Sol-Gel Combustion Process and Their Photoluminescent Properties

Powder phosphors of La2(1–x)(MoO4)3:RE2x , RE = Eu3+ or Tb3+, were prepared by sol-gel combustion reactions with calcination temperatures of 600–900°C. Their reaction process, crystal structures, morphologies, and optical properties were characterized by differential scanning calorimetry, powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and photoluminescence spectroscopy, respectively. Our results reveal that all of these phosphors adopted the tetragonal crystal structure. The obtained La2(1–x) (MoO4)3:Eu2x phosphors exhibit a notable emission in the red light range which can be assigned to the 5D0 → 7F2 transition of Eu3+ upon excitation at 459 nm. When the phosphors were irradiated by 277 nm light, they showed predominant green emission (5D4 → 7F5) at 540 nm. The highest emission of the phosphors can be achieved by adjusting the doping concentration of Eu3+ at x =0.25 or Tb3+ at x =0.09.

Synthesis of La2(MoO4)3: electrocatalytic activity for the oxygen evolution in alkaline media

La-Mo oxides were synthesised by heating the powder, obtained from the reaction of lanthanum nitrate with molybdenum carbonyl in organic media, at 573 K for 2 h. The structure, morphology and chemical composition were determined by oxygen determination, atomic absorption spectrometry, X-ray diffraction and scanning electron microscopy. The results showed an amorphous structure. After heating the compound in vacuum, we obtained the X-ray diffraction pattern of La 2(MoO 4) 3. The electrochemical behaviour of the La–Mo oxides was determined in KOH 0.5 M. In the range 700–1000 mV vs Hg/HgO/KOH 0.5 M electrode, the results showed a very good performance for the oxygen evolution reaction.