Sol gel synthesis of multiphase lanthanum oxicarbonate and langasite thin films

Precursors of lanthanum oxide and of (3La2O3, 5Ga2O3, SiO2) system were first elaborated then thermally decomposed into polycrystalline lanthanum oxide and langasite La3Ga5SiO14. The as prepared lanthanum oxide powder was then hydrated and carbonated to give hydroxicarbonates: thermal decomposition of these complex system La2O3-X(OH)y(CO3)z was studied by Fourier Transform infrared spectroscopy. Spin coating process applied to these precursors was optimized to elaborate thin films of lanthanum oxicarbonate La2O2CO3, lanthanum oxide La2O3 and langasite, on silicium substrates (Si-(001)). Thin films are partly textured. Making use of same spin coating process, multiphase thin films of langasite covered with La2O3 particles were obtained.Precursors of lanthanum oxide and of (3La2O3, 5Ga2O3, SiO2) system were first elaborated then thermally decomposed into polycrystalline lanthanum oxide and langasite La3Ga5SiO14. The as prepared lanthanum oxide powder was then hydrated and carbonated to give hydroxicarbonates: thermal decomposition of these complex system La2O3-X(OH)y(CO3)z was studied by Fourier Transform infrared spectroscopy. Spin coating process applied to these precursors was optimized to elaborate thin films of lanthanum oxicarbonate La2O2CO3, lanthanum oxide La2O3 and langasite, on silicium substrates (Si-(001)). Thin films are partly textured. Making use of same spin coating process, multiphase thin films of langasite covered with La2O3 particles were obtained

Electrical conductivity of BaCeO3 synthesized by new sol-gel method

Polycrystalline BaCeO3 was prepared using new sol-gel processing at low temperature. The sample was characterized by X- ray diffraction and transmission electronic microscopy. The refined lattice parameters were found to be equal to: a = 8.782 Å, b = 6.240 Å, c = 6.217 Å. Electrical conduction was studied in the temperature range 150 to 950°C. The apparent conductivity of compacted samples was found to increase with temperature in a non linear way, from σ =2.49 10-7 S.m-1 at T =150°C to σ = 1.55 10-3S.m-1 at T =950°C. The activation energy is not constant and was found to increase from about 0.21 eV (in the temperature range: 150°C - 450°C) to 0.94 eV (in the temperature range 450°C - 950°C)Polycrystalline BaCeO3 was prepared using new sol-gel processing at low temperature. The sample was characterized by X- ray diffraction and transmission electronic microscopy. The refined lattice parameters were found to be equal to: a = 8.782 Å, b = 6.240 Å, c = 6.217 Å. Electrical conduction was studied in the temperature range 150 to 950°C. The apparent conductivity of compacted samples was found to increase with temperature in a non linear way, from σ =2.49 10-7 S.m-1 at T =150°C to σ = 1.55 10-3S.m-1 at T =950°C. The activation energy is not constant and was found to increase from about 0.21 eV (in the temperature range: 150°C - 450°C) to 0.94 eV (in the temperature range 450°C - 950°C)

Magnetic and Nanostructural Properties of Cobalt–Zinc Ferrite for Environmental Sensors

In this study, we compare nanoparticles (NPs) of Co0.5Zn0.5Fe2O4 spinel ferrite produced by a novel simple synthetic technique with those made by standard co-precipitation, sol-gel, and hydrothermal methods. The novel process is based on the addition of a very small amount of ethanol (only 2 vol% in water with a low ethanol:metals molar ratio of 0.5:1, not a co-solvent) during co-precipitation to synthesize a nanopowder, which formed single-phase magnetic spinel ferrite when heated at 700 !C. This technique produced cobalt–zinc ferrite NPs smaller than those formed by the other methods, with an average crystallite size of 17 nm calculated from X-Ray Diffraction and NPs sizes around 30 nm observed by scanning electron microscopy. A surface area of 32 m2/g, and a total pore volume of about 0.56 cm3/g, were determined by the BET isotherm. The best catalytic capabilities for converting ethanol vapor to CO, CO2, and H2O, as well as magnetic properties, were obtained for Co0.5Zn0.5Fe2O4 synthesized by the ethanol-assisted co-precipitation. The ethanol conversion rate rapidly increased above 175 !C, and the total conversion of ethanol was achieved at a relatively low temperature of 230 !C. This sample also had the largest magnetization of 58.2 A m2 kg"1 at 3 T, and a very small, near superparamagnetic, coercivity

The influence of synthesis way and dopant on the crystallites size of ceria

The present paper deals with the preparation of pure ceria by different methods : a conventional precipitation and a new sol-gel process. The size of crystallites was also carried out, aiming at studying the role of synthesis way on properties of pure ceria.
In order to investigate the influence of doping, samples with different molar contents of Mn$^{2+}$ were synthesized by co-precipitation. The doping level in all samples is expressed in molar percentage. A linear correlation between the lattice parameters and the Mn content confirm the incorporation of Mn in the ceria lattice. The evolution of crystallites size versus the lattice parameter was investigated