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The synthesis, thermal behavior and electrical properties of a series of undoped and 1% Ga- or Y-doped lanthanum manganite compounds, obtained via the sol–gel technique, are reported. Scanning electron microscopy (SEM/EDX), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) analyses were performed on all synthesized samples. The XRD results confirmed a good crystallinity for all studied samples, and a change in the crystal structure of Ga- or Y-doped lanthanum manganite (Pm-3m space group) was observed compared to the pristine sample (R-3c space group). Thermal analysis highlighted a different behavior of the doped samples compared to the undoped sample, observed by the different mass losses in the analyzed temperature range. For these materials, it is shown for the first time that the static electrical conductivity, σDC, of Ga- or Y-doped LaMnO3 compounds increases compared to the σDC of the pristine sample, and the thermal activation energy of the process of electrical conduction, EA,cond, increases linearly with the temperature for all three studied samples. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a study regarding the cobalt ferrite obtaining in the Co x Fe3−x O4 system, where x =0.5; 1.0; 1.5 by two different synthesis methods. The Co(II) and Fe(III) complexes method leads to the thermal decomposition at 300°C for this precursor with the pure cobalt ferrite (CoFe2O4) formation for x =1 or mixed with γ-Fe2O3 for x =0.5 and Co3O4 for x =1.5. By co-precipitation followed by ultrasonic milling synthesis method the pure cobalt ferrite is obtained at 90°C for x =1 or mixed with Fe3O4 for x =0.5 and Co3O4 for x =1.5. When the initial samples are heated at 400°C, the identified oxide phase is identical for the same value of x. The obtained powders were investigated by X-ray diffraction (XRD), FTIR spectrometry and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDX). The final product has nanometric size and has a strong tendency to agglomerated, thus influencing the saturation magnetization value. The shape of the magnetization curves is influenced by the presence of the secondary phases for x ≠1. [Copyright &y& Elsevier]

Nitrogen containing lanthanum manganite perovskite material has been successfully synthesized through sol-gel method using urea (CH 4 N 2 O) as a nitrogen source. The obtained powders were followed thermal treatment at low temperature. In order to achieve a comparative study on the obtained materials, three concentrations of urea were used (0.05; 0.1 and 0.15%). The characteristic of the materials were examined by differential thermal analysis (TG/DTA/HF), X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), scanning/transmission electron microscope (SEM/TEM), energy-dispersive X-ray spectroscopy (EDX) and electrochemical measurements were made. The XRD patterns show that all analyzed sample are well crystallized and present a perovskite single phase with the cubic structure, space group: Pm-3m, with the average size of crystallites around 30 nm. All the N-doped LaMnO 3 perovskites exhibit remarkable electrocatalytic effect on the redox reaction of potassium ferricyanide improving redox peak current. Image 1 • Nitrogen doped LaMNO 3 materials was carried out for the first time. • Electrochemical behaviour of N–LaMnO 3 on graphite electrode was investigated. • By sol-gel technique was obtained nanometric particles with different morphologies. [ABSTRACT FROM AUTHOR]