Synthesis and characterization of nano-LaFeO3 powders by a soft-chemistry method and corresponding ceramics (original) (raw)
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Nanocrystalline LaFeO 3 powders synthesized by the citrate–gel method
Materials Letters, 2006
A novel sol–gel process was developed for preparing nano-sized, perovskite-type LaFeO3 powder by the thermal decomposition of the gel-complex of LaFe–(C6H8O7·H2O). The structural evolution has been systematically investigated by X-ray diffraction (XRD), differential thermal analysis (DTA) and thermogravimetric analysis (TGA). Perovskite powder of ∼ 25 nm size could be obtained at a temperature of ∼ 600 °C without formation of any secondary phases of La2O3 and Fe2O3 single oxides and no requirements of high temperature/vacuum/pH control etc. Analysis of the X-ray powder diffraction data showed a decrease in the value of lattice strains with increasing decomposition temperature, whereas the particle size increases with increasing decomposition temperature.
SciMedicine Journal, 2019
Perovskite LaFeO3 is one of the most useful materials for the application in a catalyst, gas sensors, and fuel cells, etc. LaFeO3 nanoparticles were synthesized by the citrate sol-gel method. According to the TG-DTA analysis on LaFeO3 xerogel powder, the proper crystallization temperature was found to be at 450 °C. The TEM images also show clear crystal formation was started at 450 °C. The LaFeO3 nanocrystalline particles were obtained by sintering the calcined powders at different temperatures (800 °C, 900 °C, and 1000 °C) for 4 hours. The resulting particles were characterized by XRD, EDXRF, FT IR, and SEM analysis. At 900 °C, the XRD pattern of LaFeO3 shows an orthorhombic crystal structure. The average crystallite sizes vary between 30-60 nm and the increase in crystallite size with increasing sintering temperatures and it may be due to the increase in grain growth. FT IR analysis shows strong La-O and Fe-O vibrations. Based on the XRD and FT IR data, the optimum sintering tempe...
Solid State Ionics 249–250 (2013) 1–5, 2013
The optical and magnetic properties of nano-LaFeO3 powders prepared by a starch assisted soft-chemistry synthesis and corresponding ceramics have been investigated. Magnetic measurements on LaFeO3 powders with crystallite sizes of 37–166 nm show pronounced magnetization hysteresis loops. Measurements at 300 K reveal that the coercivity (Hc) of 19–32 kOe depends on the crystallite size, whereas the low remanence values (Mr) of roughly 0.2 emu/g and the maximal magnetization (Mmax) at 90 kOe of 1.05–0.85 emu/g are only slightly changing. Investigations at 10 K reveal a loop shift (exchange bias) up to 12 kOe in the negative direction depending on the crystallite size. Ceramic bodies, sintered at ≥ 1300 °C possess a considerably reduced hysteresis loop. Hc is decreased up to 3.0 kOe, whereas Mr and Mmax are slightly increasing. None of the samples reaches saturation at 90 kOe indicating an anti-ferromagnetic ordering of the spins. The optical band gaps of the LaFeO3 samples were determined by means of diffuse reflectance spectra. For all LaFeO3 powders similar band gaps of 2.65 eV were observed. However, ceramics with grain-size significantly larger than 250 nm show smaller band gap values up to 2.12 eV.
Journal of Solid State Chemistry 287 (2020) 121380, 2020
Nanocrystalline Li0.5Fe2.5O4 was prepared by a starch-based soft-chemistry synthesis. Calcining of the (LiFe)-gel between 350 and 1000 °C results in Li0.5Fe 2. O4 powders with crystallite sizes from 13 to 141 nm and specific surface areas between 35 and 7.1 m^2 g-1. XRD investigations reveal the formation of ordered Li0.5Fe2.5O4. Sintering between 1050 and 1250 °C leads to ceramics with relative densities of 67 95 % consisting of grains between 0.3 and 54 µm. As the sintering temperature increases a rising weight loss of the ceramic samples was observed due to the loss of Li2O. Temperature-dependent magnetic measurements indicate a superparamagnetic behaviour for the nano-sized samples. Field-dependent measurements at 3 K of ceramics sintered between 1050 and 1200 °C show increasing saturation magnetization values (M s) of 70.0 to 73.0 emu g-1 most likely due to the formation of lithium vacancies and a decrease of the inversion parameter. The magnetization drops down to 67.7 emu g-1 after sintering at 1250 °C caused by the formation of hematite. Diffuse reflectance spectra reveal an indirect allowed band gap decreasing from 1.93 to 1.60 eV depending on thermal treatment. DSC measurements of the order - disorder phase transition on nano-sized powders and bulk ceramics exhibit transition temperatures between 734 and 755 °C and enthalpy changes (trs H) ranging from 5.0 to 13.5 J g-1. The linear thermal expansion coefficient was found to be 11.4 10^- 6 K-1 .
Synthesis and Electrochemical Properties of LaFeO 3 Oxides Prepared Via Sol – Gel Method
2013
In this study, LaFeO3 oxides were prepared by citric acid sol–gel method. The samples were subjected to various calcination temperatures in order to investigate the physicochemical properties of the oxide affected by the parameter. Samples were characterized by XRD, TG/DTA, IR, laser granulometry and cyclic voltammetry. By imposing various calcination temperatures, phase evolutions were observed. However, the calcination temperature affects significantly the particle size and catalytic activity of the oxide at higher temperature. Oxygen evolution shows that the current density at 1,050 ◦C is five times greater than at 950 ◦C. From these results, the best calcination temperature can be chosen to arrive at the effective catalyst necessary for the desired catalytic reaction.
SYNTHESIS AND CHARACTERIZATION OF NANOCRYSTALLINE LaFeO 3 BY COMBUSTION ROUTE
2009
Orthorhombic structure perovskite LaFeO3 nanocrystalline with size ~27 nm were prepared by glycine combustion method. The prepared LaFeO3 nanocrystals were characterized by TG-DTA thermal analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic fluorescence microscopy (AFM) and Brunauer Emmett Teller (BET) nitrogen absorption. The LaFeO3 nanocrystals are more attractive in the field of catalytic application and process can be applied to prepared more other oxide nanocrystals such as LaCrO3, LaMnO3 etc.