Structural, Vibrational, and Magnetic Characterization of Orthoferrite LaFeO3 Ceramic Prepared by Reaction Flash Sintering

Abstract

LaFeO3 perovskite ceramics have been prepared via reaction flash technique using Fe2O3 and La2O3 as precursors. The obtained pellets have been investigated using several techniques. The formation of LaFeO3 has been clearly confirmed by X-ray diffraction. The scanning electron microscopy micrographs have shown the microporous character of the obtained pellets due to the low temperature and dwell time used in the synthesis process (10 min at 1173 K). The orthorhombic-rhombohedral phase transition has been observed at approximately 1273 K in differential thermal analysis measurements, which also allows us to determine the Néel temperature at 742 K. The fitted Mössbauer spectra exposed the presence of a single sextet ascribed to the Fe+3 ions in the tetrahedral site. Finally, magnetic measurements at room temperature indicate the antiferromagnetic character of the sample.

LaFe1–xCoxO3 Perovskite Nanoparticles Supported on Ni(OH)2 as Electrocatalyst for the Oxygen Evolution Reaction

“…The oxygen octahedral bending vibration of B 2g , B 1g , and B 3g symmetry are attributed to the pair of peaks around 391, 421, and 475 cm –1 , respectively. , The asymmetric stretching vibrations with A g symmetry are considered the cause of the broad peak around 515 cm –1 , which is the Jahn-Teller distortion. , The in phase symmetric oxygen stretching vibrations of B 1g symmetry are the intense peaks in the range of 600–700 cm –1 , while the low intense phonon mode over 800 cm –1 may be due to the multiphonon processes. Lastly, the broad features above 1000 cm –1 are the second order scattering …”

“…Lastly, the broad features above 1000 cm −1 are the second order scattering. 35 For the cobalt doped sample LFCO-0.2, all peaks were blueshifted toward higher Raman shift by 6−10 cm −1 and it is attributed to the lattice strain, crystallite size effects, and structural distortions arising due to Co inclusion as the Co−O short-range ordering affects the long-range ordering of Co−O with the influence in the oxygen octahedral tilt, 31 while the Raman spectra of Ni(OH) 2 as shown in Figure S1b display the presence of a pair of peaks at the far end wavenumber region above 3500 cm −1 , particularly at 3575 and 3638 cm −1 , corresponding to the symmetric O−H stretching vibration of lattice OH functionalities and the O−H vibration of the intercalated H 2 O layer in the interlamellar space of the Ni(OH) 2 structure, respectively. This observation confirms that the prepared Ni(OH) 2 sample is crystallized into the αpolymorph of Ni(OH) 2 with trigonal symmetry and in prefect agreement with the PXRD results, 36 whereas the sharp intense peak observed at 476 cm −1 along with a broad tail around 452 cm −1 is assigned to the stretching lattice modes of Ni−OH.…”

“…32,35 The asymmetric stretching vibrations with A g symmetry are considered the cause of the broad peak around 515 cm −1 , which is the Jahn-Teller distortion. 33,35 The in phase symmetric oxygen stretching vibrations of B 1g symmetry are the intense peaks in the range of 600−700 cm −1 , while the low intense phonon mode over 800 cm −1 may be due to the multiphonon processes. Lastly, the broad features above 1000 cm −1 are the second order scattering.…”

Touch‐free reactive flash sintering of dense strontium hexaferrite permanent magnet

“…Separately, we have shown that chemical reaction and sintering in multicomponent ceramics can occur in a single step by flashing mixtures of powders of constituent oxides: so‐called reactive flash sintering (RFS) 13 . Since then, this technique has been applied to process ferrites, 14,15 ferroelectrics, 16,17 high‐entropy oxides, 18–21 and Li‐ion ceramic electrolytes 22,23 …”

“…Separately, we have shown that chemical reaction and sintering in multicomponent ceramics can occur in a single step by flashing mixtures of powders of constituent oxides: so-called reactive flash sintering (RFS). 13 Since then, this technique has been applied to process ferrites, 14,15 ferroelectrics, 16,17 high-entropy oxides, [18][19][20][21] and Li-ion ceramic electrolytes. 22,23 Here, we explore the application of the touch-free FS technique to RFS (TF-RFS), that is, preparation of multicomponent oxides by flash without the use of electrodes.…”