Perovskite type lanthanum manganite: Morpho-structural analysis and electrical investigations

• Published in: Journal of rare earths Vol. 36; no. 5; pp. 499 - 504
• Main Authors: Sfirloaga, Paula, Poienar, Maria, Malaescu, Iosif, Lungu, Antoanetta, Vlazan, Paulina
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.05.2018
• Subjects: Electrical investigations; Physico-chemical properties; Rare earths; Sol–gel method; Rare earths; Sol–gel method; Physico-chemical properties; Electrical investigations
• ISSN: 1002-0721; 2509-4963
• DOI: 10.1016/j.jre.2017.10.009

Perovskite-type oxides of LaMnO3 were synthesized by means of the sol–gel method, in the presence of citric acid as gelling agent. The precursors used were Mn(NO3)2·H2O, La2O3, and NaOH, mixed in the stoichiometric ratio to obtain perovskite materials. The obtained gel was heat-treated at 400, 600 and 800 °C respectively, for 6 h. X-ray diffraction and FT-IR spectroscopy were used to analyze the phase transformation as a function of temperature, and the Rietveld refinement was used in order to characterize the materials obtained structurally. The average crystallite size of the products was calculated from XRD data and the average particle size was measured from the TEM micrographs. At 600 °C, the synthesized compound is well-crystallized, showcases a perovskite structure (Pm-3m space group), and exhibits uniform and homogeneous hexagonally-shaped particles, with sizes in the 20–50 nm range. Complex impedance measurements in the 20–2 × 106 Hz frequency range were carried out at different temperatures (26–115 °C), and the electrical conduction mechanism is discussed. Rietveld refinement for LaMnO3 heat-treated at 600 °C and TEM images for LaMnO3 heat-treated at different temperatures: 400 °C (a), 600 °C (b), 800 °C (c). [Display omitted]