Synthesis, structural, magnetic and electrical properties of nominal La_0.67Ba_0.33-xNa_xMnO₃ (0 ≤ x ≤ 0.33) manganites

¹ Laboratoire de Physico-chimie des Matériaux, Département de Physique, Faculté des Sciences de Monastir, 5019, Université de Monastir, Tunisie
² Laboratoire des Matériaux et du Génie Physique (CNRS UMR 5628), Minatec Bâtiment INPG, parvis Louis Néel, BP 257, 38016 Grenoble Cedex 1, France
³ Laboratoire de Physique des matériaux et nanomatériaux appliqués à l’environnement, Faculté des Sciences de Gabes, Département de Physique, 6079, Université de Gabes, Tunisie

^a e-mail: hcini_sobhi@yahoo.fr

Abstract

Complete nominal solid solutions La_0.67Ba_0.33-xNa_xMnO₃ (0 ≤ x ≤ 0.33) have been elaborated by ceramic route at 1200°C. ICPAES chemical analysis and XRD Rietveld structure refinement revealed that the nominal Na content is not achieved by our ceramic method. The chemical formula should be rather written as La_αBa_βNa_λMnO_3-δ with a significantly lower Na content (λ), than the nominal one (x), and with a slight deficit (δ) in oxygen content, leading to the appearance of two minor secondary phases identified as Mn₃O₄ and Na_0.55Mn₂O₄·1.5H₂O. Magnetization and electrical resistance vs. temperature show paramagnetic/semiconductor – ferromagnetic/metallic transitions with only a slight decrease in magnetic and electrical transition temperatures when Na content increases. Such amount of this decrease is not expected according to the nominal Na content giving a significant difference between nominal and experimental Mn⁴⁺/Mn³⁺ ratios.