Synthesis, structural, magnetic and electrical properties of nominal La0.67Ba0.33-xNaxMnO3 (0 ≤ x ≤ 0.33) manganites

Complete nominal solid solutions La0.67Ba0.33-xNaxMnO3 (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 LaαBaβNaλMnO3-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 Na0.55Mn2O4·1.5H2O. 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.