Electrical assessment of brownmillerite-type calcium ferrite materials obtained by proteic sol-gel route and by solid-state reaction using mollusk shells

• Published in: Journal of solid state chemistry 2021-07, Vol.299, p.122172, Article 122172
• Main Authors: Lima, Chrystian G.M., Araújo, Allan J.M., Silva, Rinaldo M., Raimundo, Rafael A., Grilo, João P.F., Constantinescu, Gabriel, Kovalevsky, Andrei V., Macedo, Daniel A.
• Format: Article
• Language: English
• Subjects: Ca2Fe2O5; Electrical properties; Mollusk shells; Proteic sol-gel synthesis; Solid-state reaction
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2021.122172

In this work, brownmillerite-type calcium ferrite (Ca2Fe2O5) ceramics were prepared by two distinct routes, namely by a proteic sol-gel synthesis using commercial flavorless gelatin, and by a solid-state reaction method using mollusk shells. XRD analyses revealed single phase brownmillerite-type calcium ferrites in both cases. SEM-EDS analysis of sintered Ca2Fe2O5 ceramics revealed larger grain sizes for the samples prepared via the solid-state reaction. All samples possessed a p-type conduction mechanism, with the largest power factor of ~2 ​μW ​m-1 K−2 at 450 ​°C observed for the samples obtained via the solid state reaction. The charge transport mechanism was found to depend on the preparation route. The obtained results demonstrated that the proposed synthesis routes can be successfully employed for the preparation of single-phase brownmillerite-type materials. Microstructure and electrical properties of calcium ferrite obtained by two environmentally friendly synthesis methods. [Display omitted] •Calcium ferrite synthesized by a proteic sol-gel route.•Solid-state reaction route using mollusk shells, as a source of calcium carbonate.•Low-cost and environmentally friendly methods for synthesizing Ca2Fe2O5.•Structural, microstructural and electrical properties of calcium ferrite.