Gd2O3–SrO–Fe2O3 system: The phase diagram and oxygen content in oxides. (December 2021)

• Record Type: Journal Article
• Authors: Khvostova, L.V.; Volkova, N.E.; Gavrilova, L.Ya.; Maignan, A.; Cherepanov, V.A.
• Is Part Of: Materials today communications. Volume 29(2021)
• Publication Date: 2021-12
• Subjects: Oxide materials -- Crystal structure -- Phase diagrams -- Thermal analysis X-ray diffraction; Materials science -- Periodicals; 620.11
• DOI: 10.1016/j.mtcomm.2021.102885
• Languages: English
• ISSNs: 2352-4928

Abstract

Abstract: The phase diagram for the ½ Gd2 O3 –SrO–½ Fe2 O3 system was constructed at 1100 °C in air. Six types of phases: Sr1- х Gd х FeO3-δ (cubic, SG Pm 3 ̅ m, with 0 . 05≤ х ≤0.30 and orthorhombic, SG Pbnm, with 0 . 80≤ х ≤1.00), Sr2- y Gd y FeO4-δ where y =0.75 and 0.80 with the K2 NiF4 -type structure, Sr3- u Gd u Fe2 O7-δ (two tetragonal oxides u =0 and 0.3 with SG I4/mmm and u =1.9 with SG P4 2 /mnm ), and Sr3.2 Gd0.8 Fe3 O10-δ with the tetragonal structure (SG I4/mmm ) were obtained. The structural parameters of single-phase samples were refined by the Rietveld analysis. A revised phase diagram for the GdFeO3 -SrFeO3- δ system in the "T – composition" coordinates is proposed. Oxygen content in single-phase oxides is determined by TGA and iodometric titration. Oxygen content in the perovskite-type oxides gradually increases with Gd concentration. RP-type oxides with n =1 Sr2- y Gd y FeO4-δ and with n =2Sr1.1 Gd1. 9 Fe2 O7- δ exhibit negligible oxygen losses with temperature while those with n=2 Sr3- u Gd u Fe2 O7-δ (0≤ u ≤0.3) and n =3 Sr3.2 Gd0.8 Fe3 O10-δ demonstrate significant changes in oxygen content associated to higher Fe oxidation states. Highlights: The phase diagram for the ½Gd2 O3 –SrO–½Fe2 O3 system was constructed at 1100 °C in air. A revised phase diagram for the GdFeO3 -SrFeO3- δ system was proposed. The structural parameters of oxides were refined by the Rietveld method. Oxygen content in single-phase oxides was determined by TG and iodometric titration.