In-situ formation of barium ferrite in iron-doped “tetragonal tungsten bronze”: Elaboration of room temperature multiferroic composites

Recent studies of ceramics of formula Ba₂LnFeNb₄O₁₅ (Ln=rare earth) with the “tetragonal tungsten bronze” (TTB) structure have correlated their room temperature multiferroics properties to the occurrence of barium ferrite parasitic phases. This work presents the elaboration of Ba₂LaFeNb₄O₁₅ and Ba₂EuFeNb₄O₁₅ composite samples with an excess of hematite in the TTB nominal composition. The influence of crystal-chemistry on the phase content and properties of Ba₂LnFeNb₄O₁₅ TTB composites is discussed. A particular focus on the mechanisms related to the in-situ formation of barium ferrite is given. We show that we can control the spurious ferrite phase in TTB multiferroic composites and thus modulate their magnetic response.