A newly developed YbFeO3-YbCrO3-YbMnO3 pseudo-ternary phase diagram: Crystal structure, optical properties, and dielectric properties of seven selected orthorhombic ternary solid solution compounds

We construct a YbFeO3-YbCrO3-YbMnO3 pseudo-ternary phase diagram that illustrates the different equilibrium phases regions where orthorhombic, hexagonal, and orthorhombic, and hexagonal phases at room temperature coexist. Thirty-three Yb:Fe:Cr:Mn molar ratio compositions were designed using solid-state reactions. They were characterized by X-ray diffraction. Poor miscibility of the hexagonal single phase in a small region of the YbMnO3-YbFeO3 pseudo-binary phase was found. The maximum miscibility of Mn into the orthorhombic phase is found in the YbFe0.50Cr0.25Mn0.25O3, YbFe0.375Cr0.375Mn0.25O3, and YbFe0.25Cr0.50Mn0.25O3 intermediate ternary ceramic compound. Beyond this concentration of Mn, the YbFeO3 - YbCrO3 - YbMnO3 pseudo-ternary system breaks down into mixing hexagonal and orthorhombic phases. Once the different phases were established; the crystalline structure, microstructure as well as optical and dielectric properties were investigated in seven selected compositions in the orthorhombic zone, where the total Fe – Cr and the partial Mn miscibility tunes the cell volume. SEM images reveal grains coalescence, indicating incipient fusion in the YbFeO3 sample. As Cr and Mn increase, the sign of incipient fusion and grain size decreases. The dielectric properties were evaluated as a function of temperature, and through these quantities it is found that the electrical conductivity increases for the intermediate ceramic compound. This fact agrees with the optic band gap, Eg, which decreases for these intermediate compounds. According to the dielectric study, we found that the decrease in the Eg is mainly associated with charge carriers polarons (∼0.20–0.25 eV) at low-temperature and oxygen vacancies (0.55–0.61 eV) at high temperatures. © 2024 Acta Materialia Inc.