Phase relations, crystal structure, and phase transformation of In1−xNb1−xTi2xO4 (0 ≤ x < 0.45) in In2O3–Nb2O5–TiO2 system

• Phase relations of In2O3–Nb2O5–TiO2 ternary system were constructed.
• Crystal structures of a novel solid solution In1−xNb1−xTi2xO4 were determined.
• Crystal structure of InNbTiO6 was amended to be a wolframite-type structure.
• Composition-driven phase transformation of In1−xNb1−xTi2xO4 was investigated.

Phase relations, crystal structures, and phase transformation of In1−xNb1−xTi2xO4 (0 ≤ x < 0.45) in In2O3–Nb2O5–TiO2 ternary system were investigated for the first time. A number of samples with different compositions were prepared by a solid-state reaction method, and phase assembles were analyzed by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron probe micro-analysis (EPMA). Five three-phase regions, ten two-phase regions, and six single-phase solid solutions were determined in this system. The solid solution of In1−xNb1−xTi2xO4 (0 ≤ x < 0.45) is composed of both ordered monoclinic wolframite-type structure (0 ≤ x < 0.35) and disordered orthorhombic α-PbO2 type structure (0.35 < x < 0.45). Driving force for composition-driven phase transformation in In1−xNb1−xTi2xO4 (0 ≤ x < 0.45) stems from the ordering of cations. The ever reported compound InNbTiO6 with an orthorhombic α-PbO2 type structure was amended to be a monoclinic wolframite-type structure. Present investigations will be useful for the whole ceramic community working with In2O3–Nb2O5–TiO2 ternary system as well as for the development of functional materials.

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