Synthesis and crystal structure of novel nonstoichiometric suboxide solid solutions, Ti12−δGaxBi3−xO10

Conference Dates

March 10-14, 2019


Single crystals of new Ti12−δGaxBi3−xO10 compounds (x = 1.42–1.74, δ = 0.77–0.62) were prepared at 900 °C with a Bi flux. Crystal structure analysis by X-ray diffraction (XRD) revealed that the solid solutions are isostructural with Ti12−δSn3O10 (cubic, space group Fm-3m).1) The δ and x values were determined by refinement of the occupancies for the Ti2 and Ti4 sites, and Ga site, respectively (Table 1). The cell parameter a decreases from 13.5616(3) Å to 13.5402(5) Å with increasing Ga content, x, while the total valence electron number of Ti12−δGaxBi3−xO10 was maintained at 117.1 by decreasing Ti defects, δ. Stella octangula is formed by sharing of the edges of four supertetrahedra composed of O-centered Ti tetrahedra and trigonal bipyramids (oxide part) (Figure 1). Another superpolyhedron is formed by sharing of the pyramidal planes of Ga/Bi-centered Ti mono-caped square antiprisms (intermetallic part). These two parts are incorporated in the structure. A polycrystalline bulk of a solid solution with x = 2.01, δ = 0.67 (a = 13.53772(13) Å) was synthesized by reaction sintering at 950 °C from the mixture of Ti, TiO2, Bi2O3, and Ga2O3. The resistivities measured for the bulk were 2.2–2.4×10−5 Ωm in the temperature range from 10 K to 300 K.

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