New compounds In3Ti2AO10, In6Ti6BO22, and their solid solutions (A: Al, Cr, Mn, Fe, or Ga; B: Mg, Mn, Co, Ni, Cu, or Zn):: Synthesis and crystal structures

New compounds, In(3)Ti(2)AO(10) (A: Al, Cr, Mn, Fe, or Ga) and In6Ti6BO22 (B: Mg, Mn, Co, Ni, Cu, or Zn) were synthesized at and above 1000 degrees C in air through solid-state reactions among the constituent cation oxide powders. They are isostructural with the monoclinic and/or orthorhombic In3Ti2FeO10 having a pyrochlore-related crystal structure with a commensurate or incommensurate modulated structure. The high-temperature phase is orthorhombic, and the low-temperature phase is monoclinic. The lattice constants of In(3)Ti(2)AO(10) are as follows: In3Ti2AlO10 (1200 degrees C): a(Angstrom)= 5.833(2), b(Angstrom)= 3.371(2), and c(Angstrom) = 12.060(6); In3Ti2AlO10 (1100 degrees C): a(Angstrom) = 5.8368(7), b(Angstrom) = 3.3721(4), c(Angstrom) = 6.3402(8), and beta(degrees) = 107.87(1); In3Ti2CrO10 (1200 degrees C): a(Angstrom) = 5.9246(8), b(Angstrom) = 3.3562(5), c(Angstrom) = 6.3546(9), and beta(degrees) = 108.10(1); In3Ti2GaO10 (1200 degrees C): a(Angstrom) = 5.861(2), b(Angstrom) = 3.385(1), and c(Angstrom) = 12.094(4); In3Ti2GaO10 (1000 degrees C): a(Angstrom) 5.8742(9), b(Angstrom) = 3.3828(5), c(Angstrom) = 6.353(1), and beta(degrees) = 107.87(1). In3Ti2AlO10 and In3Ti2GaO10 are polymorphic. The lattice constants of In6Ti6BO22 are as follows: In6Ti6MgO22 (1200 degrees C): a(Angstrom) = 5.9236(7), b(Angstrom) = 3.3862(4), c(Angstrom) = 6.3609(7), and beta(degrees) = 108.15(1); In6Ti6MnO22 (1200 degrees C): a(Angstrom) = 5.9361(9), b(Angstrom) = 3.4031(5), c(Angstrom) = 6.3435(10), and beta(degrees) = 108.26(1); In6Ti6CoO22 (1200 degrees C): a(Angstrom) = 5.9243(5), b(Angstrom) = 3.3841(3), c(Angstrom) = 6.3495(6), and beta(degrees) = 108.18(1); In6Ti6NiO22 (1200 degrees C): a(Angstrom) = 5.9191(6), b(Angstrom) = 3.3729(3), c(Angstrom) = 6.3568(6), and beta(degrees) = 108.13(1); In6Ti6CuO22 (1000 degrees C): a(Angstrom) = 5.916(2), b(Angstrom) = 3.379(1), and c(Angstrom) = 12.029(4); In6Ti6ZnO22 (1200 degrees C): a(Angstrom) = 5.9223(6), b(Angstrom) = 3.3830(3), c(Angstrom) = 6.3576(6), and beta(degrees) = 108.16(1). In6Ti6BO22 (B: Mg, Mn, Co, Ni, or Zn) are monoclinic and In6Ti6CuO22 is orthorhombic. Solid solutions mere synthesized in between In(3)Ti(2)AO(10) (A: Al, Cr, Mn, Fe, or Ga) and In6Ti6BO22 (B: Mg, Mn, Co, Ni, Cu or Zn), and their lattice constants mere determined. Temperature in the parenthesis means synthesis temperature, and all the lattice constants,were measured at room temperature. The relationship between the unit cells of In(3)Ti(2)AO(10), In6Ti6BO22, their solid solutions, and the constituent cation elements of A and B are discussed in terms of their tendency for site preference. (C) 1999 Academic Press.