Modulated structure of the pseudohexagonal InFe(1--x--4 delta)Ti(x+3 delta)O(3+x/2) (x = 0.61) composite crystal.

The structure of pseudohexagonal-type InFe(1--x--4 delta)Ti(x+3 delta)O(3+x/2) (x = 0.61, delta = 0.04), indium iron titanium oxide, was refined on the basis of a four-dimensional superspace group. The crystal has a compositely modulated structure consisting of two orthorhombic subsystems mutually incommensurate in b. The first subsystem InFe(1-x-4 delta)Ti(x+3 delta)O(2) has a delafossite structure with lattice parameters a = 5.835 (3), b(1) = 3.349 (1) and c = 12.082 (7) A. The second subsystem with b(2) = 2.568 (6) A consists of O atoms. The superspace group of the overall structure is Ccmm(1, 1.305, 0)s00, which can be converted to Amam(0, 0, 0.305)0s0 (No. 63.8). Refinement on 1105 unique reflections converged to R = 0.0303 and wR = 0.0325 with 63 structural parameters. The structure of the first subsystem is the alternate stacking of an edge-shared InO(6) octahedral layer and an Fe/Ti triangle-lattice plane along c. A sheet of O atoms in the second subsystem is also extending on the Fe/Ti plane, where displacive modulation of atoms is prominent.