The crystal structure of a bimuth–transition metal phosphate Bi 6TiP 2O 16

Abstract

A single-crystal was selected from the reaction product of a stoichiometric mixture of Bi 3PO 7 to which was added 10% TiO 2 and its crystal structure determined from three-dimensional X-ray diffraction data. The structure is monoclinic, a=11.233(2) Å, b=5.410(1) Å, c=11.233(2) Å, β=95.13(3)°, space group I2, Z=2; least squares refinement was on F 2 and converged to R1=0.0514, w R2=0.146 for 833 unique reflections. The crystal was twinned by a 180° rotoinversion about the [ 1 ̄ 01] direction of the direct lattice, resulting in the interchange of the a and c axes. The structure consists of chains formed by edge sharing of OBi 4 tetrahedra. The stacking along [100] consists of these chains bridged by layers formed by TiO 6 octahedra and PO 4 tetrahedra. The three crystallographically independent Bi ions are surrounded by eight oxygen ions that form two bicapped trigonal prisms and one distorted cubic environment, respectively. The Bi–O distances vary from 2.20(4) to 3.16(4) Å. Ti is in octahedral environment in which the equatorial distances are 1.82(3) and 2.00(5) Å and the apical distances are 2.14(4) Å. The PO 4 tetrahedron is nearly regular.