F. Abraham, O. Cousin, O. Mentré
Aug 1, 2002
Citations
0
Influential Citations
27
Citations
Journal
IEEE Journal of Solid-state Circuits
Abstract
Abstract The crystal structures of some recently published bismuth–transition metal oxy-phosphates are described as the association of complex infinite one-dimensional polycations and phosphate anions. The complex cations are built from oxygen-centered tetrahedra sharing edges to form infinite ribbons of n tetrahedra width. This structural concept allows one to describe the essential structural features of new highly disordered bismuth–transition metal oxy-phosphates, Bi ∼1.2 M ∼1.2 PO 5.5 ( M =Mn, Co, Zn). The new compounds have been synthesized and structurally characterized by single-crystal X-ray diffraction. The three compounds crystallize in the orthorhombic space group Ibam (No. 72), Z =8. The lattice parameters are a =15.079(2), b =11.247(2), c =5.437(1) A for M =Mn, a =14.752(3), b =11.205(3), c =5.434(2) A for M =Co and a =14.809(2), b =11.214(1), c =5.440(1) A for M =Zn. Because of a high disorder over several cationic sites, only an approach of the crystal structure determination has been achieved. Actually, the structure is characterized by perfectly defined ribbons parallel to the (010) plane and built from a central chain of edge-shared OBi 4 tetrahedra running along the c axis and linked by edges to two other edge-shared O(Bi, M ) 4 tetrahedra chains. The positions at the border of ribbons are randomly occupied by bismuth and M atoms. The formula of the three tetrahedra width ribbons is (O 3 Bi 2.4 M 1.6 ) +4.4 . The phosphate ions and M 2+ cations are disordered in the interspace between the ribbons.