Synthesis and ab initio Determination of Bi1.25 V0.123 Ca 0.245 N1.24 O8 cubic structure via powder X-ray diffraction data

Abstract

This paper deals with the ab initio structure determination of Bi1.25 V0.123 Ca 0.245 N1.24 O8 cubic structure from powder X-ray data using the Rietveld method, and with physical properties characterization of a related solid solution. Bi1.25 V0.123 Ca 0.245 N 1.24 O 8 obtained from the annealing of a quenched cubic high temperature of sample, is cubic crystal system and lattice a=14.1243 Å; Z =4. The structure refinement converged to Rp=0.018, R wp=0.0212 GOF=0.0102. The structure is built from cationic slabs parallel to (100) faces of the cubic cell. Each cell corresponds to one slab containing a mixed Bi1.25 V0.123 Ca 0.245 cationic layer (Bi(1)) sandwiched between two equivalent bismuth layers (Bi(2)). The cohesion of the cations in the slabs results from the presence of the oxygen atoms and nitrogen atoms distributed over three sites. Six O(1) and two O(2) atoms form a slightly distorted cubical polyhedron around the mixed cationic site (Bi(1)). (Bi(2)) atoms are surrounded by seven oxygen nitrogen atoms in a very distorted polyhedron. The important delocalization of (Bi(2)) lone pairs toward the integers spaces leads to significant bonds with the adjacent slabs and to the cohesion of the structure. Bi1.25 V0.123 Ca 0.245 O8 is the low symmetry variety of a particular sample of a wide solid solution domain that, formulated Bi1.25 V0.123 Ca0.245 O8, has been investigated. The formation of this phase from the irreversible transformation of quenched on heating and the subsequent transitions and non-transition metal oxides mixed valence have been evidenced by thermo diffractometry, conductivity measurements versus temperature, dilatometer, and thermal analyses. The morphological study was carried out by SEM.