Phase relations in the system K2MoO4-KPO3-MoO3-Bi2O3: A new phosphate K3Bi5(PO4)(6)

摘要

Phase equilibrium in the pseudo-quaternary system K2O-MoO3-P2O5-Bi2O3 was studied as three-component solvent K2MoO4- KPO3-MoO3 containing 15mol% Bi2O3 during slow cooling and spontaneous crystallization. The results of the investigation were shown on a composition diagram, which indicates the crystallization fields of K2Bi(PO4)(MoO4), K5Bi(MoO4)(4), BiPO4 and K3Bi5(PO4)(6). New phosphate K3Bi5(PO4)(6) was characterized by single-crystal X-ray diffraction (space group C2/c, a = 17.680(4), b = 6.9370(14), c = 18.700(4) angstrom, beta = 113.79(3)degrees) and FTIR spectroscopy. The possibility of lone electron pair stereoactivity of bismuth was suggested using the calculations of characteristics of the Voronoi-Dirichlet polyhedra for K3Bi5(PO4)(6) and K2Bi(PO4)(MoO4). (C) 2007 Elsevier Inc. All rights reserved.