Growing of single-crystals of double sodium-manganese(II) pyrophosphate

Abstract

Single crystals of Na2Mn3(P2O7)2 compound have been first obtained during the examination of interaction in the Na2O–P2O5–Mn2O3–NaF (10 wt.%.) system in the fluxes with Na2O:P2O5 molar ratios ranging from 0.52 to 0.76 (saturated with manganese(III) oxide 25.0–32.0 wt.%) at the temperatures of 960–8800С. Optimum conditions for the synthesis and growing of single crystals of Na2Mn3(P2O7)2 compound have been determined. Complete X-ray diffraction analysis of the synthesized phosphate Na2Mn3(P2O7)2 has been performed. According to its structure, the double phosphate Na2Mn3(P2O7)2 belongs to the triclinic crystal system, spatial grid P ; lattice parameters are as follows: a=5.359 Å, b=6.563 Å, c=16.299 Å, =81.290, =82.700, =72.440, V=538.23 Å3, Z=4, сcalc= 3.447 g cm–3. Structural features of synthesized phosphate have been determined. The structure is composed of continuous chain of distorted octahedra [MnO6] spacing along the direction ob. Diphosphate groups of tetrahedra [РО4] divide the chains [MnO6] and also run along ob direction. Pairwise linked pentagonal bipyramids of sodium divide the "units" of polyhedral of manganese and phosphorus, filling the channels along oy axis. The crystalline structure of Na2Mn3(P2O7)2 includes three nonequivalent, according to their crystallography, octahedra of manganese with slightly distorted form. The compound has been studied using X-ray diffraction and X-ray phase analyses, differential thermal analysis, IR spectroscopy and complete chemical analysis.