Mixed-valent iron fluoride hydrates and their thermal-decomposition products

Publisher Website
Google Scholar
Abstract
The mixed-valent iron fluoride hydrate Fe2F5·7H2O has been confirmed by chemical and thermal analysis. The unit cell has been found by powder and single-crystal diffractometry to be triclinic with a= 6·582, b= 8·988, c= 10·542 × 10–10 m, and α= 105·81, β= 123·28, and γ= 82·93°. Thermal analysis shows that at 75 °C in flowing nitrogen the heptahydrate loses water to form the dihydrate, Fe2F5·2H2O. Further dehydration in nitrogen produces two phases (A and B) not previously reported and the two components FeF2 and FeF3. Phase B occurs in a very narrow temperature range, 190–230 °C, but gives sharp reflections which have been indexed according to the cubic unit cell, a= 10·37 × 1010 m. Phase A is stable over a wider temperature range (190–400 °C) and gives broadened lines in the X-ray Guinier-powder photograph. These have been indexed on the basis of the hexagonal unit cell, a= 6·40, c= 7·56 × 10–10 m. The components FeF2 and FeF3 first appear at ca. 250 °C and above 500 °C are the only crystalline phases present. The two dehydration steps in the decomposition of the heptahydrate occur at much lower temperatures in flowing HF than in N2. The first step also yields the dihydrate, but the second step gives an anhydrous product which contains a phase A′ with an X-ray pattern similar to that of A but no reflections of B are detected. No ferromagnetism is exhibited by any of the new phases.

This publication has 0 references indexed in Scilit: