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

Abstract

The mixed-valent iron fluoride hydrate Fe,F5-7H,0 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 x 10-lo m, and cc = 105.81, p = 123.28, and y = 82.93". Thermal analysis shows that a t 75 "C in flowing nitrogen the heptahydrate loses water to form the dihydrate, Fe,Fs*2H,0.Further dehydration in nitrogen produces two phases (A and B) not previously reported and the two components FeF, and FeF,.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 x 1 0-lo m. Phase A is stable over a wider temperature range (1 90-400 "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 x 10-lo m. The components FeF, and FeF, 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 N, . 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.

Synthesis by Thermal Decomposition of Two Iron Hydroxyfluorides: Structural Effects of Li Insertion

“…The absence of the +19 signal indicates that the measured weight loss is only associated with the dehydration of Fe 2 F 5 (H 2 O) 2 . Moreover, the corresponding weight loss related to the dehydration process indicates a loss of 2 water molecules per formula unit as shown in reaction and in agreement with a previous study The thermal behavior of Fe 2 F 5 (H 2 O) was further investigated under ambient humid air and dry air (Figure b), showing noticeable differences as compared to N 2 .…”

“…Moreover, the corresponding weight loss related to the dehydration process indicates a loss of 2 water molecules per formula unit as shown in reaction 1 and in agreement with a previous study. 40 Fe…”

Moessbauer and magnetic studies of a mixed-valence ferrimagnet, pentafluorodiiron(II,III) dihydrate

“…Under these conditions, that same peak velocity is used in the calculation of isomer shifts and quadrupole splittings for both Fe2+ and Fe3+. Conversely, that peak position should be calculable from reported isomer shifts and quadrupole splittings according to velocity = + -"/2 (9) and should yield identical values of the peak velocity for both n = 2 and = 3. However, examination of the data from ref 10 and 11 shows that the peak positions calculated from the Fe2+ and Fe3+ parameters differ by 0.14 and 0.10 mm/s, respectively.…”

One-shot versus stepwise gas–solid synthesis of iron trifluoride: investigation of pure molecular F2 fluorination of chloride precursors

“…S2, ESI3) by solvothermal reactions, 26 or by synthesis in fluorinated ionic liquid. 33 Other hydrated forms of iron fluorides are Fe 2 F 5 ?7H 2 O (no ICSD, PDF(I) #00-045-0883), 34 Fe 2 F 5 ?2H 2 O (ICSD #1167 and 201737, PDF #00-049-1263, Fig. S5, ESI 3 ), [35][36][37] Fe 1.9 F 4.75 ?0.95H 2 O (no ICSD, PDF(B) #00-028-0483) 38 and Fe 3 F 8 ?2H 2 O (ICSD #37140 and 38366, Fig.…”