Fluorine insertion reactions of the brownmillerite materials Sr2Fe2O5, Sr2CoFeO5, and Sr2Co2O5

Synthesis, structural and magnetic characterisation of the fully fluorinated compound 6H–BaFeO2F

“…In the perovskite structure, the AX 3 subsystem forms a close packed lattice, where the stacking sequence can differ [4] from purely cubic (c… e. g. for SrFeO 2 F [5][6][7][8][9] and BaFeO 2 F [7,[10][11][12] (both space group Pm3m)) to purely hexagonal (h… e. g. for BaCoO 3 [13]) and can also form lattices in between those two extremes (e. g.…”

Anion Doping of Ferromagnetic Thin Films of La0.74Sr0.26MnO3−δ via Topochemical Fluorination

“…The contraction of the out-of-plane lattice parameter upon oxidation is not only known for manganites [31], but also for other perovskite-type compounds [32,33]. …”

“…can give a strong indication for which fluorination mechanism has taken place. This is explained by the empirical finding that the volume per formula unit mainly depends on the transition metal oxidation state and not on the detailed composition of oxygen and fluoride ions as well as vacancies of the anion sublattice [18,32,33,34] the higher the transition metal oxidation state, the smaller its ionic radius and the lower the volume per formula unit. This can be exemplified by the following: for the fluorination of SrFe 3+ O 2.5 and BaFe 3+ O 2.5 under formation SrFe 3+ O 2 F [32] and BaFe 3+ O 2 F [32,35] (0 ≤ 2x ≤ 1), i.e., corresponding to mechanism (b), the average change of the cubic (pseudocubic) lattice parameter is as low as 0.5% for the two end members (ΔV~1.5%).…”

“…This can be exemplified by the following: for the fluorination of SrFe 3+ O 2.5 and BaFe 3+ O 2.5 under formation SrFe 3+ O 2 F [32] and BaFe 3+ O 2 F [32,35] (0 ≤ 2x ≤ 1), i.e., corresponding to mechanism (b), the average change of the cubic (pseudocubic) lattice parameter is as low as 0.5% for the two end members (ΔV~1.5%). In contrast, the fluorination of SrFeO 3 to SrFeO 2 F (mechanism (a) goes with a strong increase of the unit cell (ΔV~+6%) [32,36], whereas the fluorination of brownmillerite compounds AMO 2.5 to AMO 2.5 F 0.5 (mechanism (c)) is accompanied by a strong shrinkage of the unit cell [33,34]. The maintenance of the unit cell volume therefore strongly indicates a substitutive fluorination according to mechanism (b).…”

Magnetic, optical, microscopic and electrical behavior of Ca2−xYxCo2O5 prepared by a molten flux method

“…It also proved as a promising candidates in the area of advanced microelectronic, optoelectronic, and spintronic devices [1,2]. Thermoelectric materials play an important role in electric power generation in terms of waste heat recovery as well as the refrigeration of electronic devices.…”