Structural and Mössbauer studies of nanocrystalline Mn2+-doped Fe3O4 particles

Tunable Control of the Structural Features and Related Physical Properties of MnxFe3–xO4 Nanoparticles: Implication on Their Heating Performance by Magnetic Hyperthermia

“…Such hypothesis supports the low relative areas of the subspectra ascribed to Mn–wüstite in the Mössbauer data. Regarding the values found for the hyperfine parameters for Mn x Fe 3– x O 4 and Mn y Fe 1– x – y O, and particularly the isomer shift values, the results herein obtained are congruent with those reported for Mn-substituted ferrites − , and mangano-wüstite and with the above-discussed XPS data, which indicated that Mn atoms are found in the divalent state.…”

“…When Fe 2+ is progressively replaced by Mn 2+ , this last cation occupies preferentially the A sites due to its larger ionic radius, thus favoring, under equilibrium and bulk conditions, the formation of a near-normal spinel with an inversion parameter ( i ) of 0.2 . This also explains the changes of the inversion degree in the substituted Mn ferrites according to the different preparative routes of Mn x Fe 3– x O 4 . − In addition, the particle size reduction has also a relevant impact on the expected cation distribution between A and B sites . For Mn x Fe 3– x O 4 NPs, a partially inverse cation distribution has been reported, including a surface shell of disordered spins coupled through frustrated exchange interactions …”

“…The Mössbauer parameters corresponding to the fitting of these spectra are summarized in Table S2 of the Supporting Information. The spectral model to be fitted was decided considering (1) the spectra profile, (2) the information regarding the phase composition for these NPs, and (3) previous reported studies for analogue materials. ,− , From these facts, the model includes two Fe 3+ sextets and a weak Fe 2+ sextet for the Mn x Fe 3– x O 4 core. The Fe 3+ sextets present isomer shift (δ) values between 0.2 and 0.3 mm/s and zero quadrupole splitting (Δ), which is devoted to both the symmetric oxygen coordination environment around the metals and the symmetric distribution of electrons in the high spin d 5 configuration for these ions.…”

In Situ Fabrication of Electro-Fenton Catalyst from Fe2+ in Acid Mine Drainage: Influence of Coexisting Metal Cations

“…28,29 To prepare transition metal-doped Fe 3 O 4 , the most common method is the coprecipitation of highly pure predetermined amount of ferrous and selected transition metal salts, followed by thermal treatment. 30,31 In comparison, the AC-FC technology has provided an alternative approach for in situ fabricating cobalt-/ manganese-doped Fe 3 O 4 on the GF support. In particular, the electro-oxidation of Fe 2+ in the AC-FC makes the iron more easily loaded on the GF than other metal cations.…”

“…As a fact of matter, cobalt-/manganese-substituted iron oxides have been regarded as a promising class of heterogeneous Fenton catalysts . Once introduced into iron oxides, the transition metals cobalt and manganese not only change the active sites of Fe 3 O 4 for enhanced catalytic activity but also are directly involved in the oxidation process via their efficient role in activating H 2 O 2 . , To prepare transition metal-doped Fe 3 O 4 , the most common method is the coprecipitation of highly pure predetermined amount of ferrous and selected transition metal salts, followed by thermal treatment. , In comparison, the AC-FC technology has provided an alternative approach for in situ fabricating cobalt-/manganese-doped Fe 3 O 4 on the GF support. In particular, the electro-oxidation of Fe 2+ in the AC-FC makes the iron more easily loaded on the GF than other metal cations.…”