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International audience; The Aurivillius layered compounds with predominant fraction of paramagnetic transition metals are an emerging playground for discovery of magnetoelectric or multiferroic compounds. This aim was recently achieved by incorporating Fanions in the perovskite layer of the (Bi2O2)(CoF4) compound, only described so-far in a disordered model (unit cell : ap, ap, c). Here we report the investigation on the representative compounds (Bi2O2)(MF4) (M = Fe, Ni) using single crystal, synchrotron, neutron and electron diffraction. These reveal that the crystallographic average cell (2xap, 2xap, c) is orthorhombic, polar and accompanied by versatile (in)commensurate modulations. The supercell model was fully refined for (Bi2-xO2)(FeF4) (q = (0, ½, 0)) in the P2111 polar space group with transverse Fe-displacements relative to q. Bi-deficiency is compensated by a mixed Fe 2.5+ valence, but, the ideal stoichiometry is preserved for (Bi2O2)(NiF4). Both compounds are antiferromagnetic below TN = 89 K (Fe) and 45 K (Ni) with moments lying in the (ac) plane and a weak ferromagnetic component along the b-axis. DFT calculations validate a strongly anisotropic distribution of magnetic exchanges (Jab/Jc > 10). A broad anomaly on the dielectric constant at TN and a polarization loop at room temperature were obtained on (Bi2-xO2)(FeF4) single crystals, revealing multiferroism with magneto electric couplings.

The polar magnetic chalcogenide phase Ba

Mixed-anion compounds are among the most promising systems to design functional materials with enhanced properties. In particular, heteroleptic environments around transition metals allow tuning of the polarity or band-gap engineering for instance. We present the original oxysulfide Ba

Mixed-anion compounds are among the most promising systems to design functional materials with enhanced properties. In particular, heteroleptic environments around transition metals allow tuning of the polarity or band-gap engineering for instance. We present the original oxysulfide Ba5(VO2S2)2(S2)2, the fifth member in the quaternary system Ba–V–S–O. It exhibits the mixed-anion building units V5+O2S2 and isolated disulfide pairs (S2)2–. The structure is solved by combining single-crystal and powder X-ray diffraction and transmission electron microscopy. First-principles calculations were combined in order to highlight the anion roles. In particular, our density functional theory study shows that the 3p states of the disulfide pairs dictate the band gap. In this study, we point out anionic tools for band-gap engineering that can be useful for the design of phases for numerous applications. Finally, third harmonic generation (THG) was measured and compared to the large THG observed for Cu2O, which reveals the potential for nonlinear-optical properties that should be further investigated. 59;9

International audience; Rechargeable magnesium batteries are promising candidates for next-generation electrochemical energy storage, but their development is severely hindered by sluggish solid-state diffusion and significant desolvation penalties of the divalent cation. Studies suggest that nano-sized electrode materials alleviate these issues by shortening diffusion lengths and increasing electrode/electrolyte interaction. Here, the effect of particle size and synthetic methodology on the electrochemical performance of four sulfide cathode materials in Mg batteries is investigated: layered TiS2, CuS, spinel Ti2S4, and CuCo2S4. In these sulfide hosts, the direct preparation of nano-dimensional crystallites is critical to activate or improve electrochemistry. Even promising cathode materials can appear electrochemically inert when micron-sized particles are investigated (e.g., CuCo2S4), and mechanical milling leads to surface degradation of active material which severely limits performance. However, nano-sized CuCo2S4 prepared directly reaches a capacity nearly double that of ball-milled material and delivers 350 mAh g−1 at 60 °C. This work provides synthetic considerations which may be crucial in the discovery and design of novel Mg cathode materials, so that promising candidates are not overlooked. By extension, in oxide materials where Mg2+ diffusion is expected to be much more sluggish, this factor is anticipated to be even more important when screening for new hosts.

International audience; The possibility to use bilayer electrolytes based on bismuth oxide conductors should lead to a drastic decrease of solid oxide fuel cell (SOFC) operation temperature and calls for a reevaluation of some of the parameters optimized for high temperature applications. In this work we reinvestigate the promising La1-xSrxMnO3/Bi1.5Er0.5O3 (LSM/ESB) composite electrodes, varying the strontium content from x ~ 0.2, the typical high temperature LSM composition, to evaluate the optimum composition. Increasing the strontium content up to x 1⁄40.4–0.5 leads to a 14% decrease of the activation energy, resulting in a 50% decrease in the polarization resistance of symmetric cells at 500 °C compared to the traditional La0.85Sr0.15MnO3 composition with similar microstructure. The electrode performance is deteriorated by further increase in the strontium content. Based on surface composition, investigated by low energy ion scattering, we show that the SrO surface segregation pro­posed as the main deterioration mechanism for LSM based HT-SOFC is not an issue below 800 °C. Furthermore, we propose that the increase in performance is related to the decrease of cationic vacancies in LSM observed for high strontium content, which may help the oxygen dissociation and surface transport.

Magnesium batteries are an energy storage system that potentially offers high energy density, but development of new high voltage cathode materials and understanding of their electrochemical mechanism are critical to realize its benefits. Herein, we synthesize the layered MnO2 polymorph (the birnessite phase) as a nanostructured phase supported on conductive carbon cloth and compare its electrochemistry and structural changes when it is cycled as a positive electrode material in a Mg-ion battery under nonaqueous or aqueous conditions. X-ray photoelectron spectroscopy and transmission electron microscopy studies show that a conversion mechanism takes place during cycling in a nonaqueous electrolyte, with the formation of MnOOH, MnO, and Mg(OH)2 upon discharge. In aqueous cells, on the other hand, intercalation of Mg2+ ions takes place, accompanied by expulsion of interlayer water and transformation to a spinel-like phase as evidenced by X-ray diffraction. Both systems are structurally quasireversible. The ...

Magnesium batteries are energy storage systems that potentially offer high energy density owing to their ability to employ magnesium metal as a negative electrode. Their development, however, has been thwarted by a paucity of functional positive electrode materials after the seminal discovery of the Mo6S8 Chevrel phase over 15 years ago. Herein, we report the second such material – a thiospinel – and demonstrate fully reversible Mg2+ electrochemical cycling vs. a Mg anode, which is complemented by diffraction and first principles calculations. The capacity approaches 80% of the theoretical value at a practical rate (C/5) at 60 °C, and yields a specific energy of 230 Wh kg−1, twice that of the Chevrel benchmark. Our results emphasize the advantage in employing “soft” anions to achieve practical divalent cation mobility.

Batteries based on sodium layered transition metal oxides are a promising alternative to current state-of-the-art lithium-ion systems for large-scale energy storage, resulting in recent intensive efforts to develop high-energy density, low cost, stable cathode materials. Some of the most promising degrade on exposure to ambient atmosphere; however, the process is not understood. Here, using neutron/X-ray diffraction coupled with mass spectroscopy and thermal analysis, we reveal the nature of the reactivity. We demonstrate the unprecedented insertion of carbonate ions in the vacancy-rich layered structure of P2-Na0.67[Mn0.5Fe0.5]O2 on exposure to CO2 and moisture, concomitant with oxidation of Mn(III) to Mn(IV). The material exhibits much higher charge/discharge polarization and lower capacity than rigorously air-protected P2-Na0.67[Mn0.5Fe0.5]O2; a detailed study by online electrochemistry mass spectroscopy reveals that the inserted carbonate ions decompose during electrochemical charging, accounting for ...

Energy storage technology has received significant attention for portable electronic devices, electric vehicle propulsion, bulk electricity storage at power stations, and load leveling of renewable sources, such as solar energy and wind power. Lithium ion batteries have dominated most of the first two applications. For the last two cases, however, moving beyond lithium batteries to the element that lies below-sodium-is a sensible step that offers sustainability and cost-effectiveness. This requires an evaluation of the science underpinning these devices, including the discovery of new materials, their electrochemistry, and an increased understanding of ion mobility based on computational methods. The Review considers some of the current scientific issues underpinning sodium ion batteries.

Fortschrittliche Energiespeichertechnologien sind von immenser Bedeutung fur tragbare elektronische Gerate, Elektrofahrzeuge, die Stromspeicherung in Kraftwerken und den Lastausgleich von Stromnetzen auf der Basis erneuerbarer Energien wie Solarenergie und Windkraft. Fur die ersten zwei dieser Anwendungen haben sich Lithiumionenbatterien erfolgreich bewahrt. Fur die zwei letzteren Falle scheint es jedoch sinnvoll, einen Schritt weiterzugehen – hin zum nachsten Alkalimetall im Periodensystem, dem Natrium. Eine flachendeckende Einfuhrung von Natriumionenbatterien erfordert deren intensive Erforschung, einschlieslich der Entdeckung neuer Materialien und ihrer Elektrochemie. Dieser Aufsatz fasst den aktuellen Stand der Forschung auf dem Gebiet der Natriumionenbatterien zusammen.

A combination of operando X-ray diffraction, pair distribution function (PDF) analysis coupled with electrochemical measurements and Mossbauer spectroscopy elucidates the nature of the phase transitions induced by insertion and extraction of sodium ions in P2-Na0.67[NiyMn0.5+yFe0.5−2y]O2 (y = 0, 0.10, 0.15). When phase transitions are avoided, the optimal cathode material – P2-Na0.67Fe0.2Mn0.65Ni0.15O2 – delivers 25% more energy than the unsubstituted material, sustaining high specific energy (350 Wh kg−1) at moderate rates and maintains 80% of the original energy density after 150 cycles – a significant improvement in performance vs. the unsubstituted analogue. The crystal structure of the high voltage phase is solved for the first time by X-ray PDF analysis of P2-Na0.67−zFe0.5Mn0.5O2 (where z ∼ 0.5), revealing that migration of the transition metals – particularly Fe3+ – into tetrahedral sites in the interlayer space occurs at high potential. This results in new short range order between two adjacent layers. Although the transition metal migration is reversible as proven by electrochemical performance, it induces a large disfavourable cell polarization. The deleterious high voltage transition is mitigated by substitution of Fe3+ by Mn4+/Ni2+, giving rise to better cycling performance. Moreover, as demonstrated by 57Fe Mossbauer spectroscopy, the much lower ratio of Fe4+O6 to Fe3+O6 observed systematically across the range of Ni content – compared to the values expected from a purely ionic model – suggests redox activity involves the O-2p orbitals owing to their overlap with the transition metal-3d orbitals.

Synchrotron irradiation of the oxide YBaFe4O7.0 below 190 K converts the low temperature monoclinic structure to a higher symmetry tetragonal form analogous to the room temperature structure. This photo-induced metastable tetragonal form is stable even in the absence of irradiation over the range 4–60 K, however, above 60 K the photo-transition is reversible. These structural phenomena are correlated to the magnetic behaviour of this system, suggesting possible spin-lattice coupling. A scenario explaining the low temperature photo-induced transition is proposed, based on the different distributions of the valence electrons in the iron sub-lattice of the monoclinic and tetragonal phases.

The possibility to lift the geometric frustration in the “114” stoichiomeric tetragonal oxide YBaFe4O7.0 by decreasing the temperature has been investigated using neutron and synchrotron powder diffraction techniques. Besides the structural transition from tetragonal to monoclinic symmetry that appears at TS=180 K, a magnetic transition is observed below TN=95 K. The latter corresponds to a lifting of the 3D geometric frustration toward an antiferromagnetic long range ordering, never observed to date in a cubic based “114’” oxide. The magnetic structure, characterized by the propagation vector k1=(0,0,½), shows that one iron Fe2 exhibits a larger magnetic moment than the three others, suggesting a possible charge ordering according to the formula YBaFe 3 + Fe 3 2 + O 7.0 . The magnetic M(T) and χ′(T) curves, in agreement with neutron data, confirm the structural and magnetic transitions and evidence the coexistence of residual magnetic frustration. Moreover, the transport measurements show a resistive transition from a thermally activated conduction mechanism to a variable range hopping mechanism at TS=180 K, with a significant increase of the dependence of the resistivity vs. temperature. Mossbauer spectroscopy clearly evidences a change in the electronic configuration of the iron framework at the structural transition as well as coexistence of several oxidation states. The role of barium underbonding in these transitions is discussed.

The well-known all phenyl complex (APC) electrolyte for magnesium batteries is studied for the first time at high temperature using tetraglyme as a solvent. Combined with a molybdenum current collector, this enables the examination of positive electrode materials for Mg batteries at temperatures as high as 180 °C and up to 2 V vs. Mg, allowing discovery of the auspicious properties of CuS as a conversion cathode.

Although non-aqueous Li-ion batteries possess significantly higher energy density than their aqueous counterparts, the latter can be more feasible for grid-scale applications when cost, safety and cycle life are taken into consideration. Moreover, aqueous Zn-ion batteries have an energy storage advantage over alkali-based batteries as they can employ Zn metal as the negative electrode, dramatically increasing energy density. However, their development is plagued by a limited choice of positive electrodes, which often show poor rate capability and inadequate cycle life. Here we report a vanadium oxide bronze pillared by interlayer Zn2+ ions and water (Zn0.25V2O5⋅nH2O), as the positive electrode for a Zn cell. A reversible Zn2+ ion (de)intercalation storage process at fast rates, with more than one Zn2+ per formula unit (a capacity up to 300 mAh g−1), is characterized. The Zn cell offers an energy density of ∼450 Wh l−1 and exhibits a capacity retention of more than 80% over 1,000 cycles, with no dendrite formation at the Zn electrode. High-performing positive electrode materials are crucial for the development of aqueous Zn-ion batteries. Here the authors report a battery based on reversible intercalation of Zn ions in a layered Zn0.25V2O5⋅nH2O-based positive electrode, which exhibits high-capacity and long-term cycling stability.

The major advantage of Mg batteries relies on their promise of employing an Mg metal negative electrode, which offers much higher energy density compared to graphitic carbon. However, the strong coulombic interaction of Mg2+ ions with anions leads to their sluggish diffusion in the solid state, which along with a high desolvation energy, hinders the development of positive electrode materials. To circumvent this limitation, Mg metal negative electrodes can be used in hybrid systems by coupling an Li+ insertion cathode through a dual salt electrolyte. Two "high voltage" Prussian blue analogues (average 2.3 V vs Mg/Mg2+; 3.0 V vs Li/Li+) are investigated as cathode materials and the influence of structural water is shown. Their electrochemical profiles, presenting two voltage plateaus, are explained based on the two unique Fe bonding environments. Structural water has a beneficial impact on the cell voltage. Capacities of 125 mAh g-1 are obtained at a current density of 10 mA g-1 (≈C/10), while stable performance up to 300 cycles is demonstrated at 200 mA g-1 (≈2C). The hybrid cell design is a step toward building a safe and high density energy storage system.

The exploration of the phase diagram of the ferrite YBaFe{sub 4}O{sub 7+{delta}} versus the oxygen content {delta} and temperature shows the complex crystal chemistry of this system. Besides the cubic form (F4 Macron 3m), which is observed up to 600 Degree-Sign C and for 0

The study of the oxidation of the “114” orthorhombic cobaltite CaBaCo4O7, using first electrochemistry and then soft chemistry based on oxidation by NaClO, has allowed a new phase, CaBaCo4O7.50, to be prepared topotactically. The structural study of this phase shows that its hexagonal structure, closely related to that of orthorhombic CaBaCo4O7, is curiously similar to that of the members of the LnBaCo4O7 series, in spite of its excess oxygen. Its magnetic study shows that this phase, like CaBaCo4O7, is ferrimagnetic with the same TC (60 K), but differently exhibits an unusual magnetic hysteresis. This exceptional behavior of CaBaCo4O7 with respect to oxidation as well as the magnetic properties of CaBaCo4O7.50 is interpreted in terms of the presence of defects due to oxidation.

Energy storage technology has received significant attention for portable electronic devices, electric vehicle propulsion, bulk electricity storage at power stations, and load leveling of renewable sources, such as solar energy and wind power. Lithium ion batteries have dominated most of the first two applications. For the last two cases, however, moving beyond lithium batteries to the element that lies below-sodium-is a sensible step that offers sustainability and cost-effectiveness. This requires an evaluation of the science underpinning these devices, including the discovery of new materials, their electrochemistry, and an increased understanding of ion mobility based on computational methods. The Review considers some of the current scientific issues underpinning sodium ion batteries.

A disordered rock-salt-type structure Li2VO3, a cathode material for Li ion batteries, is easily formed through lithium insertion into LiVO3.

Title compounds with Ln: Dy, Ho, Er, Tm, Yb, and Lu are synthesized from stoichiometric mixtures of Ln2O3, BaFe2O4, Fe2O3, and Fe (1100 °C, 24 h) and from solutions of Ln2O3, BaCO3, and Fe(C2O4) in molten citric acid, followed by calcination (900 °C for 6 h and 1050 °C for 24 h).

Stoichiometric LnBaFe4O7.0 oxides with Ln = Dy to Lu have been synthesized and protected in order to prevent oxidation at room temperature. The structural study of these compounds, using laboratory and synchrotron X-ray as well as neutron powder diffraction, shows the extraordinary flexibility of the tetrahedral [Fe4] sublattice of these compounds, which exhibit various distortions. At room temperature they all are tetragonal (I4), and at higher temperature (T580 K) they exhibit a cubic symmetry (F43m). Moreover, the low-temperature structures of these oxides are dependent on the nature of the Ln(3+) cation. At 110 K, compounds with Ln = Dy and Ho adopt the same monoclinic (P12(1)1) structure as YBaFe4O7.0, whereas YbBaFe4O7.0 possesses a new centered monoclinic cell (I121), and members with Ln = Er and Lu keep the tetragonal (I4) symmetry. Neutron diffraction patterns evidence long-range magnetic ordering only for the most distorted structures (Ln = Dy and Ho), showing that the geometric frustration generated by the tetrahedral [Fe4]∞ sublattice can be lifted only with the most severe distortions. The other oxides (Ln = Er, Yb, and Lu) with weakly distorted [Fe4]∞ sublattices do not exhibit magnetic ordering down to 4 K, demonstrating the importance of magnetic frustration. The behavior of these "114" iron oxides is compared to the cobalt family, showing in both cases a striking underbonding of barium.

Mg batteries have received attention as a potential candidate for energy storage. The main attraction relies on the use of a Mg negative electrode, which is inexpensive, safe to handle and store, and offers high volumetric energy density together with dendrite free deposition during electrochemistry processes.(1) However, sluggish Mg2+ diffusion in most solid structures has hindered development of the positive electrode material, and thus the entire system. Nevertheless, this issue can be addressed by coupling the Mg negative electrode with a Li insertion positive electrode through a dual-salt electrolyte, so that the advantages of the Mg anode is preserved and facile monovalent cation diffusion in the positive electrode is accomplished.(2) In this presentation, we will discuss two Mg-Li hybrid batteries that employ Prussian Blue analogues (PBA) with different water contents – Fe[Fe(CN)6]0.95·2.3H2O (23-PBA) and Fe[Fe(CN)6]0.95·0.7H2O (07-PBA) – as the positive electrode materials in the all phenyl complex (APC) (3) + LiCl dual salt electrolyte (Figure 1a). The PBA was specifically chosen due to its open tunnels in the crystal structure that provide various ion pathways, as well as robust Fe-CN bonds which ensure a high resistance to chlorine corrosion due to the electrolyte. The materials were tested at a current density of 10 mA g-1 (~ C/10, 1C = 1e-/PBA f.u.), resulting in ~ 130 mAh g-1 specific capacities for both PBAs. Two well defined voltage plateaus were observed at 2.6/2.0 V (vs. Mg) for 23-PBA and 2.3/2.0 V for 07-PBA (Figure 1b), associated with the two distinct Fe cations bound to C and N, respectively. The higher voltage observed for 23-PBA resulted from the additional stability of the lithiated phase resulting from coordinating the inserted Li+ with structural water. The ± 0.1 V voltage for metal stripping/plating on the Mg negative electrode (Figure 1b inset) suggests that the reduction of Li+, which would typically commence at -0.7 V, did not occur. Coulombic efficiency of 99% up to 300 cycles for 07-PBA was observed, in contrast to the much poorer performance of 23-PBA (Figure 1c). The lower capacity retention of 23-PBA originated from its structural water which remained in the material during the first cycle but dissolved into the electrolyte upon prolong cycling, as proven by ex-situ FT-IR. The detailed Li+ insertion mechanism was studied by in-situ XRD, where similar results were obtained for both materials. A decrease of cell parameter was observed on the higher voltage plateau, resulting from the additional electrons introduced to the Fe-C bonding orbital. At the beginning of the lower voltage plateau, phase separation occurred but the following charge illustrated the reversibility of the entire process that represents excellent reversibility of Li+de/intercalation into the structure. Even after prolonged cycling in the hybrid cell, a dendrite free surface was obtained on the Mg negative electrode, indicating a very different electrodeposition process is prevalent compared to that of Li metal. As such, the primary advantages of the Mg negative electrode are preserved. Thus, the Mg-Li hybrid system with a PBA positive electrode provides a new direction to explore “high voltage” Mg batteries. Other promising positive electrode Mg2+insertion materials will be also discussed in our presentation that do not rely on the hybrid concept. References: (1) H. D. Yoo, I. Shterenberg, Y. Gofer, G. Gershinsky, N. Pour and D. Aurbach, Energy Environ. Sci. 6, 2265 (2013). (2) S. Yagi, T. Ichitsubo, Y. Shirai, S. Yanai, T. Doi, K. Murase and E. Matsubara, J. Mater. Chem. A 2, 1144 (2014). (3) O. Mizrahi, N. Amir, E. Pollak, O. Chusid, V. Marks, H. Gottlieb, L. Larush, E. Zinigrad and D. Aurbach, J. Electrochem. Soc. 155, A103 (2008). Figure 1

The title compound is prepared by solid state reaction of a stoichiometric mixture of BaFe2O4, Fe2O3, Y2O3, and metallic Fe (sealed silica tube, 1100 °C, 24 h).

The title compound is obtained by oxidation of CaBaCo4O7 either electrochemically in alkaline medium or by reaction with an aqueous solution of NaClO.

A new polyoxometalate-based organic–inorganic platform has been designed for further facile derivatization and covalent attachment of organic linkers; this is exemplified by the grafting of a polypyridyl ligand.

Multivalent-ion chemistries such as Mg-ion are emerging as alternative battery systems to Li-ion. Current Mg-ion chemistries are limited to relatively low voltages and relatively low reversible specific capacities (1-2). Recent research on potential high voltage Mg-ion cathode materials and alternative anode materials such as transition metal oxides and metal alloys have highlighted the urgent need to understand structure activity relationships and insertion/intercalation phenomenon for development of such systems (3). Solid state NMR is a powerful tool to investigate local structure and insertion/intercalation phenomena, particularly for batteries as shown for Li-ion chemistries with 6Li and 7Li NMR (4, 5). However, the low natural abundance (10%) of the NMR active Mg isotope (25Mg), highly quadrupolar nuclear spin of 25Mg (spin 5/2) and very low gyromagnetic ratio (i.e 30.6 MHz Larmor frequency relative to 1H = 500 MHz) limits the effective use of 25Mg NMR for solid Mg-ion battery materials (6). In this work, despite the challenges of 25Mg NMR, our recent efforts to characterize Mg environments in cathode materials such as MgMn2O4 spinels, MgV2O5, in anode materials such as h-TiO2 and Mg-Sn alloys will be presented. Chemical magnesiation using dibutylmagnesium and preliminary electrochemical (de)mangesiation and the structral changes induced will be discussed. The results will summarize the effectiveness of the method in distinguishing side reactions or undesirable conversion reactions, including amorphous phases, from intercalation phenomenon. References: 1. D. Aurbach, Z. Lu, A. Schechter, Y. Gofer, H. Gizbar, R. Turgeman, Y. Cohen, M. Moshkovich, and E. Levi, Nature, 407 (6805), 724-727 (2000). 2. H. D. Yoo, I. Shterenberg, Y. Gofer, G. Gershinsky, N. Pour, and D. Aurbach, Energ Environ Sci, 6 (8), 2265-2279 (2013). 3. Magnesium Batteries 1 and 2, 224th Electrochemical Society Meeting, San Francisco CA, 2013 4. C. P. Grey and N. Dupre, Chem. Rev. (Washington, DC, U. S.), 104, 4493 (2004). 5. B. Key, R. Bhattacharyya, M. Morcrette, V. Seznec, J. M. Tarascon and C. P. Grey, Journal of the American Chemical Society, 131, 9239 (2009). 6. R. Dupree and M. E. Smith, Journal of the Chemical Society-Chemical Communications, 1483 (1988).

The study of the ferrites YBaFe4−xMnxO7 shows that the substitution of Mn2+ for Fe2+ in YBaFe4O7 stabilizes the hexagonal symmetry at the expense of the cubic one for 1 ≤ x ≤ 2. Using combined measurements of a.c. and d.c. magnetization, we establish that Mn substitution for Fe in YBaFe4O7 leading to a cationic disorder induces a spin glass behaviour. An important characteristic of these Mn substituted ferrites deals with their ability to absorb and desorb reversibly oxygen, leading to the oxides YBaFe4−xMnxO7+δ, with the highest δ values 2–2.25 that have been observed to date in this “114” family. These oxidized “Mn ferrites” keep the hexagonal symmetry and the spin glass characteristic temperature, Tsg, is varying with the oxygen content δ.