The effects of Mn substitution on the structural and magnetic properties of the NASICON-type Na3Fe2

Crystal Structures and Local Environments of NASICON-Type Na3FeV(PO4)3 and Na4FeV(PO4)3 Positive Electrode Materials for Na-Ion Batteries

“…The spectrum of Na 3 FeV­(PO 4 ) 3 supports the successful synthesis of a pure phase, the quadrupole doublet accounting for 97(3) % of the total Fe amount, despite a very tiny contribution [3(3) %] being associated to a partial reduction of Fe III into Fe II . The Mössbauer parameters describing the main signal are typical of high-spin Fe III in an octahedral environment with oxygen surrounding it. , The Mössbauer spectra of electrochemically sodiated samples clearly show the reduction of Fe III to Fe II without any impurity signal. The spectrum of Na 4 FeV­(PO 4 ) 3 (sample C) indicates the main doublet associated with Fe II corresponding to at least 87(3) % of the total Fe amount.…”

“…The Mössbauer parameters describing the main signal are typical of high-spin Fe III in an octahedral environment with oxygen surrounding. 52,53 The Mössbauer spectra of electrochemically sodiated samples clearly show According to DSC data (Figure 6a), two reversible phase transitions are indeed observed for Na 3 FeV(PO 4 ) 3 at around 89.4 °C and 123.2 °C during heating, the specific heat capacity of the first phase transition (4.0 J/g) being much higher than that of the second one (0.7 J/g). In situ temperature XRD measurements further confirm the order-disorder phase transitions.…”

“…The Mossbauer parameters describing the main signal are typical of high-spin Fe III in an octahedral environment with oxygen surrounding it. 52,53 The Mossbauer spectra of electrochemically sodiated samples clearly show the reduction of Fe III to Fe II without any impurity signal. The spectrum of Na 4 FeV(PO 4 ) 3 (sample C) indicates the main doublet associated with Fe II corresponding to at least 87(3) % of the total Fe amount.…”

An Asymmetric Sodium Extraction/Insertion Mechanism for the Fe/V-Mixed NASICON Na4FeV(PO4)3

“…They correspond to typical high-spin Fe 2+ or Fe 3+ in octahedral environments with oxygen ligands. 21,24,39,40 During the first domain of the charge process, Fe 2+ is fully oxidized to Fe 3+ associated with the extraction of the first Na + . After that, until the end of The quadrupole doublets that describe the spectra are associated with Fe 2+ (green), Fe 3+ (I) (light brown), and Fe 3+ (II) (dark brown).…”

Exploring the Role of Manganese on Structural, Transport, and Electrochemical Properties of NASICON-Na3Fe2–yMny(PO4)3–Cathode Materials for Na-Ion Batteries

“…In this paper, Na 3 Fe 2– y Mn y (PO 4 ) 3 NASICON materials with different contents of manganese substituted in the iron sub-lattice were proposed as cathode materials for NiBs. Manganese substitution had already been reported in other three-dimensional structures, such as alluaudites or triphylites , but, to the best of our knowledge, only two papers that confirm the formation of NASICON-Na 3 Fe 2– y Mn y (PO 4 ) 3 have been published thus far. , The present paper describes a facile solid-state synthesis method used to obtain Na 3 Fe 2– y Mn y (PO 4 ) 3 materials and the investigation of the structural, microstructural, and thermal properties for y = 0, 0.1, 0.2, 0.3, and 0.4. The impact of manganese substitution on the phase transitions and transport properties in Na 3 Fe 2– y Mn y (PO 4 ) 3 materials is discussed extensively.…”