Quadrupole Splitting Distributions in Purpurite and Related Minerals

Abstract

The quadrupole splitting distributions (QSDs) from the Mössbauer spectra of triphylite, ferrisicklerite and purpurite at 298 K and 80 K were obtained by the use of the Voigt-based quadrupole splitting distribution (QSD) method for the first time. QSDs of Fe 2+ and Fe 3+ are attributed to Fe 2+ and Fe 3+ at the corresponding octahedrally coordinated sites in the crystal structures of the three phosphate minerals. The influence on the distortion of the M2 site by different next-nearest neighbor (NNN) configurations was discussed based on the Jahn-Teller effect in purpurite, and the authors propose two M2 subsites with different distortions in purpurite. Two QSDs of Fe 3+ in the Mössbauer spectra of purpurite are tentatively assigned to Fe 3+ at the two M2 subsites, and next-nearest neighbor (NNN) effects were used to interpret the Mössbauer spectra of purpurite.

Operando57Fe Mössbauer and XRD investigation of LixMnyFe1-yPO4/C composites (y = 0.50; 0.75)

“…The new doublet corresponding to Fe 3+ phase Mn III 0:50 Fe III 0:50 PO 4 exhibits a quadrupole splitting of 1.65 mm s 21 , which is higher than 1.55 mm s 21 observed for Mn III 0:25 Fe III 0:75 PO 4 , and this further confirms that the Fe 3+ is very sensitive to the oxidation state of Mn since an increase of the amount of Mn 3+ around the Fe 3+ site leads to a significant increase of the quadrupole splitting. 31 Similar spectra have been reported for natural purpurite (Fe,Mn)PO 4 . 31 The electromechanism of the charge and discharge of LiMn 0.50 Fe 0.50 PO 4 /C is done in three steps as the LiMn 0.25 Fe 0.75 PO 4 /C phase.…”

“…31 Similar spectra have been reported for natural purpurite (Fe,Mn)PO 4 . 31 The electromechanism of the charge and discharge of LiMn 0.50 Fe 0.50 PO 4 /C is done in three steps as the LiMn 0.25 Fe 0.75 PO 4 /C phase. At the beginning, the mechanism is biphasic, with the coexistence of LiMn II 0:50 Fe II 0:50 PO 4 and a mixed composition Li 0.70 Mn II 0:50 Fe II 0:20 Fe III 0:30 PO 4 up to x = 0.50.…”

“…, and this further confirms that the Fe 3+ is very sensitive to the oxidation state of Mn since an increase of the amount of Mn 3+ around the Fe 3+ site lead to a significant increase of the quadrupole splitting31 . Similar spectra have been reported for natural purpurite (Fe,Mn)PO 4 31 .…”

“…5a It is worth noting that such phases (called ferrisicklerites Li x,1 (Fe,Mn)PO 4 ) have been reported by mineralogists and attributed to natural oxidation of triphylite Li(Fe,Mn)PO 4 . [32][33][34] From the study of 45 ferrisicklerite minerals, Fanton et al have concluded on the absence of any structural order of the Mn and Fe cations in this family of materials. 32 From these observations we conclude a biphasic mechanism with the coexistence of LiMn II 0:50 Fe II 0:50 PO 4 and Li 0.70 Mn II 0:50 Fe II;III 0:50 PO 4 for the charge and discharge in the range 0.70 ¡ x , 0.95.…”

Pair distribution function analysis and Mössbauer study of defects in microwave-hydrothermal LiFePO4

“…A survey at the published literature on the subject reveals that spectra similar to the ones reported below were fitted by introducing broad Lorentzian lines, site distributions and/or by considering dynamical effects 15,[33][34][35][36][37][38][39][40][41][42][43] which cause the Mo ¨ssbauer line shape to deviate from the standard Lorentzian trend. Anyway, we note that in ref.…”