Mn-olivine

Fig. 18 The electrical conductivity of LiMP04 (M=Fe, Ni, Co, Mn) olivine materials. Numbers indicate the activation energy in eV. The low conductivity is related to the small free volume and separation of MOg octahedra by oxygen atoms of the (P04) anions...

The third family of 5-V cathode materials is based on poly-anionic frameworks with the olivine and olivine-related structures. Recently, a short review of this class of materials, as cathodes for advanced lithium-ion batteries, has been puhhshed [14]. Since the discovery of the electrochemical activity of LiA/P04 (M = Fe, Mn) olivines with and redox potentials 3.5 and 4.1 V versus LF/Li,... 

Different minerals contain different metal cations to balance the -4 charge on the orthosilicate ion. Examples Include calcium silicate (Ca2 Si04), an important ingredient in cement, and zircon (ZrSi04), which is often sold as artificial diamond. One of the most prevalent minerals in the Earth s mantle is olivine, Af2(Si04), in which M is one or two of the abundant metal cations, Fe -, Mg -, and Mn +. 

Similarly to Mn(IV)- and Fe(III)-oxides, some primary minerals were shown to promote polymerization of hydroquinone (19). Olivines, pyroxenes, and amphiboles accelerated the polymerization reaction to a greater extent than micas and feldspars. Microcline and quartz were ineffective- The effect was greatest for tephroite, a manganese-bearing silicate with the ideal chemical formula M SiO. Fayalite, the corresponding Fe(II) analog (Fe2Si0 ), was effective, but to a lesser extent. 

Despite quite some progress reported in improving the performance and lifetime of anode materials, a great deal of research needs to be dedicated to the improvement of the cathode in Li-ion batteries. This task was addressed by hydrothermal carbon coating techniques. Thus, Olivine LiMP04 (Me = Mn, Fe, and Co) cathodes with a thin carbon coating have been prepared by a rapid, one-pot, microwave-assisted hy-... 

Recently, LiFeP04, which adopts the olivine structure, has been widely studied as a possible cheap cathode material.Although the specific capacities of this material and the related NASICON structures are relatively low (typically 100 mAhg ), these compounds are cheap and open up new avenues for research. Li MAS NMR studies of a series of olivines LiMP04 with M = Mn, Fe, Ni, and Co were carried out by Tucker et A single resonance with large... 

Figure 4AO Distribution profiles of Mn and Mg along axis c in the olivine mixture (Mn Mgi j2Si04 after couple annealing at 1200 °C for 277 hours. From Morioka and Nagasawa (1991). Reprinted with permission of Springer-Verlag, New York.

Mn Mgi )2Si04 olivine mixture obtained by Morioka (1981). The concentration profiles are symmetric, indicating that the diffusivities are independent of the concentration of the diffusing ion. On the contrary, possible asymmetry in the diffusion profiles indicate that concentration depends significantly on the diffusing cations. In this case, the interdiffusion coefficient can be obtained by the Boltzmann-Matano equation ... 

Figure 10 J Compositional effects of melt on olivine/liquid mass distribution of Mn +. Reprinted from E. B. Watson, Geochimica et Cosmochimica Acta, 41, 1363-1374, copyright 1977, with kind permission from Elsevier Science Ltd., The Boulevard, Langford Lane, Kidlington 0X5 1GB, UK.

Figure 10,20 Major element concentrations in effusive products of Boina series plotted as functions of degree of fractional crystallization, based on equation 10.132. I = first discontinuity (transition from olivine-dominated to plagioclase-dominated fractionation) II = second discontinuity (appearance of Fe-Ti oxides) III = third discontinuity (field of Si02 oversaturated trachytes apatite and Mn-oxides precipitate) IV = beginning of peralkalinity field. From Barberi et al. (1975), Journal of Petrology, 16, 22-56. Reproduced with modifications by permission of Oxford University Press.

Annersten H., Adetnuji I, and Filippidis A. (1984). Cation ordering in Fe-Mn silicate olivines. Amer. Mineral, 69 1110-1115. 

Finnerty T. A. (1977). Exchange of Mn, Ca, Mg and A1 between synthetic garnet, orthopyroxene, clinopyroxene and olivine. Carnegie Inst. Wash. Yb., 68 290-292. 

Wood B. J., Hackler R. T. and Dobson D. P. (1994). Experimental determination of Mn-Mg mixing properties in garnet, olivine and oxide. Contrib. Mineral Petrol, 115 438-448. 

The crystal radius thus has local validity in reference to a given crystal structure. This fact gives rise to a certain amount of confusion in current nomenclature, and what it is commonly referred to as crystal radius in the various tabulations is in fact a mean value, independent of the type of structure (see section 1.11.1). The crystal radius in the sense of Tosi (1964) is commonly defined as effective distribution radius (EDR). The example given in figure 1.7B shows radial electron density distribution curves for Mg, Ni, Co, Fe, and Mn on the M1 site in olivine (orthorhombic orthosilicate) and the corresponding EDR radii located by Fujino et al. (1981) on the electron density minima. 

Epidote-clinozoisite Ca2(Al, Fe )3(Si04)3(0H) Piedmontite Ca2(Al,Mn+ Fe+= )3(Si04)3(0H) Zoisite Ca2Al3(Si04)3(0H) dimorph clinozoisite Humite (morphotrophic series with olivine)... 

Figure 3-5 MnO partition between and diffusion in two minerals, olivine and garnet. Diffusional anisotropy of olivine is ignored. Initially, MnO in both phases were 0.2 wt%. As the two minerals come into contact, there will be diffusion to try to reach the equilibrium state. The partition coefficient (Mn)oiiv/(Mn)gt is assumed to be 0.59. The diffusivity in olivine is assumed to be 10 times that in garnet, resulting in a wider diffusion profile with a smaller slope in olivine.

Mn 1190 Mn2Si04 in olivine mod. volatile Dy 1598 dissolved in CaTiOj refr. lithophile... 

Orthosilicates or neso-silicates Isolated [Si04] tetrahedra Olivine, (Mg, Fe, Mn)(Si04) Zircon, Zr(Si04)... 

This oxidation of iron is of importance for carbonation of magnesium oxide-based silicates for CCS, using for example olivine which a mixture of Mg2Si04 (forsterite) and Fe2Si04 (fayalite). In other similar situations, the oxidation of Fe or Mn ions can limit the reaction with (dissolved) C02. 

The technique of channeling-enhanced X-ray emission (CHEXE) has enabled cation site occupancies to be determined in various minerals, including transition metal ions in spinels and ferromagnesian silicates (Taftp, 1982 Taftp and Spence, 1982 Smyth and Taftp, 1982 McCormick etal., 1987). The method, which is based on relative intensities of X-ray peaks measured on crystals with diameters as small as 50 nm under the electron microscope, is particularly useful for determining site occupancies of minor elements with concentrations as low as 0.05 atom per cent in a structure. The most important criterion for the determination of element distribution in a mineral by this technique is that the cation sites should lie on alternating crystallographic planes. In order to make quantitative site population estimates, additional information is required, particularly the occupancy of at least one element in one of the sites or in another site that lines up with one of the sites of interest (McCormick et al., 1987). For example, cation site occupancies by CHEXE measurements have been determined from X-ray peak intensity ratios of Si to Ni, Mn, Cr and Fe in forsterite, as well as thermal disordering of these cations in heated olivines (Smyth and Taftp, 1982). 

The Ni2+, Cr3+ and low-spin Co3+ ions do not acquire additional stabilization in distorted octahedral sites. They are expected to favour smaller sites that more closely approximate octahedral symmetry than other available sites in the crystal structures. As noted in 6.8.2, the high octahedral CFSE s acquired by these three cations in small octahedral sites in silicate and oxide structures accounts for the observed relative enrichments of Ni2+ in the olivine Ml and orthopyroxene Ml sites, the sole occupancy by Cr3+ of pyroxene Ml sites, and the occurrence and stability of low-spin Co3+ in Mn(IV) oxides. 

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