THERMAL DEPENDENCE OF INTRACRYSTALLINE Fe2 -Ca2 EXCHANGE IN METASILICATE, FERROBUSTAMITE Ca, FeSiO3Reportar como inadecuado




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Abstract : Intracrystalline Fe2+-Ca2+ exchange in ferrobustamite space group AMATH ; unite cell parameter a = 7.862 Å, b = 7.253 Å, c = 13.967 Å, α = 89°44-, β = 95°28-, γ = 103°29- ; chemical composition Ca0.816Fe0.l52Mn0.032SiO3 is confirmed by the measurements of absorption intensities of the Mössbauer spectra. Rate constants of the exchange reaction, FeM3 + CaM1,2 = FeM1,2 + CaM3 are obtained by the variation of site occupancies of Fe atoms in the M1, M2 and M3 sites of samples heated at 1000 °C, 800 °C, 700 °C and 600 °C in different heating periods. Activation energies in both disordering and ordering processes in the exchange reaction are determined to be 27.61 kcal and 18.45 kcal, respectively. The standard free energy difference ΔG° in the cation exchange is approximately constant, as calculated by the intracrystalline distribution function.





Autor: T. Yamanaka R. Sadanaga

Fuente: https://hal.archives-ouvertes.fr/



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