Mössbauer Spectrometric Study of Hureaulite

Abstract

The various compositions of hureaulite, (Mn_1-x, Fe_x)₅H₂(PO₄)₄4 H₂O, were synthesized by adding 1 mol/l solutions of manganese sulfate and iron(II) sulfate to a 0.3 moll/ solution of disodium hydrogen phosphate (pH 5) at higher temperature than 95°C in the stream of nitrogen to prevent the samples from the oxidation of iron(II). The chemical states of substituted iron were investigated by means Of the MOssbauer spectrometry.
It was found that the iron( III) ions fill the three m anganese sites [M( 1 ), M( 2 ) and M( 3)]of octahedra of hureaulite structural unit to the degree up to 100%, and that the distribution coefficient of iron (II) ion to the M( 2 ) site of hureaulite structure increases with the increase of iron contents. The relationship between the ratio of peak intensity of the Mössbauer spectra, y=IM(2)/(IM(1)+IM(2) + IM(3)), and the fraction of iron and manganese in hureaulite, x =Fe/(Fe+Mn), is found to be expressed approximately by the equation, x=4.7 y-1.2, sugges ting a possibility of estimating the iron contents in iron(II) substituted hureaulite. Finally, the distribution diagram of iron and manganese in hureaulite was shown with regard to each site of octahedra in Fig.5.