CRYSTALLOCHEMICAL PROPERTIES OF NH4(FE1-XMNX)PO4-CENTER-DOT-H2O

The industrial and agricultural uses of orthorhombic metal ammonium phosphates of formula NH4-MPO(4).H2O [M = Fe(II), Mn(II), Mg, Co(II), or Cu(II)] justify their detailed study. In this work, the X-ray diffraction patterns and the stability of NH4(Fe1-xMnx)PO4.H2O to oxidation were investigated. In the study of six members of this series (x = 0, 0.2, 0.4, 0.6, 0.8, and 1.0) stability to heating and oxidation increased with increasing Mn content. The unit-cell parameters a, b, and c of 52 products with different values of x and degrees of oxidation could be predicted by x and the Fe(II)/(Fe + Mn) ratio. Accordingly, there was good agreement between measured crystallographic d-spacings and spacings calculated from predicted a, b, and c values. For the Fe end member, the calculated crystalline parameters were a = 5.6659, b = 8.7885,and c = 4.8325.