Structural studies of zinc ammonium sulphate and magnesium ammonium sulphate mixed crystals – By X-ray diffraction

The cubic mineral langbeinite K2Mg2 (SO4)3 and its isomorphs A+1B+2 (SO4)3 where A+1 = K, Rb, Cs, Te, NH4+ and B+2 = Mg, Ca, Zn, Mn, Fe, Co and Ni are known for their ferro electric properties. The zinc ammonium sulphate magnesium ammonium sulphate mixed crystals of varying proportions are grown by solution technique and the characterization studies are carried out. By knowing the cell parameters from the available ASTM index for the pure crystals and by adopting the Reitvield refinement procedure from their atomic positions, the h, k, l values of the pure crystals are calculated. From the calculated h, k, l values, the cell parametrs of the pure crystals and the X-ray powder diffraction pattern of the mixed crystals, the cell ‘n’ programme is generated and cell parameters of the mixed crystals are calculated. Some of the calculated values are checked by single crystal analysis. The X-ray Laue pattern is taken and this confirms the single crystallinity and P21 /a monoclinic nature. The gradation in the cell parameters is analysed and discussed.