Investigation of the KNd(SO4)2·H2O–SrSO4·0.5H2O System

The cocrystallization of potassium, neodymium, and strontium sulfates from aqueous solutions has been studied using X-ray powder diffraction, thermogravimetry, energy-dispersive X-ray spectral analysis, and electron microscopy. Extensive solid solutions based on trigonal KNd(SO4)2⋅H2O have been found to exist in the concentration range 100–20 mol % of the KNd(SO4)2⋅H2O–SrSO4⋅0.5H2O system. The unit cell parameters of the solid solutions have been determined. Two phases have been discovered: trigonal KNd(SO4)2⋅H2O (space group P3121) and monoclinic KNd(SO4)2⋅H2O (space group P21/c1). The heterovalent substitution scheme 2Sr2+ → K+ + Nd3+ stabilizes the structure of solid solutions based on the isostructural KNd(SO4)2⋅H2O and SrSO4⋅0.5H2O trigonal phases.