Crystal growth and thermal properties of the Tutton salt Cs sub(2)Fe(SO sub(4)) sub(2).6H sub(2)O single crystal

Thermal properties and phase transitions of the Tutton salt Cs sub(2)Fe(SO sub(4)) sub(2).6H sub(2)O were investigated using thermogravimetric analysis, differential scanning calorimetry, and nuclear magnetic resonance (NMR). The first occurrence of mass loss is at approximately 321 K (=T sub(d)) and is interpreted as being the onset of partial thermal decomposition. Phase transitions were observed at 356 K (=T sub(C1)) and 450 K (=T sub(C2)). The temperature dependence of the NMR spectrum and spin-lattice relaxation time T sub(1) for the super(133)Cs nuclei abruptly changes near T sub(C1). These changes are associated with changes in the geometry of the water and five SO sub(4) oxygens around the Cs ions.