Mössbauer Effect and X-ray Studies of the Phase Transitions in K 2 Fe(SO 4 ) 2 ·nH 2 O(n=2,4,6)

A detailed study of Mössbauer spectra for K 2 Fe(SO 4 ) 2 ·nH 2 O(n=2,4,6) has been performed. Isomer shift and quadrupole splitting of 57 Fe were measured as functions of temperature between 90 K and 370 K. Single crystals of dipotassium iron sulfate, K 2 Fe(SO 4 ) 2 ·nH 2 O were grown by slow evaporation of aqueous solutions of K 2 SO 4 and FeSO 4 in equimolar ratio. Since it was necessary to keep the solution above 360 K to obtain dihydrate crystals, K 2 Fe(SO 4 ) 2 ·2H 2 O was grown at 369 K. The crystal is known to undergo a phase transition which is associated with the water molecular orientation. The Mössbauer study was also performed on the crystals K 2 Fe(SO 4 ) 2 ·4H 2 O and K 2 Fe(SO 4 ) 2 ·6H 2 O for the search of the possible phase transitions similar to that of K 2 Fe(SO 4 ) 2 ·2H 2 O. The part of the X-ray structure analysis for these crystals is also given.