127I-NQR, 119 Sn Mössbauer Effect, and Electrical Conductivity of MSnI3 (M = K, NH4 , Rb, Cs, and CH3NH3 )

Abstract

Abstract In a series of MSnI3 compounds (M = K, NH4 , Rb, Cs, CH3NH3) two types of coordination around the central Sn(II) were found by 127I-NQR and powder X-ray diffraction techniques. They are square pyramidal (for M = NH4 , Rb) and octahedral (for M = CH3NH3). CsSnI3 , on the other hand, showed a drastic structural change of the anion at 425 K from a square pyramid to a regular octahedron. Associated with this phase transition, the electrical conductivity increased from 4 x 10-3 S cm-1 to about 102 S cm-1 . This metallic modification was characterized by 127I-NQR and 119Sn Mössbauer spectroscopy.