Extended X-ray absorption fine structure study of potassium and caesium phyllomanganates

Abstract

Mn, K and Cs EXAFS spectra have been measured for four phyllomanganates A_xMnO_2±δ·yH₂O with A = K and Cs and variable values of x and δ. For manganese, the distances and the number of neighbours fit very well the typical Mn⁴⁺ coordination with layers of corner-sharing Mn—O octahedra. The potassium and caesium environments are very similar to those found in the known layered vanadates AV₃O₈(A = K, Cs). The height of the interlayer space is described well by a simple structural model and is directly related to the size of A for dehydrated samples. These results confirm the ability of the phyllomanganate structure to accommodate interlayer cations as large as K⁺ and Cs⁺.