Mössbauer Investigation of Ferroelectric Boracites

The Mössbauer spectra of 57Fe in the iron‐boracites Fe3B7O13X with X = Cl, Br, or I, and of 57Fe as an impurity in Ni3B7O13X have been measured at temperatures between 80 and 1100 °K. The results give qualitative information on the vibration amplitude in the different phases, on the crystal field splitting of the Fe2+ ion in the cubic phase, and on the character of the binding of the Fe2+ ion, and have led to the discovery of a trigonal phase in the Fe boracites.