Fe⁵⁷ Mössbauer spectroscopic studies of iron silicates with the mordenite topology

Fe⁵⁷ Mössbauer spectroscopic studies on an as-synthesized sample of iron silicates with the mordenite topology/mordenite (Fe)/ferrimordenite, which was substantially free from Al ( SiO₂ Al₂O₃ > 1000), have been carried out at room temperature (RT). 4.2 K, and in the presence of an externally applied magnetic field 4.13 T). The derived hyperfine interaction parameters at RT (IS = 0.24 ± 0.02 mm/s, Δ EQ = 0.59 ± 0.02 mm/s, and at 4.2 K, IS = 0.34 ± 0.02 mm/s, Δ EQ = 0.61 ± 0.02 mm/s), clearly indicated the presence of most of the iron ions at high-spin Fe³⁺ (⁶S _{5 2}) in nearly symmetric tetrahedral sites. Low-temperature/high-magnetic field spectra revealed the average internal field of 460 ± 10 KOe. These results confirm the uniform dispersion of Fe³⁺ ions in the tetrahedral framework of ferrimordenite.