Developments in Ceramic Materials Research

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José M. Rojo, José L. Mesa and Teófilo Rojo
Figure 2. Energy-level diagram for the d 3 configuration in an octahedral field.
4.4. Mössbauer Spectroscopy
The Mössbauer spectra of Fe(PO3)3 metaphosphate were collected at temperatures of 300,
77 and 4.2 K (Figure 3).
At room temperature the spectrum shows one doublet paramagnetic quadrupolar that is
characteristic of high spin, d 5 , Fe(III) in octahedral geometry [30]. The spectrum was fitted
using the NORMOS program [31] employing three doublets. One of them for every iron(III)
crystallographic independent, with equal isomer shift and quadrupolar splitting. The values of
the isomer shift and quadrupolar splitting are in good agreement with those found in others
iron(III) phophates, NaFe(P2O7) and Na3Fe2(PO4)3 [32,33]. The spectrum collected at 77 K
also shows a doublet quadrupolar that was also fitted with three doublets characteristic of the
three iron(III) crystallographic independents. In comparison with the spectrum at room
temperature this later exhibits larger values of the isomer shift and line-width a medium high.
Finally, the spectrum at 4 K shows a sextet characteristic of the existence of an ordering of
this phase at low temperature. The value of the isomer shift is 0.57 mm/s, being in the range
of these ones observed for iron(III) compounds [34].The spectrum at 4 K was fitted with three
magnetic sextuplets, being the line-width of 0.50 mm/s. This result is in good agreement with
the structural data. The values at 4 K of the electronic perturbation are negatives. This result
indicates the existence in the neighbouring of the Fe(III) nuclei of electric charge with slightly
asymmetrical distribution. The magnetic interaction in this phase takes place through Fe(III)
cations, which generate in the ordered state, 4K, approximately, hyperfine fields of =
48.6, 50.90 and 52.3 T, under every iron(III) nuclei, respectively.