Crystal structure and the
57Fe Mössbauer spectrum of synthetic (Ca
1.53Na
0.47)(Mg
0.52Fe
3+0.49)Si
1.99O
7-melilite have been investigated to confirm the location of Fe
3+ at the
T1 site, and to evaluate the effect of an incommensurate structure on 57Fe Mössbauer hyperfine parameters. A conventional Rietveld refinement with occupancies of Ca(
W), Na(
W), Mg(
T1), Fe
3+(
T1) and Si(
T2) fixed to 0.765, 0.235, 0.515, 0.485 and 2.00, respectively, converged well with an
Rwp (
R-weighted pattern) of 13.14% and a goodness-of-fit of 1.337, indicating exclusive Fe
3+ distribution at the
T1 site. However, the Mössbauer spectrum consists of two doublets with an isomer shift of 0.19 mm/s and quadrupole splitting of 0.75 and 1.04 mm/s, which can be attributed to Fe
3+ at the
T1 site. There are two sorts of
T1 site with distinguishable distortion in the synthetic Na-Fe
3+-melilite, which might be attributed to the existence of an incommensurate phase at room temperature.
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