ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
The prediction made in J. Appl. Phys. 65, 3987 (1989) that the ferroelectric–ferroelastic phase transition at Tc =490 K in K3Fe5F15 will be accompanied by a change from order to disorder among the Fe2+/Fe3+ ions has been confirmed by Mössbauer spectroscopy. The thermal dependence of both the Fe3+ quadrupolar splitting and the Fe3+ isomer shift exhibits a smooth decrease with increasing temperature to Tc, each with a sharp and reproducible change in slope above Tc. The average Fe2+ quadrupolar splitting (QS) similarly undergoes a major decrease with increasing temperature, with a clear change in slope above Tc. Furthermore, the thermal dependence of the Fe2+ QS distribution shows that the Fe2+/Fe3+ order required crystallographically below Tc is not conserved at higher temperatures. The proportion of Fe2+ present below Tc is close to the stoichiometric 60% value; the proportion decreases above Tc rapidly with temperature and becomes less than 50% by 543 K, consistent with increasing delocalization of an Fe2+ electron.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.345219
