Cation distribution in natural Zn-spinels: franklinite
Lucchesi, Sergio; Russo, Umberto; Giusta, Antonio Della
European Journal of Mineralogy Volume 11 Number 3 (1999), p. 501 - 512
published: May 25, 1999
manuscript accepted: Dec 17, 1998
manuscript received: Jan 20, 1998
ArtNo. ESP147051103009, Price: 29.00 €
Abstract The intracrystalline cation distribution of nine franklinite samples from Franklin and Sterling (New Jersey, USA) was determined by means of single-crystal X-ray structural refinement supported, for some samples, by Mossbauer spectroscopy. The principal substitutions observed were Al for Fe3+ on the octahedral site and Mn2+ for Zn on the tetrahedral site. Small amounts of Mn3+ were required by stoichiometry in all samples. Consequently Fe2+ was totally absent, as confirmed by room-temperature Mossbauer spectra. The latter experiments also suggested limited inversion, that is, Fe3+ in the tetrahedral site, essentially balanced by Mn2++Zn in the octahedral site. To obtain consistent cation distributions in these Zn-ferrites, it was necessary to adopt a Zn-O distance of 1.999 Å, a value very different from that previously used in Zn-aluminates (1.960 Å), confirming observations by other authors on synthetic samples.