Espectroscopia Mossbauer em columbita/tantalita

Abstract

Mossbauer Spectroscopy has been applied to.study the iron sites of natural samples of the solid solution Columbite/Tantalite, (Fe, Mn) (Nb, Ta) 206. In the various samples three sites of Fe +2 have been observed. The site A ( ô = 1,14 mm/s and A = 1,65 mm/s) has been identified as Columbite (FeNb2o6) and the site C ( o = 1, 11 mm/s and A = 3,03 mm/s) as Tantalite (FeTa2o6). Cassiterite or Green Tourmaline are proposed for the third si te C ô = 1, 10 mm/s and A = 3, O 3 mm/s). A study of the temperature dependence of the isomer shift and quadrupole splitting CllO and 180K) has been made. Some measurements at liquid heliun ternperatUJ'.'e have also been made. It has not been observed in any sample the simultaneous ocurrence of Columbite and Tantalite. A density diagrarn for this solid solution s.ugests that in some sarnples the Ta is preferably bound to Mn.