SYNTHESIS AND STUDY BY MOSSBAUER-SPECTROSCOPY OF LIPSCOMBITE (FE23+FE2+(PO4)(2)(OH)(2)) PARTIALLY SUBSTITUTED BY MANGANESE, COBALT, AND CHROMIUM CATIONS
D. Rouzies et al., SYNTHESIS AND STUDY BY MOSSBAUER-SPECTROSCOPY OF LIPSCOMBITE (FE23+FE2+(PO4)(2)(OH)(2)) PARTIALLY SUBSTITUTED BY MANGANESE, COBALT, AND CHROMIUM CATIONS, Journal of physical chemistry, 99(33), 1995, pp. 12576-12580
Recent investigations claimed the use of lipscombite, Fe23+Fe2+(PO4)(2
)(OH)2, as a catalyst for the oxidative dehydrogenation of isobutyric
acid. In the present study, the synthesis and characterization by Moss
bauer spectroscopy of Mn-, Co-, and Cr-substituted lipscombites are de
scribed. It is found that lipscombite substituted by 10%, 20%, and 30%
of cobalt and manganese could be prepared while the substitution by c
hromium did not exced 20%. Mossbauer spectroscopy along with other phy
sicochemical characterization techniques showed that Fe-2-x(3+),M(x)(2
+)Fe2+(PO4)(2-x)(HPO4)(x)(OH)(2) (M = Mn or Co) type solid solutions
were obtained instead of Fe-2(3+)Fe(1-x)(2+)M(x)(2+)(PO4)(2)(OH)(2)
solid solutions which exist for natural compounds. Chromium-substitute
d compounds belonged to a Fe2-x3+Crx3+Fe2+(PO4)(2)(OH)(2) limited so
lid solution (x < 0.3). Mn2+, Co2+ and Cr3+ were found to preferential
ly occupy in the lipscombite structure two ferric cations sites Fe(3)b
and Fe(3)a, which differ by their cationic surrounding.