1B, calcined at different rates (5, 10 and 15 AdegC / min) up to 800 AdegC, showed the production of Orthorhombic Mn2O3 (bixbyite
) with hkl value (222).
The Raman spectra of the NAR formed on the 18Mn mainly presented bands at 554, 390, 621, 598, and 500 [cm.sup.-1], where the first two bands correspond to goethite and the last three bands possibly correspond to Mn-rich bixbyite
X-ray diffraction of the as-deposited and annealed films could be indexed assuming the cubic bixbyite
structure of the pure ITO .
occurs in small proportions in creamy- grey color and is isotropic with no internal reflection.
The standards selected for Mn were birnessite [([(Na, Ca).sub.0.5]([Mn.sup.4+], [Mn.sup.3+]).sub.2] [O.sub.4].1.5[H.sub.2]O), hureaulite ([(Mn, Fe).sub.5][H.sub.2][(P[O.sub.4]).sub.4].4[H.sub.2]O), manganocalcite (Mn-CaC[O.sub.3]), Mn-carbonate (MnC[O.sub.3]), Mn-sulfate (MnS[O.sub.4]), bixbyite
([Mn.sub.2][O.sub.3]), pyrolusite (Mn[O.sub.2]), and switzerite ([(Mn, Fe).sub.3][(P[O.sub.4]).sub.2].7[H.sub.2]O).
Generally, the equilibria of Mn[O.sub.2] (pyrolusite), [Mn.sub.2][O.sub.3] (bixbyite
), [Mn.sub.3][O.sub.4] (hausmannite), MnC[O.sub.3] (rhodochrosite), and Mn[(OH).sub.2] (pyrochroite) with [Mn.sup.2+] are the dominant Mn systems in soil (Gotoh and Patrick 1972).
These prismatic, well terminated crystals, some associated with sharp black cubic bixbyite
crystals, are hardly "new," having been first discovered in 1859 (according to a 1979 article by Lanny Ream: see vol.
Inclusions found within the topaz include quartz, bixbyite
, and psuedobrookite.
[MnO.sub.2] was found to lose oxygen at about 600 [degrees]C and 950 [degrees]C to bixbyite
([MnO.sub.2][O.sub.3]) and [Mn.sub.3][O.sub.4] (hausemannite).
Calcination at 500[degrees]C leads to the formation of bixbyite
[Mn.sub.2][O.sub.3] (JCPDS number 00-002-0909) (Figure 3).
Addition of KMn[O.sub.4] was characterised by large removals of calcium and manganese as birnessite, pyrolusite and nsutite (Mn[O.sub.2]), hausmannite ([Mn.sub.3][O.sub.4]), bixbyite
([Mn.sub.2][O.sub.3]), manganite (MnOOH), and fluorite (Ca[F.sub.2]).
The mineral bixbyite
, which he discovered there, was named in his honor by Penfield and Foote in 1897.