Characterization of lepidolites by Raman and infrared spectrometries; I, Relationships between OH-stretching wavenumbers and composition

摘要: Four partial solid-solutions that affect lepidolite compositions have been investigated by Raman scattering and infrared absorption spectrometries, in the wavenumber range of OH-stretching vibration (y - OH); every case, both methods gave same values, within experimental errors. The synthesized belong to solid solutions between phlogopite each end members: taeniolite, trilithionite polylithionite (all purely trioctahedral) j oin tetrasilicic magnesium mica which exhibits a dioctahedral character. On first three joins, changes evolution ofspectra reflect compositional especially increase lithium contenU all bands observed trioctahedral type. Three subtypes are characterized bulk number charges adjacent cations: "5-charge bands", due OH groups bonded Mg2Li or Li2Al (range 3755-3740 cm-r); "6-charge bands', Mg3 AlMgLi (range3740-37 15 cm-1) "7-charge Mg2Al Al2Li (z < 3700 cm-l). basis these observations, new nomenclature is proposed, relevant any mica. join an additional dioctahedral-type band at 3595 cm-l 2Mg octahedral vacancy. This constant along join, indicating exclusion Li+ from proximity ofthese hydroxyl groups. For triocrahedral-type bands, systematic shift toward low wavenumbers, as aluminum content (Alro) increases phenomenon, already known solid-solutions, related change composition explained OH...O interactions weak hydrogen bonding proton apical oxygen atoms surrounding tetrahedra. These variations can be expressed tlree equations, valid for light elements: (l) z = -9.33Alot + 3754 (S-charge bands); (2) / : -l6.95Altot 3741 (6charge bands), (3) v -29.66.A{.t 3719 (7