A dravite from Yemen of near end-member composition was treated in air and hydrogen atmospheres at 600–900 °C to reveal changes in Mg and Al order over the octahedrally coordinated Y and Z sites, and to explore related changes in the characteristic vibrational bands in the principal (OH)-stretching frequency. Relevant infor- mation was obtained using electron microprobe analysis (EMPA), structural refinement (SREF) and polarized infra- red (IR) single-crystal spectroscopy. Overall, the EMPA, SREF and IR data show that only minor changes occur during thermal treatment up to at least 800 °C, including variations in structural parameters, Mg–Al order–disor- der and (OH)-stretching bands, indicating limited hydro- gen loss. Untreated and treated dravite samples have very similar long-range and short-range atomic structures, which may be related to the occurrence of stable Al–Mg extended clusters around the O1 (=W) and O3 (=V) sites: W(F)–Y(MgMgMg)–V(OH)3–Z[AlAlAlAlAl(Al,Mg)]; W(OH)–Y(MgMgAl)–V(OH)3–Z[AlAlAlAlAl(Al,Mg)]; W(O2–)–Y(AlAlAl)–V(OH)3–Z[AlAlAlAlAl(Al,Mg)]. These extended clusters remain stable to temperatures close t
Thermal stability of extended clusters in dravite. A combined EMP, SREF and FTIR study / Bosi, Ferdinando; Skogby, Henrik; Balić Žunić, Tonči. - In: PHYSICS AND CHEMISTRY OF MINERALS. - ISSN 0342-1791. - STAMPA. - 43:6(2016), pp. 395-407. [10.1007/s00269-016-0804-y]
Thermal stability of extended clusters in dravite. A combined EMP, SREF and FTIR study
BOSI, Ferdinando
;
2016
Abstract
A dravite from Yemen of near end-member composition was treated in air and hydrogen atmospheres at 600–900 °C to reveal changes in Mg and Al order over the octahedrally coordinated Y and Z sites, and to explore related changes in the characteristic vibrational bands in the principal (OH)-stretching frequency. Relevant infor- mation was obtained using electron microprobe analysis (EMPA), structural refinement (SREF) and polarized infra- red (IR) single-crystal spectroscopy. Overall, the EMPA, SREF and IR data show that only minor changes occur during thermal treatment up to at least 800 °C, including variations in structural parameters, Mg–Al order–disor- der and (OH)-stretching bands, indicating limited hydro- gen loss. Untreated and treated dravite samples have very similar long-range and short-range atomic structures, which may be related to the occurrence of stable Al–Mg extended clusters around the O1 (=W) and O3 (=V) sites: W(F)–Y(MgMgMg)–V(OH)3–Z[AlAlAlAlAl(Al,Mg)]; W(OH)–Y(MgMgAl)–V(OH)3–Z[AlAlAlAlAl(Al,Mg)]; W(O2–)–Y(AlAlAl)–V(OH)3–Z[AlAlAlAlAl(Al,Mg)]. These extended clusters remain stable to temperatures close tFile | Dimensione | Formato | |
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