Εξειδίκευση τύπου :	Άρθρο σε επιστημονικό περιοδικό
Τίτλος:	Unusually high oxidation states of manganese in high optical basicity silicate glasses
Δημιουργός/Συγγραφέας:	Ashjari, Amir Topper, Brian Hess, Lars H. Greiner, Lucas Tolliver, Jared Cormack, Fiona [EL] Παλλές, Δημήτρης[EN] Palles, Dimitris [EL] Καμίτσος, Ευστράτιος Ι.[EN] Kamitsos, Efstratios I. Brik, Mikhail G. Möncke, Doris
Ημερομηνία:	2024
Γλώσσα:	Αγγλικά
ISSN:	25901478
DOI:	10.1016/j.omx.2024.100371
Περίληψη:	Unusually high oxidation states of manganese were stabilized within a cesium-barium silicate (CBS) glass system of extremely high optical basicity. The highest basicity was obtained for the metasilicate glass 40Cs2O–10BaO–50SiO2 (mol%) with an optical basicity of = 0.81. The presence of Mn5+ (d2) as well as Mn6+ (d1) is confirmed by UV–Vis, photoluminescence, and Raman spectroscopy. The UV–Vis spectrum is dominated by the Mn3+ (d4) absorption at 526 nm for low-basicity glasses, which is replaced by a peak at 679 nm (Mn5+) and, finally, a band at 603 nm (Mn6+) in the glass with the highest basicity ( = 0.81). In this glass, the Mn5+/Mn6+ ratio varies with the melting conditions. Photoluminescence (PL) spectroscopy under 633 nm excitation confirms the presence of Mn5+, showing the narrow, forbidden 1E 3A2 transition located at 1191 nm with vibrational sidebands at 1245 nm and 1290 nm. The measured static fluorescence intensity due to Mn5+ grows exponentially with increasing optical basicity. The near infrared fluorescence decay was bi-exponential, with time constants of 14 and 51 μs. The absence of Mn4+ in CBS glasses was confirmed by PL and electron paramagnetic resonance (EPR) spectroscopy. Despite initial doping as MnO2, metastable Mn4+ disproportionates into lower and higher valent manganese species, followed by reduction or oxidation of manganese to a stable species as ruled by the basicity of the glass and oxygen availability during melting. A structural study of the glasses by Raman spectroscopy revealed a resonance enhancement effect for the symmetric stretching mode of MnO4-tetrahedra at ∼800 cm−1 with overtones observed at higher frequencies.
Τίτλος πηγής δημοσίευσης:	Optical Materials: X
Τόμος/Κεφάλαιο:	24
Θεματική Κατηγορία:	[EL] Φασματοσκοπία[EN] Spectroscopy [EL] Ανόργανη χημεία[EN] Inorganic chemistry
Λέξεις-Κλειδιά:	cesium-barium metasilicate hgh optical basicity resonance Raman enhancement Mn5+ Mn6+ redox equilibria optical spectroscopy
EU Grant identifier:	DMR-1626164
Κάτοχος πνευματικών δικαιωμάτων:	© 2024 The Authors. Published by Elsevier B.V.
Όροι και προϋποθέσεις δικαιωμάτων:	This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/bync-nd/4.0/).
Ηλεκτρονική διεύθυνση στον εκδότη (link):	https://doi.org/10.1016/j.omx.2024.100371
Εμφανίζεται στις συλλογές:	Ινστιτούτο Θεωρητικής και Φυσικής Χημείας (ΙΘΦΧ) - Επιστημονικό έργο