Εξειδίκευση τύπου :	Άρθρο σε επιστημονικό περιοδικό
Τίτλος:	Short-range structure, the role of bismuth and property-structure correlations in bismuth borate glasses
Δημιουργός/Συγγραφέας:	[EL] Βαρσάμης, Χρήστος-Πλάτων Ε.[EN] Varsamis, Christos-Platon E. Makris, N. Valvi, C. [EL] Καμίτσος, Ευστράτιος Ι.[EN] Kamitsos, Efstratios I.
Ημερομηνία:	2021-04-28
Γλώσσα:	Αγγλικά
DOI:	10.1039/d1cp00301a
Άλλο:	33870996
Περίληψη:	Bismuth-containing borate glasses, xBi2O3-(1 - x)B2O3, were synthesized in the broad composition range 0.20 ≤ x ≤ 0.80 by melting in Pt crucibles and splat-quenching between two metal blocks. Infrared reflectance spectra, measured in the range 30-5000 cm-1, were transformed into absorption coefficient spectra and then deconvoluted into component bands to probe the glass structure as a function of composition. Integrated intensities of bands above 800 cm-1 were used in combination with mass and charge balance equations to quantify the short-range borate structure in terms of the molar fractions X4m, X4o, X3, X2, X1 and X0 for borate units BØ4-, BØ2O23-, BØ3, BØ2O-, BØO22- and BO33-, where Ø and O- denote bridging and non-bridging oxygen atoms. Borate tetrahedral units were found to be present in both the meta-borate, BØ4-, and ortho-borate, BØ2O23-, forms with BØ4- constituting the dominating tetrahedral species for 0.20 ≤ x ≤ 0.70. The BØ2O23- units prevail at higher Bi2O3 levels (x > 0.7), and coexist with their isomeric triangular borate species BO33- (BØ2O23- ⇌ BO33-). The present IR results for the total molar fraction of borate tetrahedral units, X4 = X4m + X4o, are in very good agreement with reported NMR results for the fraction of boron atoms in four-fold coordination, N4. Besides evaluating X4m and X4o, the present work reports also for the first time the fractions of all types of triangular borate species X3-n with n = 0, 1, 2 and 3. The IR region below 550 cm-1 was found to be dominated by the Bi-O vibrational activity in coexisting ionic (160-230 cm-1) and distorted BiO6 sites (330-365 cm-1 and 475-510 cm-1), a result reflecting the dual role of Bi2O3 as glass-modifier and glass-former oxide. The latter role dominates in glasses exceeding 60 mol% Bi2O3, and is consistent with the extended glass formation in the bismuth-borate system. The structural results were used to calculate the average number of bridging B-Ø bonds per boron center, the average Bi-O and B-O single bond energy, and the atomic packing density of the studied glasses. These properties vary approximately linearly with Bi2O3 content in the three regimes 0.2 ≤ x ≤ 0.4, 0.4 < x ≤ 0.6 and 0.6 < x ≤ 0.83, and contribute collectively to the composition dependence of glass transition temperature.
Τίτλος πηγής δημοσίευσης:	Physical chemistry chemical physics : PCCP
Τόμος/Κεφάλαιο:	23
Τεύχος:	16
Σελίδες:	10006–10020
Θεματική Κατηγορία:	[EL] Φυσική και θεωρητική χημεία[EN] Physical and theoretical chemistry [EL] Φασματοσκοπία[EN] Spectroscopy [EL] Χημεία (Γενικά)[EN] Chemistry (General)
Λέξεις-Κλειδιά:	Bismuth Property–structure correlations Bismuth borate glasses
EU Grant identifier:	MIS 5002772 NSRF 2014–2020
Όροι και προϋποθέσεις δικαιωμάτων:	This article is Open Access.
Σημειώσεις:	EIK acknowledges support by the project ‘‘National Infrastructure in Nanotechnology, Advanced Materials and Micro-/Nanoelectronics’’ (MIS 5002772) which is implemented under the Action ‘‘Reinforcement of the Research and Innovation Infrastructure’’, funded by the Operational Programme ‘‘Competitiveness, Entrepreneurship and Innovation’’ (NSRF 2014–2020) and co-financed by Greece and the European Union (European Regional Development Fund).
Εμφανίζεται στις συλλογές:	Ινστιτούτο Θεωρητικής και Φυσικής Χημείας (ΙΘΦΧ) - Επιστημονικό έργο