An in-situ XANES investigation of the interactions between iron, manganese and antimony in silicate melts

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An in-situ XANES investigation of the interactions between iron, manganese and antimony in silicate melts ⁎

Anne-Isabelle Bidegaraya,b,c, , Andrea Cegliad, Maria Rita Cicconie, Van-Thai Phamf, Amandine Crabbéa, El Amine Mernissi Cheriguia, Karin Nysc, Herman Terryna, Daniel R. Neuvilleg, Stéphane Godetb a

Department of Electrochemical and Surface Engineering, SURF Research Group, Vrije Universiteit Brussel, 2 Pleinlaan, B-1050, Brussels, Belgium Materials Engineering, Characterization, Processing and Recycling, 4MAT, Université libre de Bruxelles, 50 Avenue Franklin Roosevelt, CP165/63, B-1050 Brussels, Belgium c Department of Art Sciences and Archaeology, MARI Research Group, Vrije Universiteit Brussel, Pleinlaan 2, B-1050, Brussels, Belgium d Department of Applied Physics and Photonics, Brussels Photonics Team B-PHOT, Vrije Universiteit Brussel, 2 Pleinlaan, B-1050 Brussels, Belgium e Department Werkstoffwissenschaften, Lehrstuhl für Glas und Keramik, Universität Erlangen-Nürnberg. Martensstrasse 5, D-91058, Erlangen, Germany f Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP48, 91192, Gif-sur-Yvette, France g Institut de Physique du Globe de Paris, CNRS, Géomatériaux, Sorbonne Paris Cité, 1, rue Jussieu, F- 75238 Paris, France b

A R T I C LE I N FO

A B S T R A C T

Keywords: Soda-lime silicate melts Redox reactions in-situ XANES Transition elements

The analysis of iron, manganese and antimony in silicate glass is of great interest in chemistry, materials science, earth sciences and archaeological sciences. Yet, conclusions from different fields appear to be contradictory and many questions about redox reactions in glass remain. The purpose of this study is thus to discuss whether and how these multivalent elements interact in glass. Soda-lime silicate melts containing iron along with manganese and/or antimony have been analysed at different high temperatures under argon atmosphere. Using in-situ XANES at the Fe K-edge, redox thermodynamics, kinetics and diffusivities have been assessed for the different compositions. The data obtained show that antimony is more efficient at oxidising iron compared to manganese at all temperatures. The oxidising power trend would thus be Sb > Sb + Mn > Mn. Furthermore, hypotheses on the formation of Fe-Mn complexes are also reported in glasses with stoichiometric proportions of iron and manganese. Based on the determination of redox diffusivities, it appears that presence of other multivalent elements does not significantly affect the iron redox mechanisms and that diffusivity is essentially controlled by the mobility of calcium.

1. Introduction Understanding oxidation-reduction reactions in glass is central to many different fields not only in the glass industry to control colour and fining [1] but also in geochemistry [2], nuclear waste management [3] and archaeology [4]. Indeed, antimony and manganese in glass have been used as decolouring agents since Antiquity to oxidise the reduced iron present as a sand impurity imparting a blue-green hue to the glass [5–7]. Manganese and antimony have actually been used until recently for the decolouration of glass [8], antimony playing the role of a fining agent [9,10]. The oxidation state of iron in glass depends on temperature, oxygen fugacity, chemistry of the glass (chemical composition and optical

basicity, both being intrinsically related) and has been widely investigated both in simplified or multicomponent systems [11,12]. Based on thermodynamic considerations, the higher the temperature is, the more reduced the iron, while the higher oxygen fugacity is, the more oxidised the iron is [11]. These aspects have been experimentally verified and modelled by several empirical investigations (e.g. Carmichael and co-workers [2,12–14]). The crucial influence of temperature on redox mechanisms has been demonstrated for glass containing iron (with different chemical compositions such as diopsidic, basaltic glass, borosilicates, soda-lime silicates): near the glass transition, the diffusion of divalent cations drives the redox reactions while, in contrast, at higher temperatures oxygen diffusion represents the dominant mechanism [15–17]. Redox mechanisms have recently been expanded

⁎ Corresponding author at: Department of Electrochemical and Surface Engineering, SURF Research Group, Vrije Universiteit Brussel, 2 Pleinlaan, B-1050, Brussels, Belgium. E-mail address: [email protected] (A.-I. Bidegaray).

https://doi.org/10.1016/j.jnoncrysol.2018.09.015 Received 9 July 2018; Received in revised form 25 August 2018; Accepted 8 September 2018 0022-3093/ © 2018 Elsevier B.V. All rights reserved.

Please cite this article as: Bidegaray, A.-I., Journal of Non-Crystalline Solids, https://doi.org/10.1016/j.jnoncrysol.2018.09.015

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synthesized using dried silicon dioxide as well as sodium and calcium carbonates and melted in a PteRh crucible at 1400 °C in air, alumina was not part of the original batch but came during the process of glassmaking (use of alumina-based mortar). The nominal concentration of iron was determined in order to have X-ray absorption edges of about 1 and to detect the X-ray Absorption Spectroscopy (XAS) signal in transmission mode based on X-ray absorbance calculations [32]. Fe2O3 along with Mn2O3 and/or Sb2O3 were thus added as oxides aiming to obtain the following glasses:

upon: cations such as sodium could also be the diffusing species which could rate-limit the redox reactions even in the high temperature domain [18,19]. Studies in chemistry, physics and earth sciences have sought to understand processes with one or more redox couple(s) [20–22]. Electrochemical methods, for example, have been successfully employed to characterise multivalent elements in glasses [10,23–25]. These direct analysis methods have allowed Schreiber and co-authors [20] to establish an electromotive force series for several multivalent elements in silicate glasses/melts in order to evaluate the oxidationreduction equilibrium when different redox couples are present in glassforming melts. The authors suggested that manganese is a more effective oxidising agent than antimony for glasses containing 1 wt% of the different multivalent elements for soda-lime-silicate compositions [20]. On the other hand, studies done on archaeological glasses ([7] and references therein) such as fragments of glass vessels, windows or production remains have led archaeologists to conclude that antimony is “a stronger decolourizer than manganese” [7]. A more recent study [26] on archaeological and synthetic glasses also report that antimony is a more effective oxidising agent than manganese. Beside the disagreement on the better oxidising agent, also the mechanisms involved in the reduction-oxidation reactions have been much debated. Indeed, some researchers argued that redox pairs do not interact in the melt and that this mutual interactions occurs only during quenching [22,27,28], whilst other studies experimentally proved and discussed that electrons can be exchanged at melt temperatures [29,30]. Therefore, there is the need to further characterise the possible interactions between these important multivalent elements: iron, manganese and antimony. In-situ dispersive X-ray absorption Near Edge Structure (XANES) spectroscopy could provide the necessary information, because it is an element selective technique, yet there are only a few studies so far concerning one or two redox couples at high temperatures [18,29]. In-situ dispersive XANES can be used not only to study redox equilibria but also to monitor the kinetics and redox mechanisms involved. The first study high temperature in-situ XANES study following the simultaneous evolution of two edges has recently been carried out by Cicconi et al. They showed that the redox reactions of iron and europium are sequential during reduction [29]. This indicates that if more than one redox couple is present, the different multivalent elements do not necessarily react together simultaneously. To our knowledge, no in-situ study of the redox reactions between iron, manganese and antimony has been carried out hitherto; the underlying mechanisms and kinetics thus remain unclear. This paper focuses on how the oxidation state of iron is influenced by the presence of antimony and/or manganese oxides, and how it evolves at different temperatures under argon atmosphere. This fundamental study is carried out in soda-lime silicates doped with iron, antimony and manganese. In-situ- XANES at the Fe K-edge enables to determine how and whether these three elements interact in the glassforming melt, as well as to track the kinetics and mechanisms of these redox reactions. Analyses are carried out for reductions in this case, however they can be generalised to oxidations since both processes are considered not to be significantly different [31]. The aim is to acquire a better understanding of the interactions of these elements in the glass-forming melt. First, the variations of Fe Xray Absorption Spectroscopy (XAS) absorption edges and Fe pre-edge peaks with temperature and chemical composition will be presented. Based on these features, we will then discuss redox equilibria, kinetics and mechanisms in a subsequent section.

• 4 mol% Fe O (Fe8), • 4 mol% Fe O and 4 mol% Mn O (Fe8Mn8), • 4 mol% Fe O and 2.2 mol% Mn O (Fe8Mn4), • 4 mol% Fe O and 4 mol% Sb O (Fe8Sb8), • 2 mol% Fe O , 2 mol% Mn O and 2 mol% Sb O 2

3

2

3

2

3

2

3

2

3

2

3

2

2

2

3

3

3

2

3

(Fe4Mn4Sb4).

Each glass was cast, crushed and re-melted three times to ensure homogeneity. The chemical compositions of the glasses (Table 1) were checked using Electron Probe Micro Analyzer CAMECA SX-FIVE equipped with a LaB6 gun, 5 WDS spectrometer and an EDS Brüker (EPMA). We used several mineral and metallic standards for quantification based on [33]; acceleration voltage was 15 kV, beam diameter 40 μm and beam current 20 nA, there was no sodium migration for these parameters. For each glass, 10 measurements were acquired and averaged, these confirmed the nominal compositions. In the case where the total sum was outside the range 98%-102%, the data point was discarded. The glass transition temperature was measured using Differential Scanning Calorimetry (STA409PC Luxx, Netzsch) with a cycle of heating-cooling-heating at 20 K/min in argon atmosphere in a PteRh 20 crucible with 20 mg of glass powder. The glass transition was determined within ± 3 K during the second heating step as the inflection of the glass transition region. Glass densities were measured at ambient temperature using Archimedes method. Reported densities are averaged over two measurements on 1–5 g samples ( ± 0.02 g/cm3). Because of the high content of transition elements, the homogeneity of all glasses was carefully checked. Indeed, if the concentrations of iron and manganese were higher than those studied here, crystallization of iron and manganese oxides can occur [34,35]. However, in this case, the absence of micro-crystalline phases was verified using powder X-ray Diffraction (Bruker D5000), optical microscope and Raman spectroscopy. 2.2. XANES data acquisition and treatment Fe and Mn K-edge X-ray Absorption Near Edge Structure (XANES) spectra have been collected at ODE beamline (SOLEIL Synchrotron, France), an energy dispersive beamline with a Si (311) polychromator providing a resolution ΔE/E of ~0.5 eV, at the Fe K-edge. The beam size was around 50 × 50 μm (FWHM, vertical and horizontal). Due to the fixed energy–position correlation in the selected energy range, a complete absorption spectrum was obtained from measurements of the intensity distribution on a position-sensitive detector. Moreover, since a spectrum can be recorded in the order of seconds, dispersive-XANES is particularly well suited to investigate kinetic processes at different temperatures. Transmission spectra were recorded from a metallic Fe reference foil and used to provide the energy calibration (inflection point at 7112.0 eV). The same was done from a Mn reference foil (inflection point at 6539.0 eV). Powdered glass samples were loaded in a 0.5 mm hole of the PtIr10% heating wire of a micro-furnace developed by Neuville et al. [36] and previously used for other in-situ XANES experiments [15,16,36,37]. The closed furnace allows the samples to be heated at controlled temperatures under different atmospheres. Given the geometry of the furnace (0.25 L) and the flow rate (2–3 L/min), it can be determined that the furnace would be filled in less than 10 s.

2. Methods 2.1. Glass preparation and characterization Simple soda-lime silicates were studied here to avoid the potential influence of minor oxides (Table 1). For each glass, a batch of 200 g was 2

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Table 1 Measured chemical compositions of the glasses (wt%), glass transition temperatures and glass densities (b.d. = below detection limit), between brackets composition in mol%.

Fe8 Fe8Mn4 Fe8Mn8 Fe8Sb8 Fe4Mn4Sb4

SiO2

Na2O

CaO

Fe2O3

69.04 ± 0.42 (72.84) 65.19 ± 0.28 (71.07) 62.1 ± 0.41 (69.37) 59.07 ± 0.58 (71.68) 62.60 ± 0.20 (71.73)

14.4 ± 0.13 (14.73) 13.74 ± 0.14 (14.52) 13.05 ± 0.15 (14.13) 11 ± 0.18 (12.94) 12.36 ± 0.07 (13.73)

7.41 ± 0.03 (8.38) 7.02 ± 0.05 (8.20) 7.07 ± 0.09 (8.46) 5.9 ± 0.08 (7.67) 6.62 ± 0.06 (8.13)

9.55 ± (3.79) 9.53 ± (3.90) 9.52 ± (4.00) 8.04 ± (3.67) 4.84 ± (2.09)

Mn2O3

Sb2O3

Al2O3

0.41

b.d.

b.d.

0.24

4.91 ± 0.12 (2.04) 8.91 ± 0.25 (3.80) b.d.

b.d.

0.43 ± (0.26) 0.41 ± (0.26) 0.37 ± (0.24) 0.34 ± (0.24) 0.29 ± (0.20)

0.25 0.20 0.15

4.59 ± 0.15 (2.00)

P1 A1 + P2 A2 A1 + A2

15.16 ± 0.16 (3.79) 9.01 ± 0.17 (2.12)

Density ( ± 0.02) (g/cm3)

0.02

837.4

2.58

0.02

824.3

2.65

0.01

821.4

2.71

0.03

811.2

2.78

0.03

818.2

2.73

reduced and most oxidised glasses within each series. Very similar results were obtained with both methods. The error associated to the ratios Fe3+/Fetot is taken as the 95% confidence interval around the mean of the centroid values once equilibrium has been reached (i.e. ± 0.03). For the glass containing manganese, spectra at the Mn K-edge (6539 eV) were recorded as well. However, despite some variations in the shape of the Mn XANES spectra, it was not possible to -provide a quantification of the Mn redox state.

During in-situ experiments, each sample was submitted to the same cycle of temperature increase and atmosphere changes. This means that, at a given temperature, redox equilibrium was first reached in air. Secondly, argon was injected until equilibrium was attained at that same temperature. Finally, air was injected again and, once equilibrium was reached, the temperature was increased. This cycle was repeated for several temperature steps. This study reports the kinetics and the redox ratios recorded during the second step, i.e. under argon atmosphere. The furnace atmosphere can influence the redox state of multivalent elements in glass-forming melts [38]. Therefore, to focus the study only on the interaction between multivalent elements and to limit the influence that oxygen from the furnace atmosphere could have, the reactions are followed in argon, which provides slightly reducing conditions (only ~8 ppm). It was considered that the glass was at a redox equilibrium when no change in the absorption edge was observed after at least 200 s. For each temperature step, we thus made sure to reach a plateau in the redox ratio. After calibration (by converting pixel position to energy) XANES signal was normalised at the Fe K-edge using first-order pre-edge and post-edge subtractions. Given the large number of spectra, an in-house Matlab programme was used. A few spectra per experiment were normalised with Athena® software [39] in order to compare the different normalization procedures and compare the chosen parameters. Beside the main edge, particular attention was paid to the pre-edge peak. This feature results from an 1 s →3d transition, partially allowed by the mixing of iron (d-state) and oxygen (p-state) and thus making it particularly sensitive to the redox state and the coordination of iron [40,41]. Using Igor Pro® software, the pre-edge was extracted using an arctangent baseline correction and fitted with two Voigt peaks, constrained to have a 50% Lorentzian and 50% Gaussian shape (FWHM between 1.3 and 1.6 eV) [42,43]. The centroid energy of the pre-edge (i.e. the energy position at which half of the total area is integrated) can be related to the average iron oxidation state in glass [44] and is determined using Eq. (1).

Centroid (eV) =

b.d.

Tg (K)

3. Results Fig. 1 shows the Fe K-edge XANES spectra for two different glasses (Fe8 and Fe8Sb8, respectively in Fig. 1a and Fig. 1b), collected both in argon atmosphere, but at two different temperatures: room temperature (RT – black lines) and in the liquidus (red lines). The black spectra in Fig. 1 are signals collected for samples at RT, and both shape and energy position of the edges are typical for glasses with prevalent Fe3+ species [40,44], and the pre-edge peak analysis confirmed that the majority of iron is in the oxidised form. Indeed, the estimated Fe3+/ Fetot ratios are 0.92 ± 0.03 and 0.96 ± 0.03, respectively for Fe8 and Fe8Sb8. The red spectra (Fig. 1) were collected at high temperatures (circa 1400 K), once redox equilibrium was reached (respectively after 660 s for Fe8 and after 650 s for Fe8Sb8). The spectrum collected for the Fe8 melt (Fig. 1a) is clearly shifted at lower energies, whereas the

(1)

with A1 and A2 the integrated peak areas of the two Voigt functions and P1 and P2 peak positions (eV). XANES signals, and in turn, the centroid energy positions were determined also for reference crystalline materials: for staurolite, an [4]Fe2+ model compound, the estimated centroid position is 7113.11 ± 0.03 eV, whereas, for aegirine (6-fold coordinated Fe3+ model compound) is 7114.62 ± 0.03 eV. These values are in agreement with the literature [40,43,45]. Based on these centroid values, and following the work of Wilke [40], a mixing line between these two end-members was calculated, and used to quantify the Fe redox ratios in all the glass samples. Since experiments done at high temperatures could modify the intensity of the XANES features, in order to validate the method used for the centroid determination, we considered an alternative approach for the pre-edge peak analysis, where the mixing lines between the two end-members were based on the most

Fig. 1. Normalised XANES spectra at equilibrium under argon atmosphere of a. Fe8 at room temperature (black) and 1403 K (red, dotted lines), b. Fe8Sb8 at room temperature (black) and 1412 K (red, dotted lines). The edge position shifts as iron redox changes. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) 3

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Measurements at higher temperatures for Fe8 were also carried out. However, due a reason unknown to us, the data is very noisy and thus cannot be used. The data shown here for Fe8 thus provides a basis for the comparison with other glasses at other chemical compositions. Apart from equilibria, it is also possible to analyse the time evolution of the iron redox state. An example is given in Fig. 3 for Fe8 at four different times (0 s, 64 s, 233 s and 980 s). It appears clearly in Fig. 3 that iron becomes more reduced as time passes, since the contribution at lower energies in the pre-edge peaks rises. The redox ratio thus decreases from 0.95 initially to 0.84 after 64 s, 0.72 after 233 s and 0.66 at equilibrium ( ± 0.03). No more changes in the XANES spectra and in the relative pre-edge peaks (i.e. Fe redox ratio) were observed after 660 s. Fig. 4 shows three spectra collected at the Mn K-edge for the composition Fe8Mn8, at 1386 K, and at different times (2 s, 67 s and 1667 s). No significant variation in the absorption edge position is observed so that there does not seem to be a change in manganese redox ratio. However, the spectral shapes are slightly evolving thus suggesting a potential change in the local environment.

Fig. 2. Pre-edge peaks of normalised XANES spectra of all the glasses under argon atmosphere at room temperature from the glass as synthesized (black spectra, left) and high temperature (red spectra, right), subtracted from the background, along with the fitting (full line), the two Voigt functions (dotted lines) and the estimated Fe3+/Fetot ( ± 0.03). The iron reduction at high temperatures is dependent on the presence of other multivalent elements. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

4. Discussion and assumptions 4.1. Redox equilibria Even though glass chemical composition can have a crucial influence on the iron redox ratio [12,46,47], the redox variations observed here cannot be attributed to compositional effects. Indeed, the theoretical optical basicity for the five glasses studied here is around 0.59 (based on values given in [48]). Using the model developed by Duffy [49], this would lead to all glasses having a redox ratio between 0.81 and 0.83. The evolution of the redox ratio of iron with temperature in glasses doped with iron and co-doped with manganese and/or antimony is given in Fig. 5. As expected, there is a straight-line relationship that describe the temperature dependence of redox equilibria: the Fe2+/Fe3+ ratio varies linearly with reciprocal temperature and the slope varies with composition [50–52]. The slopes of the log(Fe2+/Fe3) as a function of reciprocal temperature fall within the range −0.2 to −0.8. Mysen and Virgo [52] obtained slopes in a similar range from Mossbauer measurements on Fe-bearing soda-lime silicates although they had been

Fe8Sb8 melt (Fig. 1b), where both Fe and Sb are present, presents a smaller shift compared to the melt containing only Fe. The estimated redox ratios (Fe3+/Fetot) are 0.66 ± 0.03 and 0.70 ± 0.03, respectively for Fe8 and Fe8Sb8. In order to quantify the redox ratio of iron, the pre-edge peak is analysed as can be seen on Fig. 2 for all the glasses and melts studied. Fig. 2 shows the background subtracted pre-edge peak at room temperature (black spectra, left) and at one high temperature (red spectra, right) for all glass compositions analysed. For all glass compositions, the iron is more reduced at high temperatures. While at room temperature all glasses are almost fully oxidised, it appears that the presence of other multivalent elements has a more important impact at high temperature. The same trend is observed at other temperatures as can be seen in Table 2 where the amount of Fe2+ and Fe3+ is also given.

Table 2 Measured glass chemical composition, dopant amount, final redox ratio at equilibrium, centroid and edge positions and characteristic times derived from Eq. 2 (see section 4.2). Sample

Temperature (K)

Fe3+/Fetot at equilibrium ( ± 0.03)

Centroid (eV) ( ± 0.03)

Edge position (eV) ( ± 0.25)

τ (s)

Fe3+ (mol)

Fe2+ (mol)

Fe8 7.7 mol% Fe Fe8Mn4 7.8 mol% Fe 4.0 mol% Mn

1331 1403 1300 1448 1526 1688 1324 1378 1431 1484 1535 1585 1274 1342 1412 1483 1556 1631 1732 1298 1417

0.80 0.66 0.75 0.66 0.67 0.53 0.53 0.48 0.42 0.39 0.40 0.35 0.85 0.74 0.70 0.65 0.60 0.53 0.40 0.72 0.58

7114.24 7114.03 7114.17 7114.03 7114.04 7113.83 7113.84 7113.76 7113.67 7113.62 7113.64 7113.56 7114.32 7114.15 7114.09 7114.01 7113.94 7113.83 7113.64 7114.12 7113.91

7122.89 7119.61 7122.77 7121.58 7118.77 7118.78 7118.84 7118.82 7118.81 7118.55 7118.31 7117.41 7122.98 7122.75 7121.89 7119.86 7119.81 7118.68 7118.8 7122.91 7119.1

167.5 144 458 161.7

6.16 5.08 5.85 5.15 5.23 4.13 4.24 3.84 3.36 3.12 3.20 2.80 6.38 5.55 5.25 4.88 4.50 3.98 3.00 2.88 2.32

1.54 2.62 1.95 2.65 2.57 3.67 3.76 4.16 4.64 4.88 4.80 5.20 1.13 1.95 2.25 2.63 3.00 3.53 4.50 1.12 1.68

Fe8Mn8 8.0 mol% Fe 7.7 mol% Mn

Fe8Sb8 7.5 mol% Fe 7.5 mol% Sb

Fe4Mn4Sb4 4.0 mol% Fe 3.9 mol% Mn 4.1 mol% Sb

4

118 271.5

82.4 68.2 226.9 216 142.6 144 98.7 65.1 753.9 323.8

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Fig. 3. Pre-edge of normalised XANES spectra under argon atmosphere of Fe8 at a temperature of 1403 K at 0, 64, 233 and 980 s, subtracted from the background, along with the Voigt peaks used for the fitting and the estimated Fe3+/Fetot showing iron reduction with time.

point of view and it has been modelled that the higher the temperature, the more reduced the iron will become [12,53]. Although we have only two data points, the evolution of Fe8 behaves accordingly as can be observed in Fig. 5. Conversely antimony and manganese containing glass have not been extensively studied and modelled hitherto, yet the trend is the same, i.e. higher temperatures led to higher amounts of reduced iron species. In Fig. 5a the iron redox ratios estimated for the different temperatures are reported for all samples: compositions where iron and antimony or iron and manganese are in stoichiometric proportions (Fe8Sb8 and Fe8Mn8 respectively), where there is twice as much iron than manganese (Fe8Mn4), and where iron, manganese and antimony are all present in stoichiometric proportions (Fe4Mn4Sb4). It is clearly observed that in Fe8Sb8 or Fe8Mn4, the iron is more oxidised than in Fe8Mn8 or in Fe4Mn4Sb4 (see Table 2). For centuries, it has been considered that antimony and manganese are oxidising agents for iron; antimony and manganese were already used in antiquity as decolouring agent by oxidising iron (present as an impurity) from its bluish reduced form to its yellowish-colourless oxidised form [7,8,54]. Schreiber et al. [20] predicted the oxidation of iron by antimony and manganese using an electromotive force series where the order of relative reduction potential is Mn3+-Mn2+ > Sb5+Sb3+ > Fe3+-Fe2+ in air for glasses containing 1 wt% iron, manganese or antimony. Due to experimental limitations, only two points for Fe8 could be very safely obtained. Based on those points and the slope that could be determined, we could speculate that in the lower range of temperatures analysed (i.e. below 1350 K), the presence of multivalent elements does not efficiently oxidise the iron. However, the data

Fig. 4. Normalised XANES spectra at the Mn-edge and magnification of the preedge peaks for Fe8Mn8 at 1386 K at three different times: in green, at the start of the measurement, in blue: 67 s after the start of the measurement, in dotted lines: at equilibrium, after 1667 s. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

quenched. Furthermore, it is interesting to note that both manganese melt compositions (Fe8Mn8 and Fe8Mn4) have similar slopes (respectively −0.23 and − 0.24), as well as both Sb-bearing compositions (Fe8Sb8 and Fe8Mn4Sb4), with slope of −0.40, and − 0.41, respectively. Based on previous research, it is known from a thermodynamical

Fig. 5. a. Temperature evolution of the oxidation state for the different melt compositions, under argon atmosphere. A typical Arrhenian behaviour is observed. b. Iron redox ratio, as Fe3+/Fetot as a function of temperature where the order of the more effective oxidising agent can be observed. Dotted lines are only guides for the eyes.

5

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deviations from the expected reduction potential trend. Indeed, they observed that in glasses containing higher concentrations of iron, manganese became a less effective oxidising agent. This could be explained by considering the stabilization of MneFe complex in the melt [54,57]. In our soda-lime silicate compositions, with iron and manganese in stoichiometric proportions (Fe8Mn8), it is reasonable to think that a similar mechanism occurs, where the formation of FeeMn clusters would decrease the amount of manganese available as a potential oxidiser. We hypothesize that FeeMn clusters form when iron and manganese are present in a stoichiometric ratio (Fe8Mn8) whereas this is either not the case or to a lesser extent if there is twice as much iron as manganese (Fe8Mn4). Metal to metal clusters have already been observed and studied for iron [58] and for manganese [59]. It has been suggested that the FeeMn cluster requires energy so that the higher the temperature is, the easier it is for these clusters to form [54]. It would be expected that these clusters would affect the structure of the glass and thus the XAS spectra. However, the XANES spectra recorded here do not show such variations as thermal broadening has surely an effect both on the XANES region and also on the first oscillations in the extended energy region. On the other hand, such clusters do not seem to form between iron and antimony. Even though this remains a hypothesis, this could be related to the fact that antimony is a fining agent (Fig. 5b), thought to act by the decomposition of antimony oxide thus releasing oxygen in the melt [9]. The presence of different multivalent elements affects the redox ratio of iron in the melt. This indicates that there must be some interaction between the different redox couples in the melt, i.e. in the glassforming melt. This supports the idea that electrons are also exchanged in the silicate melt [29,30].

Fig. 6. Time evolution of the iron oxidation states in argon, a. Fe8Sb8, b. Fe8 for different temperatures, comparing characteristic times with temperatures.

dispersion and the availability of only two points for the Fe8 composition hamper any further consideration. On the other hand, samples where iron and antimony or manganese are present in stoichiometric proportions (Fe8Sb8 and Fe8Mn8, respectively), together with those where iron, manganese and antimony are all present in stoichiometric proportions (Fe4Mn4Sb4) do show a clear trend (Fig. 5b). In terms of controlling the iron oxidation state, it is possible to observe that the order is Sb > Sb + Mn > Mn for composition where iron is in stoichiometric proportions with another multivalent element. In the case where there is twice as much iron as manganese (Fe8Mn4), the iron has similar oxidation states as for a glass with stoichiometric proportions of iron and antimony (Fe8Sb8).The lower iron redox ratio (Fe3+/Fetot) for the compositions with iron and both manganese and antimony (Fe4Mn4Sb4) and iron and manganese in stoichiometric proportions (Fe8Mn8) is observed for all the temperatures here investigated. Since sample Fe4Mn4Sb4 contains less iron than the other compositions, and twice the amount of other multivalent elements, the oxidising power trend observed Sb > Sb + Mn > Mn could be unexpected. However, it is reasonable to think that antimony and manganese, both having higher reduction potentials than Fe, interact with each other, and only partially oxidise iron [55], thus providing the clear tendency observed in Fig. 5. Based on stoichiometric considerations, it would be expected that one mole of iron reacts with one mole of manganese but that two moles of iron would react with antimony. From Table 2, it can be seen that some Fe2+ is always left at equilibrium for all the glasses. Furthermore, the proportion of Fe2+ towards Fe.3+ increases at higher temperature. This indicates that oxidations of iron by manganese and/or antimony are not total and are dependent on the melting temperature. Even though iron is present in stoichiometric proportions with either manganese or antimony, it does not lead to its full oxidation in those conditions. Yet these considerations are only valid regarding the electron exchange, iron coordination is also an important aspect that should be taken into account [56]. Based upon the series of reduction potentials reported by Schreiber [20] manganese should be the most effective oxidising agent for iron, in soda-lime silica glasses. However, Donald et al. [54] also reported

4.2. Redox kinetics The time evolution of the iron redox ratio can be fitted by Eq. (2) introduced by Magnien et al. [15].

(rt − re ) = (r0 − re ) e−t / τ

(2)

where rt is the redox ratio at time t, r0 and re the initial and equilibrium redox ratios and τ a characteristic time of the redox reaction determined from a least square fit. Fig. 6 shows the experimental data (dots) and the fit (solid lines) obtained at different temperatures for the reduction of samples Fe8Sb8, and Fe8 (respectively in Fig. 6a and b). This allowed τ to be determined for different temperatures, based on a least-square fit (data reported in Table 2). It was not possible to determine the τ for all experiments. For all experiments and compositions, the redox ratio of iron is linearly dependent from the square root of time. This supports the wellestablished mechanism of redox reaction which is attributed to diffusion [27,31,60]. The time taken to change atmosphere in the furnace cannot be considered as determining the rate of the reaction because it takes less than 10 s to change the furnace atmosphere, one order of magnitude less that the characteristic reaction times. An Arrhenian temperature dependence can be observed for the characteristic times (Fig. 7). As expected, for all glasses, the higher the temperature is, the smaller the characteristic times are and thus the faster the redox reactions occur. First, it is interesting to note that the presence of one or more multivalent element does not lead to major differences in the kinetics: for any temperature, the characteristic times differ by less than one order of magnitude (Fig. 7). This can be directly related to the study of Magnien et al. [31] about the influence of different alkali cations in silicates where it was shown that the chemical composition plays a more important role at lower temperatures, around the glass transition. If clusters appear and change the redox equilibria, they do not seem to modify markedly the kinetics at the temperatures studied here. In details, the presence of any oxidising agent (antimony and/or manganese) slows down the reduction kinetics (Fig. 7). In particular, the iron 6

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Fig. 8. Redox diffusivities of Fe8, Fe8Mn8, Fe8Mn4, Fe8Sb8 and Fe4Mn4Sb4 under argon atmosphere as a function of temperature compared to literature data under air atmosphere. Reported literature data: Ca2+ for jadeite and albite composition [65], Na for an obsidian composition [66], Fe2+ in a Na2O-FeOAl2O3-SiO2 composition [67], O2– diffusion calculated with Eyring relation from the viscosities of NCS (soda-lime silicate) (grey dashed line) [68], O2 in CaOMgO-2SiO2 (grey full line) [69], NS2F5 measured redox diffusivities (sodadisilicate with 5 mol% FeO) [18,70].

Fig. 7. Temperature evolution of the characteristic time (τ) of iron reduction under argon atmosphere, for all the compositions show an Arrhenian behaviour. The error bars refer to the acquisition of τ based on a least square fitting.

reduction is the slowest one when both antimony and manganese are present (Fe4Mn4Sb4). In the case of glasses with iron and manganese, the reduction goes faster if iron and manganese are in stoichiometric proportions (Fe8Mn8) than if there is twice as much iron as manganese (Fe8Mn4). Comparing this to the redox equilibria, it seems that the more the iron get reduced in the glass-forming melt, the faster this reduction occurs [15,18].

Furthermore, there is no marked difference between the glass containing antimony and the other glasses in this range of temperatures. Even though antimony is a fining agent in the glass-forming melt, this does not seem to translate into a different redox mechanism. For comparative analysis, literature data on redox diffusivity are reported for NS2F5 (62.1 wt% SiO2, 32.0 wt% Na2O, 5.84 wt% FeO) [18]. Larger differences would be expected at lower temperatures [18]. We propose that the differences in redox diffusivities between Fe8 (glass containing iron only) and NSF5 are mainly due to the presence of calcium in Fe8. Indeed, NS2F5 does not contain calcium, so that the dominant mechanism of redox reactions can be attributed mainly to the diffusion of sodium and oxygen. Yet, the role of calcium in glass is complex as it can behave differently depending on the glass composition [37]. It is possible that the atmosphere has an influence as the diffusivities of NS2F5 were measured in air so that the oxygen from air can interfere whereas in this study, measurements were carried out in a controlled atmosphere (argon) thus the possible interactions between silicate melts and oxygen are limited.

4.3. Redox diffusivities The redox diffusivity Dr was first used to determine diffusion coefficients in silicate glasses by Lamkin et al. [61] with a theoretical background outlined by Crank [62,63]. It allows the characteristic times to be compared for samples exhibiting different geometries. Moreover, it also provides useful insights into the redox mechanisms. The redox diffusivity Dr is calculated using Eq. (3) (Eyring relation).

Dr =

r2 4teq

(3)

where r is the thickness of the sample and is determined using the experimental absorption edge jump Δμ [64]. teq is defined as the time needed to reach 99% of the equilibrium redox ratio and is given by Eq. (4).

teq = −τ. ln(0.01)

5. Conclusions

(4)

The influence of antimony and manganese on the redox equilibrium, kinetics and mechanisms of iron has been investigated using in-situ XANES, at the Fe K-edge. Antimony is an oxidising agent of iron for any temperature while manganese does not act as an oxidising agent, at least if there is as much iron as manganese. We suggest that this comes from the formation of Fe-Mn clusters which impedes manganese to play the role of the oxidising agent so that iron gets more reduced than if it was present by itself. Therefore, in glass with as much manganese as iron, iron is less oxidised than in glass containing twice less manganese. Whether the observed variations of the redox states at equilibrium and the formation of clusters are related to the redox mechanisms and kinetics is an important question. Thanks to in-situ XANES experiments, this aspect could also be discussed. Actually, the redox mechanisms are mostly affected by the presence of calcium in the glass compared to other glasses from the literature. Yet, the reduction mechanisms do not differ significantly between the different samples studied here even though their iron redox states at equilibrium vary. We propose that the presence of clusters still affects the redox state of iron at equilibrium compared to a Mn-free glass-forming melt. However, the present data

In Fig. 8, the redox diffusivities, calculated based on the determination of teq for the glasses investigated here, are compared to literature data [16,18,65]– [68]. The redox diffusivities determined for each glass at a given temperature can be compared to the chemical diffusion of oxygen and the other cations of the melt in order to determine the rate limiting steps [15,31]. The redox diffusivities of glass from the literature were measured in air, while those of Fe8, Fe8Sb8, Fe8Mn8, Fe8Mn4 and Fe4Mn4Sb4 were determined under argon atmosphere. In this case (argon atmosphere, temperature range), the redox diffusivities are closest to the diffusivity of calcium. As proposed by Magnien et al. [31] and Neuville [71], calcium plays a key role which is facilitated by the presence of sodium. The mobility of calcium and to some extent the presence of sodium thus control diffusivity. It is worth noting that the redox diffusivities of the 5 glasses studied here do not differ markedly: for a certain temperature range, they remain within the same orders of magnitude. Thus, if Fe-Mn clusters are indeed formed in Fe8Mn8, there is no impact on the redox mechanisms. 7

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indicate that, if clusters are present, they have no effects on iron redox mechanisms and kinetics.

354–362. [29] M.R. Cicconi, D.R. Neuville, I. Tannou, F. Baudelet, P. Floury, E. Paris, G. Giuli, Competition between two redox states in silicate melts: an in-situ experiment at the Fe K-edge and Eu L3-edge, Am. Mineral. 100 (4) (2015) 1013–1016. [30] H.D. Schreiber, L.J. Peters, J.W. Beckman, C.W. Schreiber, Redox chemistry of ironmanganese and iron-chromium interactions in soda lime silicate glass melts, Glas. Sci. Technol. 69 (9) (1996) 269–277. [31] V. Magnien, D.R. Neuville, L. Cormier, J. Roux, J.-L. Hazemann, D. de Ligny, S. Pascarelli, I. Vickridge, O. Pinet, P. Richet, Kinetics and mechanisms of iron redox reactions in silicate melts: the effects of temperature and alkali cations, Geochim. Cosmochim. Acta 72 (8) (Apr. 2008) 2157–2168. [32] M. Alain, M. Jacques, M.-B. Diane, P. Karine, MAX: Multiplatform applications for XAFS, J. Phys. Conf. Ser. 190 (2009) 012034. [33] A. Ceglia, P. Cosyns, K. Nys, H. Terryn, H. Thienpont, W. Meulebroeck, Late antique glass distribution and consumption in Cyprus: a chemical study, J. Archaeol. Sci. 61 (2015) 213–222. [34] R. Harizanova, I. Gugov, C. Rüssel, D. Tatchev, V.S. Raghuwanshi, A. Hoell, Crystallization of (Fe, Mn)-based nanoparticles in sodium-silicate glasses, J. Mater. Sci. 46 (22) (2011) 7169–7176. [35] R. Harizanova, G. Völksch, C. Rüssel, Crystallization and microstructure of glasses in the system Na 2O/MnO/SiO2/Fe2O3, Mater. Res. Bull. 46 (1) (2011) 81–86. [36] D.R. Neuville, L. Hennet, P. Florian, D. De Ligny, In situ high-temperature experiments, Rev. Mineral. Geochem. 78 (2014) 779–800. [37] M.R. Cicconi, D. De Ligny, T. Gallo, D.R. Neuville, Ca neighbors from XANES spectroscopy: a tool to investigate structure, redox, and nucleation processes in silicate glasses, melts, and crystals, Am. Mineral. 101 (5) (2016) 1232–1235. [38] H.A. Schaeffer, T. Frey, I. Löh, F.G.K. Baucke, Oxidation state of equilibrated and non-equilibrated glass melts, J. Non-Cryst. Solids 49 (1–3) (1982) 179–188. [39] B. Ravel, M. Newville, ATHENA, ARTEMIS, HEPHAESTUS: Data analysis for X-ray absorption spectroscopy using IFEFFIT, J. Synchrotron Radiat. 12 (4) (2005) 537–541. [40] M. Wilke, F. Farges, P.E. Petit, G.E. Brown, F. Martin, Oxidation state and coordination of Fe in minerals: an FeK- XANES spectroscopic study, Am. Mineral. 86 (5–6) (2001) 714–730. [41] G. Calas, J. Petiau, Coordination of iron in oxide glasses through high-resolution Kedge spectra: Information from the pre-edge, Solid State Commun. 48 (7) (1983) 625–629. [42] A. Ceglia, G. Nuyts, S. Cagno, W. Meulebroeck, K. Baert, P. Cosyns, K. Nys, H. Thienpont, K. Janssens, H. Terryn, A XANES study of chromophores: the case of black glass, Anal. Methods 6 (8) (2014) 2662. [43] A. Ceglia, G. Nuyts, W. Meulebroeck, S. Cagno, A. Silvestri, A. Zoleo, K. Nys, K. Janssens, H. Thienpont, H. Terryn, Iron speciation in soda-lime-silica glass: a comparison of XANES and UV-vis-NIR spectroscopy, J. Anal. At. Spectrom. 30 (7) (2015) 1552–1561. [44] A.J. Berry, H.S. C, K.D. O'Neill, S.J. Campbell Jayasuriya, G.J. Foran, XANES calibrations for the oxidation state of iron in a silicate glass, Am. Mineral. 88 (7) (2003) 967–977. [45] G. Giuli, E. Paris, K.U. Hess, D.B. Dingwell, M.R. Cicconi, S.G. Eeckhout, K.T. Fehr, P. Valenti, XAS determination of the Fe local environment and oxidation state in phonolite glasses, Am. Mineral. 96 (2011) 631–636. [46] A. Borisov, H. Behrens, F. Holtz, Effects of strong network modifiers on Fe3+/ Fe2+ in silicate melts: an experimental study, Contrib. Mineral. Petrol. 172 (5) (2017) 34. [47] M.R. Cicconi, G. Giuli, W. Ertel-Ingrisch, E. Paris, D.B. Dingwell, The effect of the [Na/(Na+K)] ratio on Fe speciation in phonolitic glasses, Am. Mineral. 100 (7) (2015) 1610–1619. [48] V. Dimitrov, T. Komatsu, An interpretation of optical properties of oxides and oxide glasses in terms of the electronic ion polarizability and average single bond strength (review), J. Univ. Chem. Technol. Metall. 45 (3) (2010) 219–250. [49] J.A. Duffy, A review of optical basicity and its applications to oxidic systems, Geochim. Cosmochim. Acta 57 (16) (1993) 3961–3970. [50] W.D. Johnston, Oxidation-Reduction Equilibria in Molten Na2O.SiO2 glass, J. Am. Ceram. Soc. 48 (4) (1964) 0–6. [51] B.O. Mysen, Redox equilibria and coordination of Fe2+ and Fe3+ in silicate glasses from 57Fe mossbauer spectroscopy, J. Non-Cryst. Solids 95–96 (PART 1) (1987) 247–254. [52] B.O. Mysen, D. Virgo, Redox equilibria, structure, and properties of Fe-bearing aluminosilicate melts: Relationships among temperature, composition, and oxygen fugacity in the system Na2O-Al2O3-SiO2-Fe-O, Am. Mineral. 74 (1989) 58–76. [53] V.C. Kress, I.S.E. Carmichael, The compressibility of silicate liquids containing Fe2O3 and the effect of composition, temperature, oxygen fugacity and pressure on their redox states, Contrib. Mineral. Petrol. 108 (1991) 82–92. [54] S.B. Donald, A.M. Swink, H.D. Schreiber, High-iron ferric glass, J. Non-Cryst. Solids 352 (2006) 539–543 no. February. [55] C. Stalhandske, The impact of refining agents on glass colour, Glastek. Tidskr. 55 (3) (2000) 65–71. [56] B.O. Mysen, P. Richet, Silicate Glasses and Melts, Vol. 10 (2005). [57] H.D. Schreiber, G.B. Balazs, V. El, An electromotive force series for redox couples in a borosilicate melt: the basis for electron exchange interactions of the redox couples, J. Non-Cryst. Solids 71 (1985) 59–67. [58] P.A. Bingham, J.M. Parker, T. Searle, J.M. Williams, K. Fyles, Redox and clustering of iron in silicate glasses, J. Non-Cryst. Solids 253 (1–3) (Aug. 1999) 203–209. [59] D. Möncke, D. Ehrt, E.I. Kamitsos, Spectroscopic study of manganese-containing borate and borosilicate glasses: cluster formation and phase separation, Phys. Chem. Glasses Eur. J. Glass Sci. Technol. B 54 (1) (2013) 42–51. [60] G.T. Cook, R.F. Cooper, Iron concentration and the physical processes of dynamic

Acknowledgements This research was supported by a PhD fellowship by the Research Foundation – Flanders (Fonds voor Wetenschappelijk Onderzoek, FWO), grant number 11Z8417N. The authors also want to thank SOLEIL synchrotron and ODE beamline for their support (proposal n° 20150116). The authors declare no competing financial interest. References [1] M.-H. Chopinet, D. Lizarazu, C. Rocanière, L'importance des phénomènes d'oxydoréduction dans le verre, Comptes Rendus Chim. 5 (12) (2002) 939–949. [2] I.S.E. Carmichael, The redox states of basic and silicic magmas: a reflection of their source regions? Contrib. Mineral. Petrol. 106 (2) (1991) 129–141. [3] O. Pinet, I. Hugon, S. Mure, Redox Control of Nuclear Glass, Procedia Mater. Sci. 7 (2014) 124–130. [4] C. Moretti, S. Hreglich, Raw Materials, Recipes and Procedures Used for Glass Making, in: K. Janssens (Ed.), Modern Methods for Analysing Archaeological and Historical Glass, John Wiley, 2013, pp. 23–47. [5] E. Gliozzo, The composition of colourless glass: a review, Archaeol. Anthropol. Sci. 9 (4) (2017) 455–483. [6] A. Ceglia, P. Cosyns, K. Nys, H. Terryn, H. Thienpont, W. Meulebroeck, Light through glass: the spectrum of late Antique glass from Cyprus, J. Archaeol. Sci. Rep. 7 (2016) 614–624. [7] C.M. Jackson, Making colourless glass in the Roman period, Archaeometry 47 (4) (2005) 763–780. [8] G. Bontemps, Guide du verrier: traité historique et pratique de la fabrication des verres, cristaux, vitraux, Librairie. Paris, 1868. [9] H. Muller-Simon, Fining of Glass Melts, Rev. Mineral. Geochem. 73 (1) (Jun. 2011) 337–361. [10] M. Yokozeki, T. Moriyasu, H. Yamashita, T. Maekawa, Electrochemical studies of the redox behavior of antimony ions in sodium borate and silicate melts, J. NonCryst. Solids 202 (3) (1996) 241–247. [11] H.D. Schreiber, Redox processes in glass-forming melts, J. Non-Cryst. Solids 84 (1–3) (Jul. 1986) 129–141. [12] V.C. Kress, I.S.E. Carmichael, Stoichiometry of the iron oxidation reaction in silicate melts, Am. Mineral. 73 (1988) 1267–1274. [13] A. Kilinc, I.S.E. Carmichael, M.L. Rivers, R.O. Sack, The ferric-ferrous ratio of natural silicate liquids equilibrated in air, Contrib. Mineral. Petrol. 83 (1–2) (1983) 136–140. [14] R.O. Sack, I.S.E. Carmichael, M. Rivers, M.S. Ghiorso, Ferric-ferrous equilibria in natural silicate liquids at 1 bar, Contrib. Mineral. Petrol. 75 (4) (1981) 369–376. [15] V. Magnien, D.R. Neuville, L. Cormier, J. Roux, J.L. Hazemann, O. Pinet, P. Richet, Kinetics of iron redox reactions in silicate liquids: a high-temperature X-ray absorption and Raman spectroscopy study, J. Nucl. Mater. 352 (2006) 190–195. [16] B. Cochain, D.R. Neuville, D. De Ligny, J. Roux, F. Baudelet, E. Strukelj, P. Richet, Kinetics of iron redox reaction in silicate melts: a high temperature Xanes study on an alkali basalt, J. Phys. Conf. Ser. 190 (Nov. 2009) 012182. [17] M. Roskosz, M.J. Toplis, D.R. Neuville, B.O. Mysen, Quantification of the kinetics of iron oxidation in silicate melts using Raman spectroscopy and assessment of the role of oxygen diffusion, Am. Mineral. 93 (11–12) (2008) 1749–1759. [18] B. Cochain, D.R. Neuville, D. De Ligny, M. Malki, D. Testemale, O. Pinet, P. Richet, Dynamics of iron-bearing borosilicate melts: Effects of melt structure and composition on viscosity, electrical conductivity and kinetics of redox reactions, J. NonCryst. Solids 373–374 (2013) 18–27. [19] A. Pommier, F. Gaillard, M. Pichavant, Time-dependent changes of the electrical conductivity of basaltic melts with redox state, Geochim. Cosmochim. Acta 74 (5) (2010) 1653–1671. [20] H.D. Schreiber, N.R. Wilk, C.W. Schreiber, Comprehensive electromotive force series of redox couples in soda-lime-silicate glass, J. Non-Cryst. Solids 253 (1–3) (1999) 68–75. [21] F. Farges, Ab initio and experimental pre-edge investigations of the Mn K -edge XANES in oxide-type materials, Phys. Rev. B - Condens. Matter Mater. Phys. 71 (2005) 1–14. [22] A.A. Borisov, Mutual interaction of redox pairs in silicate melts: V5+/V4+/V3+/ V2+ tetrad and other equilibria, Petrology 21 (4) (Jul. 2013) 305–315. [23] K. Takahashi, Y. Miura, Electrochemical studies on ionic behavior in molten glasses, J. Non-Cryst. Solids 80 (1–3) (1986) 11–19. [24] C. Rüssel, E. Freude, Voltammetric studies in a soda-lime-silica glass melt containing two different polyvalent ions, Glas. Berichte 63 (6) (1990) 149–153. [25] O. Claußen, C. Rüssel, Thermodynamics of various polyvalent main group elements in a borosilicate glass melt, J. Non-Cryst. Solids 209 (1997) 292–298. [26] R. Arletti, S. Quartieri, I.C. Freestone, A XANES study of chromophores in archaeological glass, Appl. Phys. A Mater. Sci. Process. 111 (1) (Apr. 2013) 99–108. [27] C. Rüssel, Redox reactions during cooling of glass melts-a theoretical consideration, Glas. Ber 62 (2) (1989) 199–203. [28] A. Paul, Oxidation-reduction equilibrium in glass, J. Non-Cryst. Solids 123 (1990)

8

Journal of Non-Crystalline Solids xxx (xxxx) xxx–xxx

A.-I. Bidegaray et al.

[61] [62] [63] [64]

[65]

[66] A. Jambon, J.P. Carron, Diffusion of Na, K, Rb and Cs in glasses of albite and orthoclase composition, Geochim. Cosmochim. Acta 40 (8) (1976) 897–903. [67] W. Koehler, G.H. Frishat, Iron and sodium self diffusion in silicate glasses, Phys. Chem. Glasses 19 (1978) 103–107. [68] R. Terai, Y. Oishi, Self-Diffusion of Oxygen in Soda-Lime-Silicate Glass, Glas. Berichte 50 (4) (1977) 68–73. [69] K.W. Semkow, L.A. Haskin, Concentrations and behavior of oxygen and oxide ion in melts of composition CaO · MgO · xSiO2, Geochim. Cosmochim. Acta 49 (9) (1985) 1897–1908. [70] B. Cochain, Cinétique et mécanismes d'oxydoréduction dans les silicates fondus, Université Pierre et Marie Curie, 2009. [71] D.R. Neuville, Viscosity, structure and mixing in (Ca, Na) silicate melts, Chem. Geol. 229 (1–3) (2006) 28–41.

oxidation in an alkaline earth aluminosilicate glass, Am. Mineral. 85 (2000) 397–406. M.a. Lamkin, F.L. Riley, R.J. Fordham, Oxygen mobility in silicon dioxide and silicate glasses: a review, J. Eur. Ceram. Soc. 10 (5) (Jan. 1992) 347–367. J. Crank, the Mathematics of Diffusion, Second Edi, Clarendon Press, Oxford, 1975. D.S. Goldam, P.K. Gupta, Diffusion-Controlled Redox Kinetics in a Glassmelt, J. Am. Ceram. Soc. 66 (3) (1983) 188–190. M. Munoz, H. Bureau, V. Malavergne, B. Ménez, M. Wilke, C. Schmidt, A. Simionovici, A. Somogyi, F. Farges, In situ speciation of nickel in hydrous melts exposed to extreme conditions, Phys. Scr. T115 (2005) 921–922. A. Jambon, M.P. Semet, Lithium diffusion in silicate glasses of albite, orthoclase, and obsidian composition: an ion-microprobe determination, Earth Planet. Sci. Lett. 37 (3) (1978) 445–450.

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