Comunicação apresentada em: EMAS 2013 : 13th European 
Workshop on Modern Developments and Applications in Microbeam Analysis, Centro de Congressos da Alfândega do Porto, Portugal, 12 to 16 May 2013A sample of cryolite was studied with a JEOL JXA 8500-F electron microprobe under several operating conditions. A TAP crystal was used to analyse Na and Al 
and a LDE1 crystal to analyse F. As F and Na are both highly "volatile" elements, special care must be taken during analysis. The measurement order of Na, F 
and Al is not irrelevant and optimum conditions may also result in different combinations of accelerating voltage, beam current, beam size or counting times. 
Relevant X-ray signals were recorded in order to investigate the behaviour of the Na Ka and F Ka counts with elapsed time. The incident beam current was 
also recorded at the same time. In a clear contrast to what has normally been reported in the EPMA analysis of aluminosilicates and silicate glasses, we found 
that the Na X-ray counts increase with time. This increment of X-rays intensities for sodium in cryolite depends on the operating conditions and is 
accompanied by a strong migration of fluorine from the beam excitation volume, leading to a decrease in F X-ray counting rates. It was also observed that 
higher incident beam currents induce higher radiation damage in the mineral. The current instability is consistent with possible electron induced dissociation in 
the cryolite structure. An analytical protocol was achieved for 6 kV and 15kV accelerating voltage for the correct EPMA analysis of cryolite

Ferreira, Jorge Amaral

Guimarães, Fernanda

Piedade, A. P.

Silva, Paulo Bravo

Vieira, M. T. F.

IOP Conference Series : Materials Science and Engineering

Repositório do LNEG

MORPHOLOGICAL AND COMPOSITIONAL FEATURESOF PORTUGUESE POLYCRROME GLAZED POTTERYINVESTIGATED BY SEMIEDS - HINTS ABOUT THEMANUFACTURING PROCESSESA. Guilherme’, 5. Benemann2, V.-D. Hodoroaba2, J.Coroado3 andM.L. de Carvalho’1 University of Lisbon, Atomic Physics CentrePT- 1649-003 Lisbon, Portugal2 BAM Federal Institute for Materiais Research and Testing, Division 6.8:Surface Analysis and Interfacial ChemistryUnter den Eichen 87, DE-12205 Berlin, Germany3 Polytechnic Institute of Tomar, Dept. Arts, Conservation & RestorationPT-2300-3 13 Tomar, PortugalThis study addresses to the morphologicai and compositionai features of polychrome glazedceramic samples from Portugal by means of a SEMJEDS system (scanning electronmicroscopy energy-dispersive X-ray spectroscopy).Samples produced in the main pottery-making centres between the 1 6~ and 18t1i centuries(Lisbon and Coimbra) were the object of study. The main question to be answered is whetherthere are differences or not in the manufacturing procedures empioyed. For this purpose, twotypes ofsamples were analyzed: faiences and wall-tiles (the famous “azulejos”, in Portuguese).They ali have a ceramie body, a “base” glaze and a surface decoration. The anaiyses wereperformed on the glaze and on every coloured part of the samples. At first approach, the dataobtained by SEMJEDS have revealed to be of great usefiulness to identify heterogeneities onthe samples’ main parts.As a general feature of the glazes, the data reveal the permanent presence of elements such asSi, Pb, Sn, Ca and K. Si is the network forming agent and Pb and K have a network-modifier(fuser) character in the glassy matrix, in order to lower the meiting point of the Si-structure.Other fusers, such as Na and Mg have revealed to be key elements for tracing differences in themanufacturing processes. Sn is found in these samples as an opacifier, which makes the glazemat and allows a better application of surface decorations. By careful analysis of the SEMmicrographs, one sees that the Sn crystals (cassiterite Sn02) are mostly dispersed in deeperlayers ofthe glaze.As for the yellow pigment, Sb is the colour-carrier element and its crystals have typically ahexagonal shape, which is an indicative of the firing temperature used. The crystal size is inthe order of 2 j.tm and even smaller in some cases. Considering the other pigments (green,blue and purple), even with a high magnification, the pigment crystals seem to be very tiny(nm range) and well dispersed within the base glaze.ELECTRON MICROPROBE ANALYSIS OF CRYOLITEF. Guimarães’, P.J.A. Bravo A. Silva’, J. Ferreira’, A.P. Piedade2 andM.T.F. Vieira21 LNEG - National Laboratory of Energy and Geology, I.P., LaboratórioCiência e Tecnologia MineralRua da Amieira, P.O. Box 1089, PT-4466-901 San Mamede de Infesta,Portugal2 Universidade de Coimbra - Polo 11, Fac. Ciências e Tecnologia, Depto.Engenharia Mecânica, GNM-CEMUCRua Silvio Lima, PT-3030-790 Coimbra, Portugal _____________________Cryolite (Na3A1F6) is an uncommon aluminofluoride, with a chemical composition extremelyrich in fluorine and sodium (F: 53 - 54 %; Na: 32 - 34 %). Historically, natural cryolite hasbeen used as an aluminium ore and, more recently, as a solvent for bauxite in the electrolyticrefining of aluminium and also as a pesticide. Natural cryolite was only extracted in largequantities from a world-class deposit within a granite stock in Ivigtut, Greenland. Afier theexhaustion of Ivigtut deposit, another outstanding deposit of cryolite was found in the Pitingamining district, Brazil. Minor occurrences of cryolite and other aluminofluorides occur aroundthe world, but its rarity precludes their economic application. The unavailability of naturalcryolite in economic quantities led to the production of synthetic cryolite, which is wideiy usedin the electrolytic processing of alumina.References to electron microprobe analysis of aluminofluorides in the literature are vague andthe authors did not find any published quantitative analysis of cryolite by WDS. A sample ofcryolite from the Academia das Ciências de Lisboa Museum was studied with a JEOLJXA 8500-F electron microprobe under several operating conditions. A TAP crystal was usedto analyze Na and AI and a LDE1 crystal to analyse fluorine.As F and Na are both highly volatile elements, care must be taken during analysis. Themeasurement order of Na, F and Ai is not irrelevant and optimum conditions may also result indifferent combinations ofbeam current, spot size or counting times.Some X-ray signals were recorded in order to investigate the behaviour of the Na Ka and F KctX-ray counts with the elapsed time. The incident beam current was also recorded at the sarnetime. In a clear contrast to what happens in the EPMA analysis of aluminosilicates and silicateglasses we found that Na X-ray counts increase with time. This grow-in of X-rays intensitiesfor sodium in cryolite depends on the operating conditions and is accompanied by a strongmigration of fluorine from the beam excitation volume, leading to a decrease in F X-raycounting rates. It was also observed that higher incident beam currents induce higher radiationdamage in the mineral. The current instability is consistent with possible electron induceddissociation in the cryolite structure.An analytical protocol was achieved for 15 kV accelerating potential and several incident beamcurrents.

Electron microprobe analysis of cryolite

      Electron microprobe analysis of cryolite F Guimarães1,3, P Bravo Silva1, J Ferreira1, A P Piedade2 and M T F Vieira2   1 LNEG – National Laboratory of Energy and Geology, Rua da Amieira, Ap. 1089, 4466-901 S. Mamede de Infesta, Portugal 2 University of Coimbra, Faculty of Sciences and Technology, Department of Mechanical Engineering, Rua Silvio Lima, 3030-790 Coimbra, Portugal  E-mail: fernanda.guimaraes@lneg.pt  Abstract. A sample of cryolite was studied with a JEOL JXA 8500-F electron microprobe under several operating conditions. A TAP crystal was used to analyse Na and Al and a LDE1 crystal to analyse F. As F and Na are both highly volatile elements, special care must be taken during analysis. The measurement order of Na, F and Al is not irrelevant and optimum conditions may also result in different combinations of accelerating voltage, beam current, beam size or counting times. Some X-Ray signals were recorded in order to investigate the behaviour of the Na Kα and F Kα X-ray counts with the elapsed time. The incident beam current was also recorded at the same time. In a clear contrast to what happens in the EPMA analysis of aluminosilicates and silicate glasses, we found that Na X-ray counts increase with time. This grow-in of X-rays intensities for sodium in cryolite depends on the operating conditions and is accompanied by a strong migration of fluorine from the beam excitation volume, leading to a decrease in F X-ray counting rates.  It was also observed that higher incident beam currents induce higher radiation damage in the mineral. The current instability is consistent with possible electron induced dissociation in the cryolite structure. An analytical protocol was achieved for 6 kV and 15kV accelerating voltage. 1. Introduction Cryolite (Na3AlF6) is an uncommon mineral, although it is the most frequent aluminofluoride in nature [1]. Its chemical composition is extremely rich in fluorine and sodium (F: 53-54%, Na: 32-34%). Historically, natural cryolite has been used as an aluminium ore and, more recently, as a solvent for bauxite in the electrolytic refining of aluminium, and also as a pesticide. Natural cryolite was only extracted in large quantities from a world-class deposit within a granite stock in Ivigtut, Greenland [1]. After the exhaustion of Ivigtut deposit, another outstanding deposit of cryolite was found in the Pitinga mining district, Brazil [2, 3]. Minor occurrences of cryolite and other aluminofluorides occur around the world, mostly in peralkaline granites and pegmatites, but its rarity precludes their economic application. The unavailability of natural cryolite in economic quantities led to the production of synthetic cryolite, which is widely used in the electrolytic processing of alumina. In the last few years, there has been a growing interest on cryolite as a preferred component for thermodynamic models of peralkaline granitic and rhyolitic systems [4, 5, 6]. References to electron microprobe WDS analysis of aluminofluorides are rare in the literature, as accurate fluorine determination is still a difficult task, especially in F-rich minerals. In the case of                                                    3 To whom any correspondence should be addressed.       cryolite, this analytical problem gets worse due to the coexistence of two highly volatile elements, (F and Na). In this study, several WDS analyses on a cryolite sample from the Academia das Ciências de Lisboa Museum were performed under different operating conditions. Some X-Ray count rates were recorded in order to investigate the behaviour of the Na Kα and F Kα X-ray counts with the elapsed time. The incident beam current was also recorded at the same time in cryolite, and also in the calibrating standards used for Na (albite) and F (fluorite). The measurement order of the elements Na, F and Al was also taken into account. Both sequences F-Na-Al and Na-F-Al were used for analyses. In order to determine the effect of temperature on cryolite structure, some heating tests followed by XRD spectra acquisition were performed at the Faculty of Sciences and Technology of Coimbra on another cryolite sample.  2. Analytical Methods The EPMA analyses were performed with a JEOL JXA 8500-F electron microprobe, at LNEG, under several operating conditions. The following standards were used for all the quantitative determinations: fluorite (F Kα), albite (Na Kα) and orthoclase (Al Kα). Only one WDS spectrometer was used, equipped with a TAP crystal to analyze Na and Al and a LDE1 crystal was used to analyze F. All elements were analysed with 20 s counting times. The XRD spectra were obtained using a Philips X’Pert, at 40 kV and 35 mA, with Co radiation (λα1=0.178896 nm and λα2=0.179285 nm), equipped with collimator and Bragg–Brentano geometry, at University of Coimbra. A cryolite was heated from room temperature to 300ºC, at 5ºC·min-1 and 150 mbar against a blank of pure alumina with equivalent weight. All the tests were performed with a step size of 0.025º and a time per step of 0.5 s, in 20–80º range. The heating was performed at 5ºC·min-1 and after a 5 minute wait at each of the pre-defined temperature the spectra collection begun. The temperatures were: room temperature (RT), 60ºC, 100ºC, 205ºC, 300ºC and room temperature after cooling. The diffraction spectra were compared with ICDD (International Center for Diffraction Data) pattern nº82-0216, which corresponds to monoclinical cryolite.  3. Results Time-dependent X-rays intensity variation of Na Kα and F Kα in cryolite is presented in figure 1. The shaded areas show the 10s intervals of F and Na peak measurements during cryolite analysis.  At 15 kV and 1 nA, F and Na counts/s (cps) have opposite behaviours. In general, there’s a decrease of F cps and an increase of Na cps with time (figure 1a, b). Furthermore, the slopes of F count rates decrease and Na count rates increase are higher for a beam diameter of 5 µm. However, in the first 10 s an increase on F count rates was recorded before its drop off (figure 1a). The same phenomenon of F decrease and Na grow-in was observed at higher current beam (10 nA), but, for larger beam diameters, there was an increase in the F cps (figure 1c). When using a lower accelerating voltage (6kV), again the F count rate decreases with time as opposed to the increase of Na count rate, although the slopes of these variations are smaller (figure 2). At this accelerating voltage, when Na is the second element to be analysed and the beam diameter is 5 µm, the Na Kα intensity is too high and leads to a excessive Na weight % concentration (table 1). The grow-in of X-ray intensities for sodium (Na) in cryolite depends on the operating conditions and is accompanied by a strong migration of fluorine (F) from the beam excitation volume, leading to a decrease in F X-ray counting rates (figures 1, 2). This phenomenon is a clear contrast to what happens during EPMA analysis of aluminosilicates, feldspars and silicate glasses, where there is a decrease in Na Kα intensities, as Na+ ions move away from the bombarded area [7, 8]. A comparison between F and Na X-rays intensities variation has been made for cryolite, and for the calibrating standards fluorite and albite (figure 3). As can be observed, there is always a decrease in the number of X-rays counts, when compared to their initial values, except for Na Kα counts on cryolite. For the same time interval (160 s), F Kα dropped about 16 % in cryolite and only 6 % in fluorite. The Na Kα count rates increased about 9 % in cryolite and decreased 6 % in albite (figure 3).         Figure 1. Plots showing the F (a, c) and Na (b, d) count rates in cryolite versus beam exposure time, with 15 kV accelerating voltage and a beam current of 1 nA (a, b) and 10 nA (c, d). Each point represents the average of the number of X-rays obtained in 10 readings in a 5 s interval, starting from t=2.08 s. The shaded areas represent the time intervals of F and Na X-rays peak measurements during cryolite analysis. All elements were analysed with 20 s counting times.   Figure 2. Plots showing the F (a) and Na (b) count rates in cryolite versus beam exposure time, with 6 kV accelerating voltage and a beam current of 1 nA. Each point represents the average of the number of X-rays obtained in 10 readings in a 5 s interval, starting from t=2.5 s. The shaded areas represent the time intervals of F and Na X-rays peak measurements. All elements were analysed with 20 s counting times.        Figure 3. F (a) and Na (b) count rates variation with time in cryolite, fluorite (F) and albite (Na), at 15 kV, 10 nA and 10 µm beam diameter. Each point represents the average of the number of X-rays obtained in 10 readings in a 5 s interval, starting from t=2.08 s. Note that the decrease in F Kα intensities is accompanied by an increase in Na Kα count rates during time, and neither of these situations occur in fluorite or albite at the same operating conditions.   Some secondary electron images (SEI) and electron backscattered images (COMP) were taken at the end of three WDS quantitative analysis on cryolite, all at 15kV and 3 different probe currents: 0.5nA, 1nA and 10nA. It is evident the surface damage induced by the electron beam on cryolite, and, as it would be expected, higher incident beam currents induce higher radiation damage in the mineral surface (figure 4).     Figure 4. Secondary electron images (SEI) and backscattered electron images (COMP) of cryolite after EPMA analyses with 20 s counting times for each element. Only one WDS spectrometer was used to analyse the 3 elements (F, Na and Al).        In addition to the damage of the mineral surface, one could also register fluctuations on probe current with the elapsed time (figure 5).  For 15kV, 1 nA and Ø=10µm, probe current decreases drastically after about 105s for cryolite and remains relatively unchanged for albite and fluorite.   Figure 5. Fluctuations of probe current (set at 1 nA) versus time, in albite, fluorite and cryolite, with 15 kV and a 10 µm beam diameter. Current probe decreases drastically after about 105 s exposure time in cryolite.    Being cryolite a low thermal conductivity material, it is expected that a considerable local rise in temperature may occur, induced by the electron beam [8].  In order to investigate the influence of temperature rise in the cryolite structure, several heating tests followed by XRD spectra acquisition were performed. The results obtained showed that heating a cryolite sample until 300ºC does not change the structure of the mineral (figure 6).  Therefore, the observed cryolite surface damage may not be attributed to a temperature increase, but to the electron beam interaction with the structural lattice.  Figure 6. Some XRD spectra obtained during heating of a cryolite sample, showing that from room temperature (RT) to 300º C there is no structural dissociation of cryolite.   Table 1 presents some results of WDS analysis on cryolite performed with only 1 spectrometer for 2 values of accelerating voltage: 15 kV and 6 kV, 2 sequences of analysis (F-Na-Al and Na-F-Al) and several incident beam currents and beam diameters. Some WDS analysis were also performed scanning the beam in a raster (15kV, 1 nA) for the sequence of analyse Na-F-Al, but the results were       unacceptable for fluorine (F= 57,69% average of 4 analysis), although not so bad for the determination of sodium (Na =31.38%).  Table 1. Electron microprobe analysis of cryolite (wt. %), under different operating conditions. Accelerating voltage 15 kV Sequence of analysis F – Na – Al Na – F – Al Probe current (nA) 0.5 nA 1 nA 5 nA 10 nA 0.5 nA 1 nA 5 nA 10 nA Beam size (µm) 2 µm 5 µm 12 µm 20 µm 2 µm 5 µm 12 µm 20 µm F 57.70 58.38 58.05 57.68 54.18 55.02 53.85 56.78 Na 37.25 34.47 34.54 32.86 31.22 32.04 31.68 32.09 Al 13.35 13.66 14.14 12.78 14.03 13.31 13.94 13.01 Total 108.30 106.51 106.73 103.32 99.43 100.37 99.47 101.88 n 6 2 4 6 4 6 9 12          Accelerating voltage 6 kV     Sequence of analysis F – Na – Al Na – F – Al  Pure cryolite a  Probe current (nA) 1 nA 1 nA 1 nA 1 nA  Beam size (µm) 5 µm 12 µm 5 µm 12 µm  F 55.06 57.76 40.68 54.67  F 54.29  Na 43.66 32.36 40.42 31.47  Na 32.86  Al 15.20 13.72 15.23 13.70  Al 12.85  Total 113.92 103.84 96.33 99.84  Total 100.00  n 5 5 4 5    a Palache et al. [6]; n – number of analysis.  Values shown in bold are in good agreement with the ideal cryolite composition.   4. Conclusions Cryolite is highly sensitive to electron beam radiation even with a defocused beam. The problem rises with the increase of beam current. Cryolite damage observed under the electron bombardment may occur sooner (higher currents), or later (lower currents). The high drop of probe current (figure 5) is an indication of a clear damage in the structure. As has been demonstrated by [10] an electron beam induced dissociation occurs on cryolite. They proved to exist fluorine loss from the electron bombarded cryolite, due to the emission of fluorine atoms and, simultaneously, diffusion of fluorine ions into the area depleted by electron bombardment. However, no desorbed F was observed when heating the sample at ≈200 ºC. This electron induced dissociation of cryolite also occured under the operating conditions used in this study. The balance between desorbed F atoms and adsorbed F- ions may explain the difficulties in the analysis of F.   Heating tests followed by XRD spectra acquisition showed that heating a cryolite sample until 300ºC does not change the structure of the mineral (figure 6).  Therefore, the observed cryolite surface damage may not be attributed to a temperature increase, but to the electron beam interaction with the structural lattice.  Despite these problems, it is possible to perform quantitative EPMA analysis of cryolite, using only one WDS spectrometer, providing that:   - short counting times are used;  - Na must be the first element in the sequence of analyse;  - F is the second element in the sequence of analyse;  - a low probe current is used;  - the beam must be defocused within a limited range.         References [1] Bailey J 1980 The formation of cryolite and other aluminofluorides: a petrologic review Bull. Geol. Soc. Denmark 29 1–45 [2]  Bastos Neto A C, Pereira, V P, Ronchi L H, Lima, E F and Frantz J C 2009 The world-class Sn, Nb, Ta, F (Y, REE, Li) deposit and the massive cryolite associated with the albite-enriched facies of the Madeira A-type granite, Pitinga mining district, Amazonas state, Brazil Can. Mineral. 47 1329–57 [3] Costi H T, Dall’Agnol R, Pichavant M and Rämö O T 2009 The peralkaline tin-mineralized Madeira cryolite albite-rich granite of Pitinga, Amazonian craton, Brazil: petrography, mineralogy and crystallization processes Can. Mineral. 47 1301–27 [4] Dolejš D and Baker D R 2005 Thermodynamic modeling of melts in the system Na2O-NaAlO2-SiO2-F2O-1 Geochim. Cosmochim. Acta 69 5537–56 [5] Dolejš D and Baker D R 2006 Phase transitions and volumetric properties of cryolite, Na3AlF6: Differential thermal analysis to 100 Mpa Am. Mineral. 91 97–103 [6] Dolejš D and Baker D R 2007 Liquidus equilibria in the system K2O–Na2O–Al2O3–SiO2–F2O-1–H2O to 100 Mpa: I. Silicate–Fluoride Liquid Immiscibility in Anhydrous Systems J. Petrol. 48 785–806 [7] Morgan VI G B and London D 1996 Optimizing the electron microprobe analysis of hydrous alkali aluminosilicate glasses Am. Mineral. 81 1176–85 [8]  Reed S J B 2005 Electron Microprobe Analysis and Scanning Electron Microscopy in Geology (Cambridge: Cambridge University Press) [9] Palache C, Berman H and Frondel C 1951 The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana 7th Edition vol II (New York: John Wiley & Sons) pp 110–3  [10] Knapp A G and Hughes J R 1981 The kinetics of dissociation of Cryolite (Na3AlF6) induced by electron bombardment J. Appl. Phys. 52 438–42     

      Electron microprobe analysis of cryolite F Guimarães1, P Bravo Silva1, J Ferreira1, A P Piedade2 and M T F Vieira2 1 LNEG - National Laboratory of Energy and Geology, Rua da Amieira, Ap. 1089, PT-4466-901 S. Mamede de Infesta, Portugal 2 University of Coimbra, Faculty of Sciences and Technology, Department of Mechanical Engineering, Rua Silvio Lima, PT-3030-790 Coimbra, Portugal E-mail: fernanda.guimaraes@lneg.pt Abstract.  A sample of cryolite was studied with a JEOL JXA 8500-F electron microprobe under several operating conditions.  A TAP crystal was used to analyse Na and Al and a LDE1 crystal to analyse F.  As F and Na are both highly “volatile” elements, special care must be taken during analysis.  The measurement order of Na, F and Al is not irrelevant and optimum conditions may also result in different combinations of accelerating voltage, beam current, beam size or counting times.  Relevant X-ray signals were recorded in order to investigate the behaviour of the Na Kα and F Kα counts with elapsed time.  The incident beam current was also recorded at the same time.  In a clear contrast to what has normally been reported in the EPMA analysis of aluminosilicates and silicate glasses, we found that the Na X-ray counts increase with time.  This increment of X-rays intensities for sodium in cryolite depends on the operating conditions and is accompanied by a strong migration of fluorine from the beam excitation volume, leading to a decrease in F X-ray counting rates.  It was also observed that higher incident beam currents induce higher radiation damage in the mineral.  The current instability is consistent with possible electron induced dissociation in the cryolite structure.  An analytical protocol was achieved for 6 kV and 15kV accelerating voltage for the correct EPMA analysis of cryolite. 1. Introduction Cryolite (Na3AlF6) is an uncommon mineral, although it is the most frequent aluminofluoride in nature [1].  Its chemical composition is extremely rich in fluorine and sodium (F: 53 – 54 %;  Na: 32 – 34 %).  Historically, natural cryolite has been used as an aluminium ore and, more recently, as a solvent for bauxite in the electrolytic refining of aluminium, and also as a pesticide.  Natural cryolite was only extracted in large quantities from a world-class deposit within a granite stock in Ivigtut, Greenland [1].  After the exhaustion of the Ivigtut deposit, another outstanding deposit of cryolite was found in the Pitinga mining district, Brazil [2, 3].  Minor occurrences of cryolite and other aluminofluorides occur around the world, mostly in peralkaline granites and pegmatites, but its rarity precludes their economic application.  The unavailability of natural cryolite in economic quantities led to the production of synthetic cryolite, which is widely used in the electrolytic processing of alumina.  In the last few years, there has been a growing interest on cryolite as a preferred component for thermodynamic models of peralkaline granitic and rhyolitic systems [4-6]. References to electron microprobe WDS analysis of aluminofluorides are rare in the literature, as accurate fluorine determination is still a difficult task, especially in F-rich minerals.  In the case of cryolite, this analytical problem gets worse due to the coexistence of two highly “volatile” elements, EMAS 2013 Workshop IOP PublishingIOP Conf. Series: Materials Science and Engineering 55 (2014) 012006 doi:10.1088/1757-899X/55/1/012006Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distributionof this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.Published under licence by IOP Publishing Ltd 1

Guimarães, Fernanda M. G.

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Electron microprobe analysis of cryolite

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