Encyclopedia of Glass Science, Technology, History, and Culture. Группа авторов

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Usually <10 keV 2.4 × 10¹³–3.4 × 10¹⁷ ~1–1000 nm Energy loss of inelastically scattered X‐ray photons In‐situ high‐pressure energy loss spectra of low z elements (equivalent to XANES), short‐range structure, electronic structure XPS ~0.1–1400 eV 2.4 × 10¹³–3.4 × 10¹⁷ ~1–3000 nm Energy of ejected core and valence electrons Oxygen speciation (BO, NBO, free oxygen) EELS/ELNES 10 meV–10 keV 7.2 × 10¹¹–2.9 × 10¹⁷ ~1–1000 nm Energy loss of transmitted electrons through the sample Same as XANES IR 886 meV–3eV 430 × 10¹²–300 × 10⁹ 1 mm–2500 nm Molecular vibrations Vibrational states, quantification of CO₂/H₂O in glasses, coordination states, short‐ and intermediate‐range structure Raman 1.2–120 meV 3 × 10¹¹–1.5 × 10¹⁴ 0.5 mm–1000 nm Molecular vibrations, inelastic photon interactions Vibrational states, Q species, ring statistics, short‐ and intermediate‐range structure Brillouin 1.2 × 10⁻³–7.4 × 10⁻⁴ eV 10⁷–1.8 × 10¹¹ 100–1000 nm Inelastic photon–phonon interactions Elastic and acoustic properties UV/Vis 1.7–124 eV 30 × 10¹⁹–790 × 10¹² 10–700 nm Valence electron transitions Oxidation and coordination states of transition metals NMR 12.4 peV–1.24 meV 3 × 10³–300 × 10⁹ ~1 km–1 mm Nuclear spin interactions Short‐ and intermediate‐range structure, bond angles, coordination states, Q species, dynamics Mössbauer 100 keV >10¹⁹ <0.1 nm Nuclear transitions Oxidation state and coordination of Mössbauer active nuclei: typical Fe, Sn in glasses

In order to select the most suitable technique for probing the glass of interest, one has to determine what aspect of the structure is to be probed (bulk or atom specific), and what is the length scale to be probed (short‐range, intermediate‐range, or extended‐range)? In many instances more than one technique will need to be employed. I will briefly discuss a number of common and not so common techniques for deriving structural information on glasses. Whereas space constraints limit the detail that can be provided, I will provide a general overview of what aspect of the structure is probed and what information can be determined from each method. The reader should refer to any of a number of detailed reviews of the specific techniques currently available (e.g. [1, 2]).

      Acronyms

      3Qtriple quantumAFMatomic force microscopyAWAXSanomalous wide angle X‐ray scatteringBEbinding energyBObridging oxygenCNcoordination numberDAXSdiffraction anomalous X‐ray scatteringEELSelectron energy‐loss spectroscopyELNESenergy loss near‐edge spectroscopyeVelectron voltEXAFSextended X‐ray absorption fine structureFIDfree induction decayFSDPfirst sharp diffraction peakFT‐IRFourier transform infraredFWHMfull width at half maximumHRTEMhigh‐resolution transmission electron microscopyIRinfraredIROintermediate‐range orderISisomer shiftIVCTintervalence charge transferkeVkilo electron voltKKKramers–KrönigLOlongitudinal opticLROlong‐range orderMASmagic angle spinningMDmolecular dynamicsMQmultiple quantumNBOnon‐bridging oxygenNMRnuclear magnetic resonanceNRIXSnon‐resonant inelastic X‐ray scatteringPDFpair distribution functionPSFpartial structure factorQSquadrupole splittingRDFradial distribution functionRFradio frequencyRMCreverse Monte CarloSROshort‐range orderTOtransverse opticTSFtotal structure factorUVultra violetVisvisibleXANESX‐ray absorption near‐edge structureXASX‐ray absorption spectroscopyXPSX‐ray photoelectron spectroscopyXRSX‐ray Raman spectroscopy

2 Diffraction (Scattering)

      2.1 X‐ray and Neutron

      Neutron and X‐ray diffraction are two of the principal techniques used to probe the bulk structure of glasses through determination of average bond lengths, coordination numbers (CN), and angles over both the short (nearest neighbors) and intermediate (next‐nearest neighbors) length scales. Data analysis and interpretation are comparable for X‐ray and neutron diffraction so that I will differentiate between the two methods only when needed. In passing, note that in earlier studies the interaction between the X‐rays and the sample was termed scattering, and not diffraction as made now.

      For X‐rays, diffraction experiments are readily made but they are not well suited to discriminate between neighbor atoms in the periodic table, such as silicon and aluminum, because of the similar electronic clouds with which X‐rays interact in these cases. Thanks to their lack of electrical charge, neutrons are (with neutrinos) the only particles that can penetrate a condensed phase. They do not interact with electronic clouds, but are diffracted by atomic nuclei because they are strongly sensitive to nuclear forces. If both methods are available, the choice of X‐ray or neutron diffraction depends to some extent on the chemical composition of the glass. Neutrons are, for instance, better suited than X‐rays for investigating light elements such as H and they have the advantage of providing better spatial resolution and allowing more detailed information to be obtained through isotope substitution methods, which rely on the fact that neutron diffraction is sensitive to the neutron content of a nuclei. Practical factors have also to be taken into account: intense sources are much more widely available for X‐rays than for neutrons, whereas the required sample sizes are of the order of 1 mg and 50 g, respectively. The samples themselves may be in the form of powders, glass chips, or shaped glass chips.

The “diffraction pattern” of a glass is very different from that of a crystal (cf. [3]). A crystal will produce a series of “spots” or “reflections” on a two‐dimensional diffraction image or sharp diffraction lines on a powder diffraction trace. These cannot be seen in the diffraction image of a glass. This contrast is illustrated by the area electron‐diffraction images of a crystalline material (Ba₂TiGe₂O₈, Ge‐substituted fresnoite) and of an amorphous material (Ba₂TiSi₂O₈, fresnoite glass) shown in Figure 1a, b. Clearly, no “reflections” are observed in the glass

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