Use of Electron Paramagnetic Resonance for Investigating Glasses and Raw Materials (Review)

Abstract

It is shown that electron paramagnetic resonance can be used to study the fine structure of glasses and glass enamel materials as well as to find and identify defects in glass. The spectra of paramagnetic ions (Cu 2+ , V 4+ , Ti 3+ , Mo 5+ Mn 2+ , Fe 3+ ) are discussed. Specific examples of the detection of these ions in sitals, in which they are introduced as surface-active additives or are present as impurities entering the crystallized glass via the raw materials, are examined. It is determined that the most informative ions for studying the structure and phase separation of glass are Cu 2+ and V 4+ . Electron Paramagnetic ResonanceElectron paramagnetic resonance (EPR), discovered experimentally by E. K. Zavoiskii in 1944, is now widely used as a method of investigating different substances and processes in physics, chemistry, biology, geology, medicine, and other areas of science and technology. It should be noted that the EPR phenomenon has also been studied intensively from the theoretical and experimental standpoints. However, as a method of investigating substances or the processes occurring in them its importance is not diminishing but rather increasing because the range of new materials and their applications is expanding.EPR is a spectral method, based on resonance absorption of microwave electromagnetic radiation by paramagnetic particles, whose magnetic moments are tuned in resonance by applying a magnetic field.All substances contain electrons possessing orbital and spin magnetic moments, and one would think that EPR can be observed for all of them. However, the atoms and molecules comprising matter are constructed in such a manner that their filled electronic shells have a zero magnetic moment. EPR is observed only for 1) magnetic centers specially created by high-energy radiation (g-, x-rays, fast neutrons, ions of heavy particles, and others), 2) free radicals, and 3) atoms with initially unfilled inner electronic shells (transition elements (TE) with partially filled 3d-, 4d-, or 5d-shells, rare-earth elements with an unfilled 4f-shell and actinides with an unfilled 5f-shell). Such substances contain centers possessing constant magnetic moments, randomly oriented relative to one another in the absence of an external magnetic field. In accordance with Boltzmann's law most magnetic moments are oriented along the field.The energy of particles with a magnetic moment m directed parallel to an external magnetic field (lower energy level) is less than the energy of particles with m oriented opposite to the field (upper energy level). When a high-frequency electromagnetic field is applied absorption of electromagnetic energy equal to the energy difference DE between the upper and lower energy levels (in the case of a two-level system) occurs and is accompanied by re-orientation of the magnetic moment of the particle (resonance transition from the lower to the upper level). The resonance condition has the formwhere g is a spectroscopic splitting factor dependent on the nature of the magnetic moment and i...

Electron Spin Resonance Investigations on Perovskite Solar Cell Materials Deposited on Glass Substrate

“…These spectra exhibit a typical powder pattern, characterized by gx = gy = 4.2, gz = 9.3. Based on g-values reported in the literature works [18,19] together with our controlled measurements, we established that these signals originate from the glass substrate itself and not from the other layers. We assigned these spectra to an unexpected Fe 3+ (high-spin, S = 5/2, I = 0) ion, which is octahedrally (six-fold) coordinated with oxygen ions present in the glass substrate.…”

Magnetic Resonance and Conductivity Study of Lead–Cadmium Fluorosilicate Glasses and Glass-Ceramics

“…Recently, Bogomolova et al correlated the pair of Cu 2+ EPR parameters (g ∥ and A ∥ ) to the bonding nature of the Cu 2+ ions in some oxide glasses and showed that the parameters for each system of glasses are grouped in definite regions depending on the type of glass former (phosphate, borate, silicate, aluminum borate, etc). 46 The values obtained for our fluorosilicate glass, g ∥ = 2.365 and A ∥ = 140 × 10 −4 cm −1 , lie in the range assigned to Cu 2+ in silicate and lead silicate glasses (Figure 3 in ref 46). This result suggests that the covalency between the copper 3d orbital and the ligand orbitals of our fluorosilicate glass is similar to that found in the lead silicate glasses.…”

“…The value for our fluorosilicate glass, α 2 = 0.82, suggests a moderate covalency for the σ-bonding. A comparison of this α 2 value with that derived for Cu 2+ -doped fluorophosphate glasses (α 2 = 0.77–0.81) 43 , fluoroaluminate glasses (α 2 = 0.77), and lead silicate glasses (α 2 = 0.80) indicates the similarity of the copper covalencies of these strong ligand field copper systems. In addition, we verify that the exchange interaction between copper centers in the studied fluorosilicate glass is not significant.…”

Experimental methods in chemical engineering: Preface

“…BET, BJH gas V 70 45 400 TGA [31] Thermogravimetric Analysis T mass 65 10 400 FT-IR [32] Fourier Transform Infrared photons photons 62 25 000 (N)IR (Near)Infrared IR IR 61 77 000 MS Mass Spectroscopy molecules ions 50 62 000 TEM [33] Transmission Electron Microscopy e − e − 47 30 500 PSD [34] Particle Size Distribution photons photons 36 26 000 UPS Ultraviolet Photoelectron Spectroscopy UV e − 33 6700 UV-Vis [35] Ultraviolet- [36] Differential Scanning Calorimetry T H 21 11 900 ICP [37] Inductively Coupled Plasma, -MS ions ions 21 12 000 NMR [38] Nuclear Magnetic Resonance mgn fld radio 12 45 000 TPD Temperature Programmed Desorption T mass 12 2800 TPO Temperature Programmed Oxidation T mass 11 2000 XRF [39] X-Ray Fluorescence X-rays X-rays 11 4600 AES Auger Electron Spectroscopy X-rays e − 10 4100 Raman [40] Raman Spectroscopy photons photons 8 37 500 DRIFT Diffuse Reflectance IR Fourier Transform IR IR 6 900 ESR [41] Electron Spin Resonance, EPR photons photons 5 8500 AFM [42] Atomic Force Microscopy distance force 4 18 000 FEM [43] Field journals. A bibliometric map for each technique will give context to the work and identify what scientific disciplines use it.…”