Anomalous Deformation Behavior in ULE Glass upon Microindentation: A Vibrational Spectroscopic Investigation in the Induced Structural Changes of a Ti-Silicate Glass

Abstract

Ultralow expansion (ULE) glass, a binary TiO2–SiO2 glass with 5.67 mol % TiO2, was exposed to microindentation. Vitreous silica was similarly treated and used as a reference material, including the characterization of mechanical properties by means of ultrasonic echography and nanoindentation. The structural modifications induced by indentation were analyzed by micro-Raman spectroscopy. The observed structural changes are consistent with an anomalous, densification-driven, deformation mechanism similar to those observed for vitreous silica or commercially relevant low alkali borosilicate glasses like Duran. As for these fully polymerized glasses, the Raman spectra of indents in the ULE glass are characterized by an upshift of the 407 cm–1 band and an increase in the intensity of the D1 and D2 defect bands, all consistent with structural rearrangements from mostly larger five- and six-member rings to a larger population of smaller four- and three-member rings and an overall lowering of the free volume in the glass. However, contrary to silicon, titanium may change its coordination number under the impact of microindentation. Raman spectra of selected reference materials such as TiO2 and BaTiO3, with known octahedral titanium coordination and known connectivity, as well as fresnoite Ba2TiSi2O8 with known fivefold Ti4+ coordination, are therefore included in this study in support of assigning the new activity appearing in the Raman spectra after an indentation of the ULE glass sample.

The dual role of bismuth in Li2O–Bi2O3–B2O3 glasses along the orthoborate join

“…The Raman spectra of all bismuth containing glasses presented in Figure 9 are dominated by strong scattering below 700 cm −1 . This is understood by considering the large polarizability of Bi 3+ relative to B 3+ , similar to the situation of Ti 4+ in ultra‐low expansion (ULE) silica glasses 53 . As the polarizability of B 3+ is 0.003 Å 3 , the addition of just 10 mol% Bi 2 O 3 induces intense scattering arising from bismuthate species due to the high polarizability of Bi 3+ , which is 1.508 Å 3 54,55 .…”

“…This is understood by considering the large polarizability of Bi 3+ relative to B 3+ , similar to the situation of Ti 4+ in ultra-low expansion (ULE) silica glasses. 53 As the polarizability of B 3+ is 0.003 Å 3 , the addition of just 10 mol% Bi 2 O 3 induces intense scattering arising from bismuthate species due to the high polarizability of Bi 3+ , which is 1.508 Å 3 . 54,55 For relatively low bismuth oxide content, the spectra display a prominent maximum at 660 cm −1 accompanied by activity at 365 cm −1 and slightly above 426 cm −1 .…”

Microgravity effects on nonequilibrium melt processing of neodymium titanate: thermophysical properties, atomic structure, glass formation and crystallization

“…The prominent 738 cm −1 is consistent with the stretching activity of corner-sharing TiO 6 moieties 39 . The broadest peak, centered at 596 cm −1 , is most likely due to edge-sharing TiO 6 units and is just slightly below the 600–650 cm −1 range where the corresponding feature is found in anatase and rutile 39 , 42 . Finally, the peak at ~828 cm −1 is most likely due to TiO 5 polyhedra.…”

Second‐harmonic generation and structural rearrangements in multicomponent antimonite glasses by electrothermal poling

“…In‐line with this observation 23 is the band developing at 935 cm −1 in the IR spectra of glasses x Na 2 O–(1− x )SiO 2 with increasing Na 2 O content; this band dominates the x = 0.45 glass spectrum and was assigned to Si–O stretching in Q 2 silicate units with two bridging and two non‐bridging oxygen atoms 56 . The absence of a corresponding Si–O stretching impurity band in the Raman spectrum (Figure 4) can be explained by the low polarizability of Si 4+ ( α = 0.033 Å 3 ) compared to the much higher polarizability of Sb 3+ ( α = 1.111 Å 3 ), 57 noting that IR spectroscopy is not affected by this characteristic 58–60 …”

“…56 The absence of a corresponding Si-O stretching impurity band in the Raman spectrum (Figure 4) can be explained by the low polarizability of Si 4+ (α = 0.033 Å 3 ) compared to the much higher polarizability of Sb 3+ (α = 1.111 Å 3 ), 57 noting that IR spectroscopy is not affected by this characteristic. [58][59][60] The remaining bands below 800 cm −1 are assumedly related to antimonite polyhedra. The IR spectrum is dominated by a band at 606 cm −1 with a shoulder at ∼690 cm −1 .…”