Transition and post-transition metal ions in borate glasses: Borate ligand speciation, cluster formation, and their effect on glass transition and mechanical properties

Abstract

A series of transition and post-transition metal ion (Mn, Cu, Zn, Pb, Bi) binary borate glasses was studied with special consideration of the cations impact on the borate structure, the cations cross-linking capacity, and more generally, structure-property correlations. Infrared (IR) and Raman spectroscopies were used for the structural characterization. These complementary techniques are sensitive to the short-range order as in the differentiation of tetrahedral and trigonal borate units or regarding the number of non-bridging oxygen ions per unit. Moreover, vibrational spectroscopy is also sensitive to the intermediate-range order and to the presence of superstructural units, such as rings and chains, or the combination of rings. In order to clarify band assignments for the various borate entities, examples are given from pure vitreous BO to meta-, pyro-, ortho-, and even overmodified borate glass compositions. For binary metaborate glasses, the impact of the modifier cation on the borate speciation is shown. High field strength cations such as Zn enhance the disproportionation of metaborate to polyborate and pyroborate units. Pb and Bi induce cluster formation, resulting in PbO- and BiO-pseudophases. Both lead and bismuth borate glasses show also a tendency to stabilize very large superstructural units in the form of diborate polyanions. Far-IR spectra reflect on the bonding states of modifier cations in glasses. The frequency of the measured cation-site vibration band was used to obtain the average force constant for the metal-oxygen bonding, F. A linear correlation between glass transition temperature (T) and F was shown for the metaborate glass series. The mechanical properties of the glasses also correlate with the force constant F, though for cations of similar force constant the fraction of tetrahedral borate units (N) strongly affects the thermal and mechanical properties. For paramagnetic Cu- and Mn-borate glasses, N was determined from the IR spectra after deducing the relative absorption coefficient of boron tetrahedral versus boron trigonal units, α = α/α, using NMR literature data of the diamagnetic glasses.

Influence of Cooling Rate on Cracking and Plastic Deformation during Impact and Indentation of Borosilicate Glasses

“…An echometer (model 1077, Karl Deutsch GmbH) working with an accuracy of ±1 ns was employed. More information on ultrasonic measurements and how elastic properties such as shear modulus G, bulk modulus K, and Young's modulus E, and Poisson ratio ν can be found elsewhere (Limbach et al 2015;Möncke et al, 2016).…”

“…In general, both processes, densification and shear flow are sensitive toward changes in strain rate (Shikimaka et al, 2016); the contribution of each, however, depends on composition, atomic packing density, and network connectivity (Yoshida et al, 2005;Limbach et al, 2014;Möncke et al, 2016). Shikimaka et al (2016) concluded densification to be triggered by shear and pressure.…”

Spectroscopic investigation of samarium‐doped lead oxyflouroborate glasses using photo and cathode luminescence

“…Lead borate glasses have shown to exhibit a large glass forming region . Because of the large difference between the masses of lead and boron atoms are vibrational modes of PbO polyhedral and the borate network well separated in the IR and Raman spectra . Lead borate glasses have been used successfully as efficient laser host material .…”

Tb3+as probe ion—Clustering and phase separation in borate and borosilicate glasses

“…The structure of the un‐doped ZnB glass mainly consists of boroxol and borate rings. ZnO cause a partial disproportionation of the (BØ 2 O) − and (BØ 4 ) − groups to (BØO 2 ) 2− and BØ 3 groups . However, Zn 2+ with high field strength is not only a modifier ion.…”

“…The structure of most un‐doped borate and borosilicate glasses used for these investigations is relatively well understood and was studied before with different methods. Many papers were published by us and other authors . But unfortunately, it was not possible for us up to now, to determine the local structure of Tb 3+ , or other RE 3+ ions, in the selected borate and borosilicate glasses in more detail.…”