Raman scattering as a probe of intermediate phases in glassy networks

Abstract

Bulk glass formation occurs over a very small part of phase space, and 'good' glasses (which form even at low quench rates ∼10 K/sec) select an even smaller part of that accessible phase space. An axiomatic theory provides the physical basis of glass formation, and identifies these sweet spots of glass formation with existence of rigid but stress-free networks for which experimental evidence is rapidly emerging. Recently, theory and experiment have come together to show that these sweet spots of glass formation occur over a range of chemical compositions identified as 'intermediate phases' (IPs). These ranges appear to be controlled by elements of local and medium-range molecular structures that form isostatically rigid networks. IP glasses possess nonhysteretic glass transitions (T g 's) that do not age much. Raman scattering has played a pivotal role in elucidating the molecular structure of glasses in general, and in identifying domains of IPs. Experiments reveal that these phases possess sharp phase boundaries and are characterized by an optical elasticity that varies with network mean coordination number, r, as power law. In this review, we provide examples in chalcogenide and oxide glass systems in which these phases along with optical elasticity power laws have been established. IP glasses represent self-organized nanostructured functional materials optimized by nature.

Network structure and thermal stability study of high temperature seal glass

“…[12][13][14] For chalcogenide glasses, Raman scattering played a pivotal role in elucidating the molecular structures and identifying domains of intermediate phases. 15 Raman spectra from Na 2 O -CaO-MgO-Al 2 O 3 -SiO 2 system were interpreted in terms of structural alteration as the composition was altered from the binary end members to more complicated glasses. 16 Addition of CaO and MgO to Na 2 O -SiO 2 glasses acted only to increase the disorder of the network slightly.…”

A Fast and Cost-Effective Detection of Melamine by Surface Enhanced Raman Spectroscopy Using a Novel Hydrogen Bonding-Assisted Supramolecular Matrix and Gold-Coated Magnetic Nanoparticles

“…A strong NdFeB cylinder magnet (10 mm in diameter, 3 mm in thickness, Jiangdong Magnetic Industry of Ningbo Co. Ltd., Ningbo, China) was placed under each slide to separate and concentrate the gold magnetic nanoparticles to a pellet point. The laser irradiation of the pellets produced Raman spectra of RhB and its characteristic peak at 1510 cm −1 was analyzed to build the calibration curve for melamine since the peaks between 1200 and 1400 cm −1 were prone to interference with the glass background of slides [47]. Each recorded Appl.…”

Recent advances in linear and nonlinear Raman spectroscopy II

“…A review of Raman scattering as a probe of the intermediate phases in glassy networks has been given by Boolchand et al 143 Theoretical, as well as experimental results, showed that glass formation occurs over a range of chemical compositions identified as 'intermediate phases'.…”