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Journal Articles

Pressure-induced structural transformations and the anomalous behavior of the viscosity in network chalcogenide and oxide melts

Brazhkin, V. V.*; Katayama, Yoshinori; Kanzaki, Masami*; Kondrin, M. V.*; Lyapin, A. G.*

JETP Letters, 94(2), p.161 - 170, 2011/09

 Times Cited Count:11 Percentile:60.12(Physics, Multidisciplinary)

It is known that a number of compressed melts undergo structural phase transitions. Data on the structural changes at high pressures in chalcogenides (AsS, As$$_{2}$$S$$_{3}$$) and oxide (B$$_{2}$$O$$_{3}$$) melts with a network structure have been reviewed. Viscosity is one of the fundamental physical properties of a liquid. For various melts, it varies in a very wide range. Structural transformations in melts induce the corresponding changes in all physical properties, in particular viscosity. The measurements of the viscosity of a number of melts at high pressures and temperatures by the radiographic method have been reported. Changes in the viscosity by several orders of magnitude have been detected when the pressure is varied by several gigapascals. The diffusion mechanism in network structure melts at various pressures has been analyzed.

Journal Articles

Densified low-hygroscopic form of P$$_{2}$$O$$_{5}$$ glass

Brazhkin, V. V.*; Akola, J.*; Katayama, Yoshinori; Kohara, Shinji*; Kondrin, M. V.*; Lyapin, A. G.*; Lyapin, S. G.*; Tricot, G.*; Yagafarov, O.

Journal of Materials Chemistry, 21(28), p.10442 - 10447, 2011/07

 Times Cited Count:14 Percentile:44.78(Chemistry, Physical)

P$$_{2}$$O$$_{5}$$ compound is an archetypical glass-forming oxide with a high hygroscopicity. We found that the quenching from the P$$_{2}$$O$$_{5}$$melt under ultrahigh pressures enables obtaining densified P$$_{2}$$O$$_{5}$$ glasses with a residual densification up to 12% at normal conditions. These glasses have a low hygroscopicity and can exist under air conditions for several weeks. An examination of the structure of the new form of P$$_{2}$$O$$_{5}$$ glass reveals a cardinal decrease of the volume of nanovoids in the glassy matrix.

Journal Articles

Structural transformation yielding an unusual metallic state in liquid As$$_{2}$$S$$_{3}$$ under high pressure

Brazhkin, V. V.*; Katayama, Yoshinori; Kondrin, M. V.*; Lyapin, A. G.*; Saito, Hiroyuki

Physical Review B, 82(14), p.140202_1 - 140202_4, 2010/10

 Times Cited Count:14 Percentile:54.85(Materials Science, Multidisciplinary)

The As$$_{2}$$S$$_{3}$$ melt at room pressure represents a liquid having a three-dimensional network structure, semiconducting properties, and a huge viscosity. We have found that under high pressure a considerable change in the medium and short-range structure of this liquid is observed. Intermediate-range order correlations in the atomic arrangement almost disappear under pressure and an increase in the coordination number is observed.

Journal Articles

AsS melt under pressure; One substance, three liquids

Brazhkin, V. V.*; Katayama, Yoshinori; Kondrin, M. V.*; Hattori, Takanori; Lyapin, A. G.*; Saito, Hiroyuki

Physical Review Letters, 100(14), p.145701_1 - 145701_4, 2008/04

 Times Cited Count:41 Percentile:83.86(Physics, Multidisciplinary)

An ${it in situ}$ high-temperature high-pressure X-ray diffraction, resistivity measurements, and quenching from melt were performed on liquid chalcogenide AsS. The obtained data provide direct evidence for the existence three forms in the melt under compression: one is a moderate viscosity molecular liquid, the second one is a high-viscosity nonmetallic polymerized liquid and the third one is a low-viscosity metallic liquid. The two transformations occur at P $$sim$$ 1.6-2.2 GPa and at P $$sim$$ 4.6-4.8 GPa. Upon rapid cooling, molecular and metallic liquids crystallize to normal and high-pressure phases, respectively, while a polymerized liquid is easily quenched to a new AsS glass. General aspects of multiple phase transitions in liquid AsS, including relations to the phase diagram of the respective crystalline, are discussed.

Journal Articles

Structural transformations in liquid, crystalline, and glassy B$$_{2}$$O$$_{3}$$ under high pressure

Brazhkin, V. V.*; Katayama, Yoshinori; Inamura, Yasuhiro; Kondrin, M. V.*; Lyapin, A. G.*; Popova, S. V.*; Voloshin, R. N.*

JETP Letters, 78(6), p.393 - 397, 2003/06

 Times Cited Count:27 Percentile:76.4(Physics, Multidisciplinary)

We present in situ (X-ray diffraction) and ex situ (quenching) structural studies of crystalline, liquid, and glassy B$$_{2}$$O$$_{3}$$ up to 9 GPa and 1700 K, drawing equilibrium and nonequilibrium phase diagrams of B$$_{2}$$O$$_{3}$$, Particularly, we have determined the melting curve, the stability regions for crystalline B$$_{2}$$O$$_{3}$$ and B$$_{2}$$O$$_{3}$$ II modifications, the regions of transformations, such as densification or crystallization, for both the liquid and glassy states, including the region of sharp first-order-like transition in liquid B$$_{2}$$O$$_{3}$$ to a high-density phase near 7 GPa. Quenching experiments also show that the transition to the high-density liquid can occur at much lower pressures in nonstoichiometric melts with an excess of boron. B$$_{2}$$O$$_{3}$$ is the first glassformer whose transformations in the disordered state have been comparatively studied for both liquid and glassy phases.

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