Sound propagation has been investigated at megahertz and gigahertz frequencies in B2O3 solids which have been pressure quenched to go through different glassy phases having growing density until the crystalline state. Over the temperature range between 10 and 300 K, the attenuation and velocity of sound in glasses are regulated by classical activation over potential barriers of structural defects and vibrational anharmonicity. The defect states are absent in the crystalline phase whose acoustic behavior is determined only by the anharmonic coupling between sound waves and thermal vibrations. Our study leads to identification of the specific superstructural units subjected to thermally activated motions in vitreous B2O3. These molecular groups are the boroxol rings which are formed due to the poor atomic packing of glassy networks and are missing in the crystal.
Identification of relaxing structural defects in densifiedB2O3glasses
FIORETTO, Daniele;
2014
Abstract
Sound propagation has been investigated at megahertz and gigahertz frequencies in B2O3 solids which have been pressure quenched to go through different glassy phases having growing density until the crystalline state. Over the temperature range between 10 and 300 K, the attenuation and velocity of sound in glasses are regulated by classical activation over potential barriers of structural defects and vibrational anharmonicity. The defect states are absent in the crystalline phase whose acoustic behavior is determined only by the anharmonic coupling between sound waves and thermal vibrations. Our study leads to identification of the specific superstructural units subjected to thermally activated motions in vitreous B2O3. These molecular groups are the boroxol rings which are formed due to the poor atomic packing of glassy networks and are missing in the crystal.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
