X-ray induced temperature dependent amorphous-amorphous transitions in the GeO2 glass

Glasses are non-equilibrium materials whose structure and dynamics can be strongly modified by external perturbations such as ionizing radiation. This thesis investigates the effects of intense X-ray irradiation on vitreous germanium dioxide (v-GeO2), a prototypical strong oxide glass, by combining X-ray photon correlation spectroscopy (XPCS), X-ray diffraction (XRD), and inelastic X-ray scattering (IXS). The results demonstrate that intense X-rays induce atomic dynamics and structural transformations in v-GeO2 far below the glass transition temperature. The induced dynamics evolves with absorbed dose toward a stationary state whose properties depend on the irradiation temperature. Structural measurements reveal increased density fluctuations and reduced medium-range order, indicating a radiation-induced rejuvenation of the glass toward higher fictive-temperature states. To investigate these phenomena, novel XPCS data-analysis methodologies were developed, including the multi-tau two-time-correlation (MTTTC) approach and advanced detector corrections, enabling reliable measurements over extended timescales and low-signal conditions. Finally, the combination of XPCS and IXS measurements allows the non-ergodicity factor and density fluctuations to be studied across a broad frequency range, providing new insight into the microscopic mechanisms governing irradiation-induced amorphous-amorphous transitions in oxide glasses.

Grantor dc:publisher

Università degli studi di Trento

Year dc:date

2026

Author dc:creator

• Brugnara, Fabio

Contributors dc:contributor

• Zanatta, Marco
• Baldi, Giacomo

Statement dc:rights

• info:eu-repo/semantics/openAccess
• license:Creative commons
• license uri:http://creativecommons.org/licenses/by-nc-nd/4.0/

Language dc:language

eng

Handle dc:identifier

https://hdl.handle.net/11572/489330

OAI identifier oai:identifier

oai:iris.unitn.it:11572/489330