Study of the effect of mixed modifiers on the relaxation time of phosphate glasses

• Grant number: 25/15537-7
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: September 01, 2025
• End date: August 31, 2026
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Nonmetallic Materials
• Principal Investigator: Edgar Dutra Zanotto
• Grantee: Giovanna Bogni Rossi
• Host Institution: Centro de Ciências Exatas e de Tecnologia (CCET). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil
• Associated research grant: 13/07793-6 - CEPIV - Center for Teaching, Research and Innovation in Glass, AP.CEPID

Abstract

Structural relaxation occurs spontaneously in vitreous materials, as they are thermodynamically out of equilibrium. This phenomenon can be accelerated by thermal treatments near the glass transition region, leading to gradual changes in properties over time. A recent study by our research group (not published yet) showed that, in glasses containing a single network modifier, the structural relaxation time is similar to the stress relaxation time of the corresponding supercooled liquid. However, in compositions with mixed modifiers, these times appear to be decoupled. This project aims to investigate the hypothesis that such decoupling between relaxation times is related to a mixed-modifier effect. To test this, a systematic study will be conducted using the series 0.5 (x MgO ¿ (1¿x) BaO) ¿ 0.5 P2O5, with x = 0, 0.25, 0.50, 0.75, and 1. These five phosphate glass compositions will be synthesized, and structural relaxation will be monitored through variations in refractive index, while stress relaxation will be evaluated via rheological measurements in the glass transition region. The results are expected to reveal whether the presence of mixed modifiers influences the correlation between structural and shear relaxation mechanisms, contributing to a deeper understanding of the effects of composition on the relaxation dynamics of glasses. (AU)