Amorphization of Li and Al phosphates through mechanical methods

• Grant number: 24/09884-3
• Support Opportunities: Scholarships in Brazil - Master
• Start date: October 01, 2024
• End date: July 31, 2026
• Field of knowledge: Physical Sciences and Mathematics - Physics - Condensed Matter Physics
• Principal Investigator: José Fabián Schneider
• Grantee: Matheus José Ferreira
• Host Institution: Instituto de Física de São Carlos (IFSC). Universidade de São Paulo (USP). São Carlos , SP, Brazil
• Associated research grant: 13/07793-6 - CEPIV - Center for Teaching, Research and Innovation in Glass, AP.CEPID

Abstract

The high-energy mechanical planetary milling process allows the study of structural transformation of materials and chemical reactions, using mechanical energy instead of thermal energy. This is possible due to the fact that in the collisions between the mill spheres and the grains of material, intense pressures are applied with the deposition of high surface energy density. In this way, non-equilibrium states can be produced in materials at room temperature. Mechanical grinding is used in the manufacturing process of solid-state Li-ion batteries with composite electrodes, to obtain a homogeneous mixture of active materials and solid electrolytes, keeping control of particle size. However, the amorphization of materials during the process can significantly decrease ionic conductivity. Alternatively, grinding is a way to synthesize the glassy precursor state of vitro-ceramic electrolytes at low processing temperatures, avoiding evaporation of components. There are still no systematic studies of mechanical amorphization in Li phosphates, which are materials with application in the development of solid electrolytes. In this project we will explore the amorphization process via mechanical grinding of three crystalline phosphates (LiPO3, LiCa(PO3)3 and Al(PO3)3). Using differential scanning calorimetry techniques, we will determine the thermodynamic behavior of the materials obtained, studying structural relaxation, glass transition and crystallization. Using 31P, 27Al, 7Li and 6Li nuclear magnetic resonance techniques, we will analyze the local structure of the materials as a function of milling time and grinding energy, identifying and quantifying the degree of amorphization. From this study, we seek to elucidate two fundamental questions about mechanical amorphization: (i) does amorphization occur discontinuously, through local melt- quench events, or via the progressive accumulation of defects in the crystalline structure?, (ii) the structure of the amorphous glass obtained in the mechanical process is the same as that of a glass obtained from the thermal method, from melt and quench?