Control of nucleation and crystal growth of a silicate apatitic phase in a glassy matrix

TL;DR

This study investigates how nucleation and crystal growth occur in a silicate glass system, revealing different behaviors based on composition and suggesting potential for waste immobilization.

Contribution

It provides new insights into the crystallization mechanisms and kinetics in a complex oxide glass system, highlighting composition-dependent nucleation and growth processes.

Findings

Ca-rich samples show homogeneous bulk crystallization

Na-rich samples exhibit surface and bulk crystallization with larger crystals

Crystallization activation energy is lower than that of viscous flow and glass transition

Abstract

Nucleation and growth of crystal in an oxide glass was studied in a Si B Al Zr Nd Ca Na O system. The nucleation and growth process was monitored by thermal analysis and isothermal experiments. For the Ca sample the crystallization is homogeneous in the bulk showing a slow increase of crystallinity as temperature increases. The Na rich sample on the other hand go through several crystallization process in the bulk or from the surface, leading to bigger crystals. The activation energy of the viscous flow and the glass transition are of same magnitude when that of crystallization is a lot smaller. Early diffusion of element is done with a mechanism different than the configurational rearrangements of the liquid sate. The global density and small shape of the crystals within the Ca rich matrix confirmed that it would be a profitable waste form for minor actinides.