Decelerated crystal growth in a soda-lime-silica glass.

• Kinetics of crystal growth in silicate glasses is quantitatively modelled. • Growth kinetics is governed by the viscosity of the diffusion zone. • Accumulation of residual melt components causes viscosity change. • Activation enthalpy increases in time with crystal size. Isolated Na 2 O⋅2CaO⋅3SiO 2 (NC2S3) single crystals grew at temperatures above glass transition in a melt with a slight soda excess. The enrichment of Na in the continuous solid solution Na 4+2z Ca 4–z [Si 6 O 18 ] (with 0 ≤ z ≤ 1) upon crystallisation causes a depletion of soda of the growing interfacial diffusion zone. Therefore its viscosity will change. Experimental data and idealized model calculations of the viscosity show the same trend and indicate that the viscosity of the interfacial zone would be up to several orders of magnitude higher than the viscosity of the melt. This increased viscosity at the crystal growth front and the experimentally observed decrease of the crystallisation velocity with crystal size suggest a linear increase of the effective activation enthalpy of the diffusional transport through the diffusion zone with crystal size, which allows to quantitatively model crystal growth data of the NC2S3 glass investigated. [ABSTRACT FROM AUTHOR]