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Transparent glass-ceramics based on ZnO–Al 2 O 3 –SiO 2 (ZAS) glass system exhibit excellent optical and mechanical properties that are dependent on crystal grains. Gahnite (ZnAl 2 O 4) was the main phase that crystallized in ZAS glass-ceramics via thermoelectric coupling treatment. The morphology and size of ZnAl 2 O 4 crystal were controlled by the electric field strength. Introduction of thermoelectric coupling field led to the refinement and dispersion of large and agglomerated ZnAl 2 O 4 crystal grains, which improved the transmission and Vickers' hardness of the ZAS-based glass-ceramics. Theoretical calculations revealed that crystal phase is the area of low electric field strength, which resulted in the migration of Zn ions (Zn2+) from glass phase to the ZnAl 2 O 4 crystal regions under the effect of thermoelectric coupling field. The decrease in the amount of Zn2+ in glass phase further limited its grain growth, and refinement of ZnAl 2 O 4 grains was achieved. This research shows an efficient and rapid approach to refine grains in ZAS glass-ceramics by application of thermoelectric coupling treatment. • In this work, it is the first time use of thermoelectric coupling field to precipitate ZnAl 2 O 4 nanocrystals in ZnO–Al 2 O 3 –SiO 2 glass-ceramics. • The application of a thermoelectric coupling field was used to refine and uniformly distribute ZnAl 2 O 4 crystals in ZnO–Al 2 O 3 –SiO 2 glass-ceramics. • The mechanism of a thermoelectric coupling field on crystal refinement is explained in detail, which provides ideas for the refinement and uniformly distribution of crystal grains. [ABSTRACT FROM AUTHOR]

The Li 2 O–Al 2 O 3 –SiO 2 (LAS) glass ceramics are prepared by one-step thermoelectric treatment. The influence of thermoelectric treatments on LAS glass-ceramics were studied. The crystal phase composition and microstructure of the LAS glass-ceramics were investigated by DSC, SEM, XRD and FTIR. Moreover, the thermal expansion performance and light transmittance of LAS nanocrystalline glass were characterized. The results show that low-expansion transparent LAS nanocrystalline glass can be produced in a short time by thermoelectric treatment. The free energy of nucleation and the degree of polymerization of the glass network are reduced by the electric field. The key is that the electric field polarizes Ti and Zr ions at the crystallization temperature, so that the crystal nuclei repel the same poles. This allows uniform crystal distribution, promotes crystallization and reduces one-step crystallization of crystal agglomeration. This proves that the rapid preparation of nanocrystalline glass by the one-step method is feasible, and provides a reference for the future one-step processing of glass-ceramics. • Thermoelectric treatment promotes crystallization in LAS nanocrystalline glass. • It eliminates crystal agglomeration in LAS nanocrystalline glass. • It can rapidly produce low-expansion transparent LAS nanocrystalline glass. [ABSTRACT FROM AUTHOR]