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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]