Effect of thermal treatment pathway on the solid-state formation of Zn₃B₂O₆

Abstract Zn₃B₂O₆ was synthesized by a solid-state reaction method using zinc sulfate and boric acid precursors. The effects of precursor composition and thermal treatment pathway on crystallization and phase formation were investigated using direct and stepwise calcination routes. The synthesized products were characterized by PXRD, FT-IR, SEM, UV–Vis spectroscopy, XRF, and thermal analyses (TGA/DTA). PXRD results confirmed the formation of monoclinic β-Zn₃B₂O₆ under optimized synthesis conditions. Comparative diffraction analyses showed that stepwise calcination combined with intermediate grinding improved crystallinity and reduced amorphous background contribution compared with direct calcination. FT-IR spectra indicated the presence of borate structural units mainly composed of BO₃ groups together with Zn–O-related vibrations. SEM observations revealed agglomerated particles with heterogeneous morphology characteristic of solid-state crystal growth. Thermal analyses indicated stable behavior of the synthesized phase over a broad temperature range. The results demonstrate that precursor stoichiometry and thermal treatment pathway strongly influence crystallization and phase development during Zn₃B₂O₆ formation. Stepwise calcination promoted improved crystallinity and stabilization of monoclinic β-Zn₃B₂O₆ synthesized by solid-state reaction.