Influence of Selenium Oxide on Structure and Properties of New Zinc Boroselenite Glasses

Abstract

The traditional melt quenching method was used to prepare new zinc boroselenite glasses in the system xSeO₂·(50 − x)ZnO·50B₂O₃ with varying SeO₂/ZnO molar ratio. X-ray diffraction patterns (XRD) have revealed an amorphous structure in glasses of up to 40 mol pct SeO₂. On the other hand, the presence of sharp diffraction peaks on the XRD spectra of samples containing 40 and 50 mol pct SeO₂ confirms a formation of some polycrystalline phases distributed in the host glass network. Based on FTIR and NMR data, the glass structure at a short-range order exhibited a similar value of the fraction of tetrahedral boron (N₄), particularly, for both samples of 0 and 5 mol pct SeO₂. In this situation, SeO₂ is as well as ZnO both played a modifier role. On the other hand, increasing SeO₂ on expense of ZnO decreases the N₄ fraction gradually. However, in SeO₂-rich glass, most of boron atoms are mainly placed in three coordinated sites in BO₃ units coordinated with SeO₄ groups. Decreasing N₄ fraction and increasing crystallization confirmed that SeO₂ operates as a glass former and mainly as a crystalline agent. The results based on the TEM of the selected area of electron diffraction patterns (EDP) agree well with the ones obtained by XRD. The diffraction patterns clearly displayed two sets of diffraction rings: one is caused by boroselenite nanocrystals and the other by zinc selenite. In contrast, a broader halo of dispersed structure, known as an amorphous structure, is present in the diffraction pattern obtained from SeO₂-free glass.