X-Ray Absorption Fine Structure of Ti Coordination Changes in Na2O-B2O3-SiO2-TiO2 Glass System

Abstract

The Na₂O-B₂O₃-SiO₂-TiO₂ glass was prepared by adding 8 wt % TiO₂ into the basic glass 10Na₂O-50B₂O₃-40SiO₂ (mol %). Application Ti K-edge X-ray absorption fine structure (XAFS), the change of Ti structure during the glass phase separation process was mainly investigated. Glass phase separation and TiO₂ crystallization of the samples were characterized by X-ray diffraction, scanning electron microscope and transmission electron microscope. The results indicated that Ti⁴⁺ formed [TiO₄] tetrahedral structure in high-temperature homogeneous glass of Na₂O-B₂O₃-SiO₂-TiO₂ system. At low temperature heat treatment (500 °C) Ti⁴⁺ entirely transformed from [TiO₄] to [TiO₆] and then formed nucleus pre-group and anatase crystal nucleus, which were advantageous to crystallize TiO₂. With the increasing of heat-treatment temperature, Ti-ion structure is closed to that of anatase and TiO₂ began to crystallize at heat-treatment 550 °C.