An influence of a glass composition on the structure and properties of Bi₂O₃–B₂O₃–SiO₂–ZnO glass system with addition of BaO, CaO and Fe₂O₃

The Bi₂O₃–B₂O₃–SiO₂–ZnO glass system with addition of network modifier (BaO, CaO and Fe₂O₃) were synthesized using the conventional melt quenching method. The effect of chemical compositions on the glass network structure, thermal properties, crystallization characteristics and electrical properties were systematically investigated. With rising the Bi₂O₃ content, the number of [BiO₃] and [BiO₆] units increases and a new bridging of Bi–O–B bond forms. Moreover, either the increase of Bi₂O₃ content or the decrease of SiO₂ content induce a progressive conversion of [BO₄] into the [BO₃] unit. However, the influence of a network modifier on the conversion of [BO₄] to [BO₃] unit depends on the composition. An addition of network modifier helps stabilize the glass structure against a crystallization. A high content of Bi₂O₃ and ZnO promotes the formation of Bi-rich and Zn-rich crystals during heat-treated process, respectively. The Bi content of Bi-rich crystal increases and the Zn-rich crystal decomposes with increasing the heat-treated temperature. Both of the glass network structure and the formation of Bi-rich crystal in glass matrixes during testing process combine to determine the change rule of the CTEs (coefficients of thermal expansion). The variation of the T_g (glass transition temperature) only depends on the glass network structure. The dielectric constant of glasses without network modifier decreases with decreasing the Bi₂O₃ content. Moreover, an addition of network modifier could decrease the dielectric constant. Each glass offers a dielectric loss tangent below 0.005 and an electrical resistivity above 10⁷ Ω cm.