Glass transition and crystallization kinetics of Na2O – B2O3 – Nb2O5 – Bi2O3 ceramic glasses

Abstract

A series of Na2O – B2O3 – Nb2O5 – Bi2O3 glasses are synthesized, and their differential thermal analysis (DTA) thermograms are explored at different heating rates. Based on the DTA thermograms, the glass transition temperature (Tgl) and the crystallization peak temperature (Tpc) along with the activation energy of glass transition (EGl) and the activation energy of crystallization (Epc) were determined. The results revealed a decrement of Tgl and EGl upon increasing the Nb2O5 + Bi2O3 content from 0 to 0.15, then, both Tgl and EGl increase beyond this limit. Meanwhile, there is a decrement in the values of Tpc and Epc with a continuous increment of the Nb2O5 + Bi2O3 content. The behavior of the thermal parameters is correlated to the structural variations in the glass network as a function of the Nb2O5 + Bi2O3 content. The XRD curves of the explored glasses indicate the presence of the polycrystalline phases Na2B4O7, BiNbO4, BNbO4 in the amorphous matrix.