Study of thermal behaviour of 30Li₂O·70TeO₂glass by X-ray dynamic observation

Abstract

The thermal behaviour of a 30Li2O·70TeO2 glass was studied by use of an in situ high‐temperature X‐ray diffractometer equipped with a position‐sensitive detector (PSD). The dynamical structural changes were also observed by differential thermal analysis (DTA) and differential scanning calorimetry (DSC) measurements. Differences and contradictions exist in previous studies related to the phase relation at high temperature, including the process of phase change. It is found that in the exothermic process after a glass transition between 553 and 623 K, an unknown phase of lithium tellurite (LT‐X) crystallizes at first. At almost the same temperature, a minor component of vitreous TeO2 appears during decomposition of vitreous 30Li2O·70TeO2 of the initial phase. After that, the thermal changes of the lithium tellurite and the TeO2 components proceed independently. The LT‐X phase converts to α‐Li2Te2O5, and the vitreous TeO2 phase is followed by crystallization of an α‐TeO2 phase. In the endothermic process between 673 and 793 K, the α‐Li2Te2O5 phase transforms into a β‐Li2Te2O5 phase and the minor crystalline α‐TeO2 phase melts. Then, β‐Li2Te2O5 incongruently melts to form Li2TeO3 and a molten TeO2 phase. Li2TeO3 continuously melts at around 763 K. The results show a possibility of reversible change between the α‐Li2Te2O5 and the β‐Li2Te2O5 phases.

Induced crystallization on tellurite 20Li2O–80TeO2glass

“…The technological applications of these glasses require a profound comprehension of several properties. In this context, structural [3][4][5] and electrical properties [6] were investigated in order to understand all important aspects of these glasses. Nowadays, the technological use of tellurium-based glasses is a reality that justifies progressive investigations on optical, structural and electrical properties [7,8].…”

<I>In Situ</I> High-Temperature X-ray Observations of Crystallization of Zinctellurite Glass

“…When the glass crystallizes, the α-TeO 2 and the ZnTeO 3 phases were found to crystallize first, followed by the crystallization of the Zn 2 Te 3 O 8 phase. Nukui et al 8) reported that the predominant crystallization of the ZnTeO 3 phase from the glass attributes to the inhmogeneity of the glass structure, even though the phase is generally unexpected. While dur- ing the cooling process from the melt, the α-TeO 2 phase was found to crystallize first, followed by the crystallization of the Zn 2 Te 3 O 8 phase.…”

“…In situ observations are useful in directly obtaining data of thermal behavior. 8) Furthermore, the X-ray system can be used to produce rapid measurements, and thus, direct comparison can be made with DTA results, with respect to structural changes and thermal reactions. The crystallization behavior of the 20ZnO·80TeO 2 glass will be discussed in terms of the Temperature-Time-Transfer (T-T-T) diagram.…”