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Study of thermal behaviour of 30Li 2 O·70TeO 2 glass by X‐ray dynamic observation
Author(s) -
Taniguchi Taketoshi,
Inoue Satoru,
Mitsuhashi Takefumi,
Nukui Akihiko
Publication year - 2000
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889899012625
Subject(s) - differential scanning calorimetry , phase (matter) , diffractometer , differential thermal analysis , endothermic process , analytical chemistry (journal) , lithium (medication) , materials science , thermal decomposition , glass transition , phase transition , crystallization , supercooling , crystallography , chemistry , diffraction , thermodynamics , crystal structure , optics , medicine , physics , organic chemistry , adsorption , chromatography , composite material , endocrinology , polymer
The thermal behaviour of a 30Li 2 O·70TeO 2 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 TeO 2 appears during decomposition of vitreous 30Li 2 O·70TeO 2 of the initial phase. After that, the thermal changes of the lithium tellurite and the TeO 2 components proceed independently. The LT‐ X phase converts to α‐Li 2 Te 2 O 5 , and the vitreous TeO 2 phase is followed by crystallization of an α‐TeO 2 phase. In the endothermic process between 673 and 793 K, the α‐Li 2 Te 2 O 5 phase transforms into a β‐Li 2 Te 2 O 5 phase and the minor crystalline α‐TeO 2 phase melts. Then, β‐Li 2 Te 2 O 5 incongruently melts to form Li 2 TeO 3 and a molten TeO 2 phase. Li 2 TeO 3 continuously melts at around 763 K. The results show a possibility of reversible change between the α‐Li 2 Te 2 O 5 and the β‐Li 2 Te 2 O 5 phases.