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Kinetics of Enthalpy Relaxation at the Glass Transition in Ternary Tellurite Glasses
Author(s) -
Aida Kazuya,
Benino Yasuhiko,
Dimitrov Vesselin,
Komatsu Takayuki,
Sato Ryuji
Publication year - 2000
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.2000.tb01353.x
Subject(s) - glass transition , enthalpy , ternary operation , fragility , thermodynamics , differential scanning calorimetry , relaxation (psychology) , materials science , activation energy , heat capacity , crystallization , calorimetry , kinetics , chemistry , polymer , physics , psychology , social psychology , computer science , composite material , programming language , quantum mechanics
The kinetics of enthalpy relaxation (recovery) at the glass transition in x K 2 O·(20− x )MgO·80TeO 2 glasses has been examined from heat capacity measurements using differential scanning calorimetry to clarify the features of the structural relaxation in ternary TeO 2 ‐based glasses. Ternary glasses such as 10K 2 O·10MgO·80TeO 2 show high thermal resistance against crystallization compared with binary glasses. The degree of fragility m estimated from the activation energy for viscous flow E η and the glass transition temperature T g is m = 55–62, indicating a fragile character in TeO 2 ‐based glasses. Large heat capacity changes of 43.1–48.2 J·mol −1 ·K −1 are also observed at the glass transition. The activation energy for enthalpy relaxation Δ H is evaluated from the cooling rate dependence of the limiting fictive temperature, and values of Δ H = 897–1268 kJ·mol −1 are obtained. Negative deviation from additivity in Δ H is also observed. Values of the Kovacs–Aklonis–Huchinson–Ramos (KAHR) parameter θ estimated from Δ H and T g are 0.33–0.42 K −1 . It has been proposed that ternary glasses have more homogeneous and constrained glass structure compared with binary glasses.