Dynamic Specific Heat, Glass Transition, and Non-Debye Nature of Thermal Relaxation in Lithium Borate Glasses(Condensed matter: structure and mechanical and thermal properties)

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The physical properties of lithium borate glasses, xLi_2O・(100-x)B_2O_3, vary anomalously with the lithium oxide content, known as "borate anomaly". In this study, the compositional variations of the dynamic glass transition temperature T^ω_g and the non-Debye nature (or stretched exponentiality β_<KWW>) in the vicinity of T_g have been investigated over a wide composition range. Since T^ω_g depends on the frequency of the temperature modulation, a more precise composition dependence can be discussed. The trend of T^ω_g shows a single broad maximum at about x=26-28. Moreover, the composition dependence of the non-Debye behavior has been presented. It shows a broad maximum at about x=40mol%. It is found that β_<KWW> is systematically controlled using the fraction of each intermediate structural unit, particularly the tetrahedron composed of the 4-coordinated boron atom. Both the composition dependences of T^ω_g and β_<KWW> can be explained using the structure-superposition model.
社団法人日本物理学会の論文
2008-08-15