Adichtchev S V, Malinovsky V K, Ignatieva L N, Merkulov E B, Surovtsev N V
Institute of Automation and Electrometry, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090, Russia.
Institute of Chemistry, Far East Branch of Russian Academy of Sciences, Vladivostok 690022, Russia.
J Chem Phys. 2014 May 14;140(18):184508. doi: 10.1063/1.4875095.
Low-frequency (down to 30 GHz) inelastic light scattering is studied in a multicomponent glass ZBLAN (ZrF4-BaF2-LaF3-AlF3-NaF) in a wide temperature range. The contributions of the THz vibrational spectrum (boson peak) and of the fast relaxation are extracted and analyzed. It is shown that the fast relaxation spectrum is described by a distribution of relaxation times leading to a power-law ν(α) dependence in the frequency range 30-300 GHz. Temperature dependence of α(T) is well described by the Gilroy-Phillips model, while the integrated intensity of the fast relaxation increases significantly with the temperature. This feature distinguishes the fast relaxation in ZBLAN from the case of most single-component glasses. Thermodynamic and kinetic fragility indexes are significantly different for the ZBLAN glass. The correlations between the boson peak intensity, elastic moduli, and fragility index, found earlier for single-component glasses, are fulfilled for the thermodynamic fragility index of ZBLAN. In contrast, the correlation between the fast relaxation intensity at Tg and the fragility holds better for the kinetic fragility index of ZBLAN. We propose that thermodynamic and kinetic fragilities reflect different aspects of glassy dynamics in the case of glass formers with the complex chemical composition and structure topology: the former correlates with the elastic properties and the boson peak, the latter with the relaxation.
在宽温度范围内研究了多组分玻璃ZBLAN（ZrF4-BaF2-LaF3-AlF3-NaF）中的低频（低至30 GHz）非弹性光散射。提取并分析了太赫兹振动光谱（玻色子峰）和快速弛豫的贡献。结果表明，快速弛豫光谱由弛豫时间分布描述，在30-300 GHz频率范围内导致幂律ν(α)依赖性。α(T)的温度依赖性可用吉尔罗伊-菲利普斯模型很好地描述，而快速弛豫的积分强度随温度显著增加。这一特征将ZBLAN中的快速弛豫与大多数单组分玻璃的情况区分开来。ZBLAN玻璃的热力学和动力学脆性指数有显著差异。单组分玻璃中先前发现的玻色子峰强度、弹性模量和脆性指数之间的相关性，对于ZBLAN的热力学脆性指数是成立的。相比之下，对于ZBLAN的动力学脆性指数，Tg处的快速弛豫强度与脆性之间的相关性更好。我们提出，在具有复杂化学成分和结构拓扑的玻璃形成体中，热力学和动力学脆性反映了玻璃态动力学的不同方面：前者与弹性性质和玻色子峰相关，后者与弛豫相关。
