Characteristic Phonon Spectrum of Negative Thermal Expansion Materials with Framework Structure through Calorimetric Study of Sc2M3O12 (M = W and Mo)
Characteristic Phonon Spectrum of Negative Thermal Expansion Materials with Framework Structure through Calorimetric Study of Sc2M3O12 (M = W and Mo)
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DOI：
10.1021/cm900965p
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发表时间：
2009-06
影响因子：
8.6
通讯作者：
Y. Yamamura;Satoaki Ikeuchi;Kazuya Saito
中科院分区：
文献类型：
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作者：
Y. Yamamura;Satoaki Ikeuchi;Kazuya Saito
为了研究负热膨胀(NTE)化合物的结构特征与声子性质的关系，测量了Sc2W3O12和Sc2Mo3O12的热容。热容的光谱分析提供了它们的有效声子态密度(DOS)。Sc_2W_3O_(12)的声子态呈现三个特征：负模格朗森参数(γ_i)约为5 meV的低能声子模，高能声子模，声子态密度分裂成两个间隔较大的区域。γIci的相对贡献，其中Ci是每个振动模i的热容，揭示了具有负γi的低能声子模引起了nTE，后两个特征是保持nTE在较宽温度范围内所必需的。Sc_2Mo_3O_(12)具有负γ_i的低能模式，这一事实表明，Sc_2Mo_3O_(12)即使在其正的热膨胀的低温阶段也可能具有非平衡热膨胀性质。声子DOS与其他氧化物的比较表明，p。
To study the relation between the structural characteristics and the phonon property in the negative thermal expansion (NTE) compounds, the heat capacities of Sc2W3O12 and Sc2Mo3O12 were measured. Spectrum analysis of heat capacity provided their effective phonon densities of states (DOS). The DOS of Sc2W3O12 shows three features; low-energy phonon modes with negative mode-Gruneisen parameter (γi) around 5 meV, high-energy phonon modes, and separation of phonon DOS into two regions with a wide gap. The relative contribution of γiCi, where Ci is heat capacity of each vibrational mode i, reveals that the low-energy phonon modes with negative γi cause the NTE and that the latter two features are necessary to maintain the NTE in a wide temperature range. Sc2Mo3O12 has the low-energy mode with the negative γi. This fact indicates that Sc2Mo3O12 potentially has the NTE property even in its low-temperature phase showing positive thermal expansion. A comparison of the phonon DOS with other oxides shows that the p...