钠紫青铜NaMo_6O_(17)的热电势研究

Thermoelectric Power Study of Sodium Molybdenum Purple Bronze

报道了在 １０～３００ Ｋ 温度范围内，对准二维电荷密度波导体 Ｎａ Ｍｏ６ Ｏ１７紫青铜热电势的测量结果． 在８０ Ｋ 附近， Ｎａ Ｍｏ６ Ｏ１７ 的热电势发生突变是该物质存在 Ｐｅｉｅｒｌｓ 相变的又一个实验例证． 温度高于８０ Ｋ 时，热电势可以用一个经验公式： Ｓ＝ Ａ Ｔ＋ Ｂ／ Ｔ 来描述；而在温度低于 ３０ Ｋ 时，热电势可以拟合为： Ｓ＝ Ａ Ｔ＋ Ｂ Ｔ３ ， 说明总的热电势均存在着来自载流子自身的热扩散和声子对载流子的散射两方面的贡献，但高温区和低温区声子对载流子的散射机制是不一样的． 总的热电势值揭示，无论 Ｐｅｉｅｒｌｓ 相变前后，主要载流子均是电子． 上述这些实验结果与 Ｋ Ｍｏ６ Ｏ１７的实验结果比较，有助于进一步加深对紫青铜结构、 Ｐｅｉｅｒｌｓ

The measurement result of the thermoelectric power(TEP) of a quasi\|two\|dimensional conductor NaMo 6O 17 , which exhibits charge density wave properties, was reported. The TEP abnormality in vicinity of 80 K( T p) is another good proof for the Peierls phase transition of this compound. When T>T p, the TEP data can be fitted with the traditional formula: S=AT+B/T , however, the TEP data can be fitted more properly with formula of S=AT+BT 3 when the temperature is below 30 K. These results show that the TEP of NaMo 6O 17 is consist of two major contributions: the diffusion of carriers and the phonon diffraction effects on carriers, and the mechanic of the diffraction is likely different above and below T p. The TEP value shows that the major carrier is electron in the whole temperature range. The comparisons of these results with those of KMo 6O 17 should contribute to further understanding of the effects that alkali metal ions have on some important physical properties, such as the structure of the purple molybdenum bronze and Peierls phase transition.