鉿鎳錫與鈮鈷錫錫化物材料之合成及其熱電性質研究

Synthesis of HfNiSn and NbCoSn Stannide Materials and their Thermoelectric Properties

黃亘佑(Syuan-You Huang)

指導教授 ： 吳新明

大同大學/工程學院/材料工程學系所/碩士(2010年)

摘要

具半赫斯勒結構之HfNiSn及NbCoSn合金，具有出色的熱電性質。此類合金具有MgAgAs型式之結構。本研究選取初始成份為化學計量Hf1Ni1Sn1、Nb1Co1Sn1及其附近之成份進行機械合金化球磨。合成之粉末並經退火處理觀察其結構變化，經由真空熱壓製成塊材，探討生成單一HfNiSn及NbCoSn合金材料之熱電性。利用X光繞射分析所得粉末及塊材之結構，並配合Rietveld refinement，分析所得結構之特性。X光繞射結果發現對於初始成份為Hf1Ni1Sn1，無論球磨或球磨後加以退火處理，皆可得到單一相之半赫斯勒HfNiSn粉末。對於Nb1Co1Sn1初始成分，球磨後得到非晶組織。若再加以退火處理，可得到單一相之半赫斯勒NbCoSn粉末。對於偏離Hf1Ni1Sn1之附近成份球磨結果顯示，除初始成分Hf30Ni40Sn30形成非晶相外，其餘成份皆可得到半赫斯勒HfNiSn相。當對上述粉末進行退火處理，其結構雖仍以半赫斯勒HfNiSn相為主，但也伴隨著出現Hf2Ni2Sn相、HfNi2相、或Ni3Sn4與Ni3Sn2混合相。對於上述二初始成份化學計量分別為Hf1Ni1Sn1、Nb1Co1Sn1經球磨後，再經熱壓及緻密化處理皆可獲得單一相之半赫斯勒塊材，且室溫下所得之最佳ZT值分別為0.007與0.005。

關鍵字

X光繞射 ； 熱壓 ； 機械合金化 ； 半赫斯勒 ； 結構演化

並列摘要

The HfNiSn and NbCoSn alloys with half-Heusler structure have been regarded as possessing excellent thermoelectric properties. Such alloys have MgAgAs-type crystal structure. In this study, starting compositions of stoichiometric Hf1Ni1Sn1, Nb1Co1Sn1 and in their vicinity were selected to carry out mechanical alloying. The milled powder mixtures were subjected to annealing treatment to observe the structural changes, and to vacuum hot-pressing to produce bulk materials in order to explore the feasibility of generating thermoelectric alloys with a single HfNiSn or NbCoSn phase. X-ray diffraction analysis was employed to analyze the structure of the powders and bulk materials, and with the Rietveld refinement the characteristics of each phase were analyzed. X-ray diffraction results showed that for the starting Hf1Ni1Sn1 composition, regardless of milling or milling plus subsequent annealing, a single phase of half-Heusler HfNiSn powder could be produced. As for the starting Nb1Co1Sn1 composition, prolong milling produces no crystalline phase. Instead, an amorphous structure is finally obtained. If an annealing treatment was further imposed on such an amorphous structure, a single phase of half-Heusler NbCoSn powder was obtained. For other compositions in the vicinity of stoichiometric Hf1Ni1Sn1 , milling on these powders produces less pure half-Heusler HfNiSn together with small amounts of other phases. When these milled powders were undergone annealing treatment, a half-Heusler HfNiSn phase was dominated and accompanied by Hf2Ni2Sn, HfNi2, or Ni3Sn4 and Ni3Sn2 mixture phase. For the above-mentioned two stoichiometric Hf1Ni1Sn1 and Nb1Co1Sn1 compositions, hot-pressing the milled powders and followed by densification produce bulk materials with a single half-Heusler HfNiSn and NbCoSn phase, and the values of figure of merit at room temperature for these two alloys are 0.007 and 0.005, respectively.

並列關鍵字

structure evolution ； X-ray diffraction ； hot-pressing ； mechanical alloying ； half-Heusler

參考文獻

[1] C. Yu, T. J. Zhu, R. Z. Shi, Y. Zhang, X. B. Zhao, J. He, Acta Materialia, 57 (2009) p. 2757.

[2] F. J. DiSalvo, Science, 285 (1999) p. 703.

[5] G. A. Slack, in Solid State Physics, Academic Press, New York, Vol.34 (1979) p. 1.

[8] D. M. Rowe, Thermoelectrics Handbook: Macro to Nano, CRC(2006).section 1.

[13] L. Offernes, P. Ravindran, C. W. Seim, A. Kjekshus, Journal of Alloys and Compounds, 458 (2008) p. 47~p. 60.