鋇鎵鍺晶籠熱電合金的成份、鍵結與價帶能譜之分析

Composition, Bonding and Valence Band Spectrum Analysis of BaGaGe Clathrate Thermoelectric Alloys

林以淳(Yi-Chun Lin)

指導教授 ： ARRAY(0xa9d1e30)

中原大學/工學院/化學工程研究所/碩士(2010年)

https://doi.org/10.6840/cycu201000723

摘要

本研究以X光光電子能譜儀(XPS)針對BaGaGe晶籠材料進行分析。分析項目包括成分、化學位移以及價帶能譜，探討XPS成份定量的準確性、BaGaGe材料的化學鍵結以及其價帶與熱電特性之關係。
研究發現以XPS定量分析BaGaGe晶籠材料所得之成份比例與用質譜儀分析結果有所差異，應該是因為光電子衰減長度誤差所造成。運用此差異可算出衰減長度之修正因子。在鍵結狀態方面，本研究由鍵結量與成分變化之關係成功判斷出BaGaGe晶籠材料中各種鍵結的光電子束縛能。然而，以合金價帶理論推算出的熱電力變化趨勢與實驗所發現不同，推估是因為材料為多相結構、含有Ge析出相且樣本含有孔洞，這些因素都對價帶產生影響複雜，因此簡單理論模型並不適用。

關鍵字

化學位移 ； 價帶 ； 熱電 ； X光光電子能譜儀 ； BaGaGe晶籠 ； 成份分析

並列摘要

In this study, BaGaGe materials were analyzed by the X-ray Photoelectron Spectroscopy (XPS). Analysis items included compositional analysis, chemical shift, and valence band spectra. The accuracy of XPS composition quantification, chemical bonding in BaGaGe materials, and the relation between the valence band and thermoelectric properties were also investigated.
The results showed that some differences were observed between the compositions of BaGaGe clathrates measured by XPS quantification and by mass spectroscopy analysis. This difference is believed causing from the error in the escaping depth of photoelectrons. The correction factor for the escaping depth can be calculated from that difference. For the bonding state study, the binding energies of photoelectrons for the specific bonds in BaGaGe clathrates were successfully evaluated from the variations in both bond quantity and material composition. However, the variation tendency of the thermoelectric power with composition disagreed with that deduced from the valence band theory for metals and alloys. It is proposed that the multiphase structure, Ge precipitate, and voids in the BaGaGe materials have complicate influences on valence band and therefore resulted in this discrepancy. A simple model is shown not applicable for the BaGaGe clathrates.

並列關鍵字

chemical shift ； valence band ； thermoelectric. ； compositional analysis ； BaGaGe clathrates ； X-ray Photoelectron Spectroscopy

參考文獻

42 張振崴，以電弧熔煉法製備高熱電優值N型鋇鎵鍺合金與其真空熱壓後之熱電表現，中興大學材料科學與工程學系碩士學位論文，2009，第30、38頁。

24 H. Anno, M. Hokazono, M. Kawamura, J. Nagao, K. Matsubara, “Thermoelectric properties of Ba8GaxGe46-x clathrate compounds”, Proceedings of the 21st international conference on thermoelectrics, IEEE, NY, 2002, p. 77.

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