Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/97922
標題: Ba8GaxSn30溶液經無方向與單方向固化之相生成
Phase formation of non- and unidirectional solidification of Ba8GaxSn30 solutions
作者: 楊雋懿
Chun-Yi Yang
關鍵字: Ba8Ga16Sn30晶籠化合物
垂直式溶液布里居曼法
Ga溶液
液相線
三元相圖
Ba8Ga16Sn30 clathrate compound
vertical solution Bridgman method
Ga solution
liquidus line
ternary phase diagram
摘要: 本研究選用垂直式Ga溶液布里居曼法嘗試製備出較大晶粒尺寸的P型Ba8Ga16Sn30晶籠化合物。首先調整溶液Ga助熔劑配比,利用降溫曲線法量測各溶液之液相線溫度。隨著Ga比例增加,液相線溫度會有下降趨勢。由此無方向固化所製備出晶體之金相得知,樣本中之γ相Ba(Ga/Sn)4被Ba8Ga16Sn30晶籠化合物所包覆,判斷發生包晶反應。從中觀察到條狀成長的晶體形狀。隨著Ga溶液比例增加,γ相在樣本中比例有所上升。量測得之相變化溫度與EDX分析獲得之成份比例可繪製於Ba-Ga-Sn三元相圖中。並藉由XRD結果證實Ba8Ga16Sn30之α-β相變化之發生。在液相線溫度量測實驗中,量測到γ相生成溫度、Ba8Ga16Sn30生成溫度以及α-β相變化溫度。 由第一階段結果,本研究選用生成最少γ相之Ba8-Ga20-Sn30溶液來藉由垂直式溶液布里居曼法長晶,以單方向固化原理嘗試製備出具大晶粒之P型Ba8Ga16Sn30晶籠化合物之樣本。觀察樣本之金相得知,雖然過量Ga溶液的添加導致晶粒尺寸縮小,但能成功將γ相與Ba8Ga16Sn30分離。在溫度梯度較大條件下製備之樣本,晶粒尺寸較小。而在溫度梯度較小條件下單方向固化能更有效的分離γ相,且晶粒尺寸較大。
In this study, the vertical Ga solution Bridgman method was used for attempt to prepare the P-type Ba8Ga16Sn30 clathrate. First, the Ga flux ratio of solutions was adjusted, and the liquidus temperature of each solution ratio was measured by the cooling curve method. As the proportion of Ga ratio increases, the liquidus temperature decreases. From the metallographic result of the crystal prepared by the non-directional solidification, the γ phase Ba(Ga/Sn)4 in the sample was surrounded by Ba8Ga16Sn30 clathrate. It reveals that a peritectic reaction occurs. A crystal shape of lameller growth was observed therefrom. The proportion of γ phase in the samples increases with the increases of Ga ratio. The measured phase change temperature and composition ratio from EDX analysis can be plotted in the Ba-Ga-Sn ternary phase diagram. The α-β phase transition of Ba8Ga16Sn30 was confirmed by the XRD reasults. In the liquidus temperature measurement experiment, the γ phase formation temperature, the Ba8Ga16Sn30 generation temperature, and the α-β phase change temperature were measured. From the results of first stage, the Ba8-Ga20-Sn30 solution with the least γ phase was used to prepare samples with larger crystals of P-type Ba8Ga16Sn30 clathrate by the vertical solution Bridgman method. From the metallographic result of the samples prepared by the unidirectional solidification, although the addition of the excess Ga solution results in a decrease of the grain size, the γ phase was successfully separated from Ba8Ga16Sn30. The sample prepared under the condition of larger temperature gradient has a smaller grain size. The unidirectional solidification under the condition of smaller temperature gradient can separate the γ phase more effectively and the sample has a larger grain size.
URI: http://hdl.handle.net/11455/97922
文章公開時間: 2021-08-14
Appears in Collections:材料科學與工程學系

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