含錫之新穎熱電材料的合成與分析

Abstract

本論文中主要在兩種不同的系統中發現三種新化合物，並對三種化合物做了結構與物性的分析。第一個系統為含Ta、Sn、Se的三元化合物，其合成溫度為1223K，得到一銀灰色的針狀化合物，反應的比例為Ta：Sn：Se=1：1：4，為一針狀化合物，推測可能與TaSe3有相似的結構，由調控Sn的含量可以確定Sn在此化合物中扮演一個特別的角色，結構上的分析仍在進行中，初步得到一個monoclinic的結構，可能的單位晶格為a=12.130(3) Å, b=3.510(1) Å, c=24.620(7) Å , β=100.7(2)°, V=1030.7(4) Å3；第二個系統為Sn-Bi-Se之三元化合物，反應溫度在1073K，其晶系為monoclinic，空間群為P21/c，單位晶格為：a=31.393(9) Å, b=4.1622(1) Å, c=32.067(9) Å , β=117.68°, Z=4 , V=3710.4(2) Å3，R1/wR2= 0.124/0.327，其結構包含新穎之層狀結構；第三個系統為AgSnBi3S6之四元化合物，其合成溫度為1073K，其晶系為orthorhombic ，空間群為Pna21，a=20.086(1) Å , b = 13.310(7) Å, c=4.054(2) Å,α＝β＝γ＝90°,Z=4,V=1083.7(1) Å3，R1/wR2=0.037/0.107，此結構與Ag-Pb-Bi-S有相同之層狀結構單元，AgSnBi3S6之Seebeck 係數在580K為-175μV/K，相關化合物AgPbBi3S6之Seebeck係數在580K則為-900μV/K。

In this report, three new ternary and quaternary compounds were synthesized and characterized. Ⅰ：The new ternary chalcogenide was synthesized by tantalum, tin and selenium in 1:1:4 ratio. Preliminary results of this study indicate that the Sn element played an important role in the formation of the needle shape compound. The color is silver gray and looks like hair. The structure analysis is in progress. Ⅱ： SnxBiySez system：this compound is synthesized by initial composition of “Sn5Bi6Se14” at 1073K. The structure was determined by single-crystal X-ray diffraction. Preliminary result reveals a possible formula of Sn10Bi18Se37, which is a new compound with novel layer structure. The compound crystallizes in the monoclinic space group P21/c with a=31.393(9) Å, b=4.1622(1) Å, c=32.067(9) Å, β=117.68°, Z=4, V=3710.4(2) Å3, and the final R values is R1/wR2= 0.124/0.327. Ⅲ： The AgSnBi3S6 compound was synthesized by composition “AgSn4Bi4S10” at 1073K. The single crystal structure analysis reveals that the Ag-Sn-Bi-S is isostructure to the mineral AgPbBi3S6. The structure was determined by single-crystal X-ray diffraction and the compound crystallizes in the orthorhombic space group Pna21 with a=20.086(1) Å , b = 13.310(7) Å, c=4.054(2) Å, Z=3, V=1083.7(1)Å3, and the final R values is R1/wR2= 0.037/0.107. The Seebeck coefficient of AgSnBi3S6 and the isostructure compound AgPbBi3S6 at 580K can reach to -175μV/K and -900μV/K respectively.