新穎四元硒化物TMxSn7-xIn10Se22 (TM = Fe, Co, Ru) 與 Ag3Ge2.57Sb7.35Se15的合成，鑑定與特性分析

Abstract

在本篇論文中，我們以固態燒結法合成四元硒化物，並藉由X光單晶繞射儀解析其結構。此外，我們也研究了這些化合物的物理性質與結構特徵。 第一部分中，我們主要探討過渡金屬的存在對於結構形成有一定的幫助。其結構與 Sn5.5In11S22為相同結構，為單斜晶系，空間群為 P2/m(No.10)。晶體結構由三種不同的單元所組成：(1)由 M4-M5 及 M6-M7 各自形成之菱形柱狀單元；(2) M8-M9 形成一平面層狀單元；(3) M1-M3 十面體單元。由磁化率的量測與計算我們推測 Co 為正三價。藉由導電度的量測均可發現三種硒化物皆具有導電度隨著溫度升高而升高的現象，說明三種化合物皆為半導體。Ru0.7Sn6.31In9.99Se22 的 Seebeck 係數量測可得其為一 n-type 半導體。由理論計算也可得到具有狹窄能隙的電子結構及不同金屬與Se之間的鍵結特性。 而在第二部分裡，我們合成且得到一單晶 Ag3Ge2.57Sb7.35Se15。此化合物為單斜晶系，空間群為Cm(No. 8)，其晶格常數為 a = 13.5098(10) Å, b = 4.0844(3) Å, c = 26.329(2) Å, β = 104.8370(10)°, V = 1404.4(2) Å3, Z = 2, 及 R = 0.043，屬於 Lillianite 結構並可以 L(10,1) 表示。我們藉由兩顆不同組成的單晶，經過些許的調整之後，我們以一空間中直線方程式來表示此化合物的純相範圍。並且藉由粉末繞射的幫助，我們可以訂出此化合物為純相的範圍。純相樣品進行導電度的量測可得此化合物在純相範圍的能隙是落在0.51 eV to 0.71 eV之間。

The thesis contains two parts. In part (1), four ternary and quaternary selenides TMxSn7-xIn10Se22 (TM = Fe, Co, Ru) were synthesized and the effect of transition metals to the formation of the target structure was studied. The as-synthesize phase is isostructural to Sn5.5In11S22 that crystalized in monoclinic system with space group P2/m(No.10). The crystal structure contains three building units of rhombus (M4-M5 and M6-M7), planar (M8-M9) and dodecahedrons (M1-M3). The oxidation state of Co is +3, which was supported by magnetic susceptibility analysis. Electrical conductivity measurements revealed semiconducting property for all phases. The Seebeck measurement for Ru0.7Sn6.31In9.99Se22 exhibits n-type semiconducting property. Theoretical calculations show narrow band gap and bonding characters of different metals and Se. In part (2), we obtained a new quaternary selenide Ag3Ge2.57Sb7.35Se15, which crystallizes in the monoclinic space group Cm (No.8) with a = 13.5098(10) Å, b = 4.0844(3) Å, c = 26.329(2) Å, β = 104.837(1)°, V = 1404.4(2) Å3, Z = 2, and R = 0.043. The crystal structure contains two slabs that can be classified as the Lillianite homologous series noted as L (10, 1). A phase width was obtained with the help of two isostructural compounds with different compositions and powder X-ray diffraction. The electrical conductivity of pure phase sample shows narrow band gap in the range of 0.51 eV to 0.71 eV.