新穎四元過渡金屬硒化物Ag0.46Mn1.08Pn2.46Se5 (Pn = Sb, Bi)的合成，鑑定與特性分析

Abstract

在本篇論文裡，我們使用三相圖在TM1/TM2/Pn/Se (TM1, TM2 = transition metal; Pn = main group element)系統中尋找新穎四元過渡金屬硒化物，並且將所有的產物經由X光粉末繞射來進行鑑定。在Ag/Mn/Pn/Se (Pn = Sb. Bi)系統裡，發現到有未知相的存在，並藉由X光單晶繞射儀解析其結構，此外對其物理性質及電子結構進行計算分析討論。Ag0.46Mn1.08Pn2.46Se5 (Pn = Sb, Bi)是以固態燒結法在923K溫度下，合成出具有Pavonite homologous series P (5,1)結構之化合物。它們的晶系皆屬於單斜體，空間群為C2/m，其中Ag0.46Mn1.08Bi2.46Se5晶格常數為a = 13.418(3) Å, b = 4.0973(8) Å, c = 16.987(3) Å, β = 93.369(3)o, Z = 4，Ag0.46Mn1.08Sb2.46Se5晶格常數為a = 13.290(4) Å, b = 4.030(1) Å, c = 16.866(4) Å, β = 94.428(3) o, Z = 4。Ag0.46Mn1.08Bi2.46Se5在高溫時是呈現順磁性，當溫度將到極低時是為反鐵磁性，而Ag0.46Mn1.08Sb2.46Se5在5~350K街為鐵磁性。在電性量測部分，兩個化合物的導電度是隨著溫度上升而上升，是一半導體特性。反射光譜得知兩化合物能隙分別為0.66和0.85 eV。由Seebeck係數量測知Ag0.46Mn1.08Bi2.46Se5為n型半導體，在溫度568K時係數為-745 μV/K，而Ag0.46Mn1.08Sb2.46Se5為p型半導體，在溫度608K時係數為249 μV/K。電子結構計算顯示與物理量測互相吻合。

New quaternary selenides in TM1/TM2/Pn/Se (TM1, TM2 = transition metal; Pn = main group element) system was synthesized. All products were characterized by powder X-ray diffraction and these structures were determined by single crystal X-ray diffraction. The relationships between physical properties and electronic structures were also investigated. Two quaternary transition metal selenides, Ag0.46Mn1.08Pn2.46Se5 (Pn = Sb, Bi) were synthesized by solid state method at 923K. Both structures crystallize in the monoclinic system (Ag0.46Mn1.08Bi2.46Se5: space group C2/m, a = 13.418(3) Å, b = 4.0973(8) Å, c = 16.987(3) Å, β = 93.369(3)o, Z = 4; Ag0.46Mn1.08Sb2.46Se5: space group C2/m, a = 13.290(4) Å, b = 4.030(1) Å, c = 16.866(4) Å, β = 94.428(3) o, Z = 4). These compounds are isostructual with the AgBi3S5 that contains two types of layered slabs classified as the Pavonite homologous series P (5,1). The magnetic property of Ag0.46Mn1.08Bi2.46Se5 is Cuire-Weiss paramagnet at high temperature and undergoes antiferromagnetic ordering at low temperature. The Ag0.46Mn1.08Sb2.46Se5 well shows ferromagnetic behavior. The increase of electrical conductivity with increasing temperature indicates both compounds are semiconductors. The optical band gaps are 0.66 and 0.85 eV for Ag0.46Mn1.08Bi2.46Se5 and Ag0.46Mn1.08Sb2.46Se5, respectively. Measurements of Seebeck coefficient indicate n-type for Ag0.46Mn1.08Bi2.46Se5 (-745 μV/K. at 568 K) and p-type semiconductor for Ag0.46Mn1.08Sb2.46Se5 (249 μV/K at 608 K). These experimental results are corroborated by electronic band structure calculations.