新穎硒化物Mn2Sn7Bi4Se15與In3.87Pb4.44Sb4.52Se17的合成與特性分析

Abstract

本論文成功以固態燒結法分別在1023和1173K的溫度下，合成一具有新穎結構和礦物vikingite結構之新穎硒化合物，晶系屬於單斜體，空間群分別為P21/m (No. 11)和C2/m (No. 12)。Mn2Sn7Bi4Se15晶體結構由兩層不同厚度的NaCl（311）結構單元平行c軸無限延伸，晶格常數為a=13.708(3), b=4.1571(8)、 c=26.500(5)、 b=96.20(3), V=1501.2(5) Å3、 Z=2、 R1=3.97%、 wR2=9.58% 和GOF=1.042。In3.87Pb4.44Sb4.52Se17晶體結構分別由NaCl-[100]和CdI2-type兩種不同的結構單元組成，晶格常數為a=17.813(4), b=4.0847(8)、 c=23.914(5)、 b=111.56(3), V=1618.2(6) Å3、 Z=2、 R1=4.90%、 wR2=12.24% 和GOF=1.035，此結果經過比對ICSD資料庫及SciFinder資料庫確認為一新穎結構硒化物。 從導電度的測量得知，In3.87Pb4.44Sb4.52Se17的電阻率隨溫度上升而下降，屬於半導體行為，從UV-VIS漫反射式吸收光譜得知，半導體能隙約為0.73 eV。Mn2Sn7Bi4Se15化合物室溫的Seebeck量測值約100μV/K到200μV/K之間，屬於P型半導體，在磁性性質方面，為順磁性且過渡金屬為高自旋狀態。

New selenides Mn2Sn7Bi4Se15 and In3.87Pb4.44Sb4.52Se17 were prepared by directly reacting the elements in stoichiometric ratios at 1023K and 1173K, respectively. These compounds crystallized in the monoclinic system with space group C2/m (No.12) and P21/m (No. 11), respectively. Mn2Sn7Bi4Se15 is isostructural to the vikingite type that features three-dimensional framework with building units of NaCl（311） types units running parallel to the c-axis. Mn2Sn7Bi4Se15 crystallizes in a monoclinic space group C2/m with a=13.708(3), b=4.1571(8)、 c=26.500(5)、 b=96.20(3), V=1501.2(5) Å3、 Z=2、 R1=3.97%、 wR2=9.58% and GOF=1.042. The structure of In3.87Pb4.44Sb4.52Se17 has a three-dimension framework assembled from two NaCl-[100] and CdI2-type modular units running along the b-axis. In3.87Pb4.44Sb4.52Se17 crystallize in the monoclinic space group P21/m with a=17.813(4), b=4.0847(8)、 c=23.914(5)、 b=111.56(3), V=1618.2(6) Å3、 Z=2、 R1=4.90%、 wR2=12.24% and GOF=1.035. The resistivity decrease with increasing temperature for In3.87Pb4.44Sb4.52Se17, indicative of semiconducting behaviors. Diffuse-reflectance spectra show that the band gaps of In3.87Pb4.44Sb4.52Se17 are about 0.73 eV. According to the Seebeck coefficient measurements, Mn2Sn7Bi4Se15 is p-type semiconductor. Temperature dependence susceptibilities measurements indicate paramagnetic property for Mn2Sn7Bi4Se15 and high-spin for Mn.