博士 / 國立交通大學 / 應用化學研究所 / 98 / In this dissertation, all selenide compounds were synthesized by solid state method. These structures were determined and investigated with X-ray diffraction of single crystals. Calculations of the density of states, measurements of Seebeck coefficient and electrical conductivity confirm that these compounds are p- or n-type semiconductors with a narrow band gaps.
Firstly, New ternary and quaternary chalcogenides Sn3-xPbxBi2Se6 (x = 0 - 0.7) were synthesized and crystallize in the orthorhombic space group Pnma (No. 62). The structure for these compounds is related to Pb3Bi2S6 with an atomic position near the cell-twining plane with lillianite homologous series L(4, 4). The ternary phase contains partially occupied Sn site and a quaternary system exhibits a phase width in the range of 0 ≦ x ≦ 0.7. Single-crystal structure analysis indicates that there is a correlation between the Pb composition and position shift of M5 site from the cell-twining plane. Band structure calculations confirmed that the structure is more stable when the position of M5 site is shifted away the cell-twining plane.
Secondly, quaternary chalcogenides PbxSn6-xBi2Se9 (x=0 – 4) crystallizes in orthorhombic space group Cmcm (No. 62) and isostructural to the mineral heyrovskyite, Pb6Bi2S9. The PbxSn6-xBi2Se9 features a three-dimensional framework containing slabs of NaCl-(311) type with lillianite homologous series L(7, 7) . PbxSn6-xBi2Se9 exhibits identical layers of 7 octahedra wide slabs and each slab is composed of fused rectangular [M12Se12] rod units that are expanded along direction [010].
In the third section, quaternary selenides Sn2Pb5Bi4Se13 and Sn8.65Pb0.35Bi4Se15 were synthesized and crystallize in monoclinic space group C2/m (No.12). These compounds exhibit tropochemical cell-twinning of NaCl-type structures with lillianite homologous series L(4, 5) and L(4, 7) for Sn2Pb5Bi4Se13 and Sn8.65Pb0.35Bi4Se15, respectively. Measurements of electrical conductivity indicate that these materials are semiconductors with narrow band gaps; Sn2Pb5Bi4Se13 is n-type, whereas Sn8.65Pb0.35Bi4Se15 is a p-type semiconductor with Seebeck coefficients -80(5) and 178(7) μV/K at 300K, respectively.
Finally, quaternary chalcogenides Pb13Sb2.08Bi1.92Se19 was synthesized and crystallize in monoclinic space group C2/m (No.12), with lattice parameters of Pb13Sb2.08Bi1.92Se19: a = 14.127(3) Å, b =4.2625(8) Å, c = 34.477(6) Å, β= 96.329(4)°, R1/wR2 = 0.0351/0.0822 and GOF = 1.045. These structures reveal novel structure type. Pb13Sb2.08Bi1.92Se19 features a three-dimensional framework containing alternate layers of 7 and 8 octahedra wide slabs of NaCl-(311) type with lillianite homologous series L(7, 8). The semiconductor properties are confirmed with electronic calculations, Seebeck coefficient and electrical conductivity measurements.
| Identifer | oai:union.ndltd.org:TW/098NCTU5500031 |
| Date | January 2010 |
| Creators | Chen, Keui-Bo, 陳奎伯 |
| Contributors | Lee, Chi-Shen, 李積琛 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | en_US |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 111 |
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