Synthesis, structures, electronic structures and physical properties of quaternary alkali, alkaline earth, rare earth and transition metal pnictides
Date
2015
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
University of Delaware
Abstract
Exploration of new materials and understanding the relationship among compositions, structures and physical properties are still a challenge in solid-state chemistry. Based on the Zintl concepts, studing the crystal structures and electronic structures of Zintl phases, it provides a way to further understand and predict the physical properties of solid state materials. Therefore, we systematically investigated a series of quaternary intermetallic compounds containing alkaline, alkaline-earth, rare earth, transition metals, group 13 and 15 elements. By using powder and single crystal X-ray diffractions, the compositions and crystal structures of these phases could be determined. The electronic structures were also calculated from tight-bonding linear-muffin-tin-orbital (TB-LMTO). The physical properties, which include magnetic susceptibilities and electrical resistivities of the compounds were also reported and discussed. This work is divided into two chapters: (1) quaternary pnictides with complex, noncentrosymmetric structures: Synthesis and Structural Characterization of the New Zintl Phases Na11Ca2Al3Sb 8, Na4CaGaSb3, and Na15Ca3In 5Sb12. In this chapter, three new Zintl phases were represented: Na11Ca2Al3Sb8, Na4CaGaSb3, and Na15Ca 3In5Sb12. By discovery of different types of Na cations, which include interlayer and intralayer Na atoms, it provides new examples to prove the importance of cations in chemical bonding and structure formation in Zintl phases. (2) Efficient Tailoring of Band Gap Induced by Rare Earth (RE) Metals Doping: Determining Structure and Properties of Narrow-Gap Semiconductor Ca9- xRExMn 4Sb9 (RE = La, Ce, Pr, Nd and Sm). Several numbers of a new structure family, Ca9-xRE xMn4Sb9 (RE = La, Ce, Pr, Nd and Sm) were synthesized. Due to rare earth inclusion, electrical resistivity of this series showed semi-conductive behavior with very narrow-band gap, compared with poor metallic material Ca9Mn4Bi9 .