Chapter 4 An overview of recent developments for BiSb Alloys

Abstract

Publisher Summary This chapter reviews the recent developments for bismuth–antimony (Bi–Sb) alloys. It describes the main physical properties of Bi–Sb alloys and their synthesis. The chapter discusses the salient results pertaining to thermoelectric properties for both single crystalline and polycrystalline materials. The chapter focuses on the Bi–Sb alloys in the Bi-rich region. Transport properties are only described qualitatively, because the band structure is strongly correlated to antimony content and temperature. Although the thermomagnetic effects present considerable interest in Bi–Sb solid solutions, the chapter discusses the zero-field coefficients. The chapter summarizes the basic features of the band structure of the pure elements and alloys pertinent to the understanding of the transport properties. The small distortion from the simple cubic lattice induces that bismuth and antimony are semimetals characterized by a small overlap of the fifth and sixth bands, leading to the presence of a small equal number of electrons (n) and holes (p) at all temperatures. In isotropic monovalent metals or in extrinsic semiconductors, where only one type of cartier is present, the carrier density n and mobility μ may be easily experimentally determined by using the Hall coefficient, RH. The knowledge of cartier density and mobility in the temperature range 80–200 K is of the greatest interest from the point of view of the use of Bi–Sb alloys in thermoelectric devices. In Bi–Sb alloys, the thermal conductivity λ is principally the sum of two terms: an electronic contribution λE (including both unipolar and bipolar terms) and a contribution associated with the lattice λL.