Boron transport properties

Materials based on boron compounds have been explored for many decades because of their exceptional properties in respect to chemical bonding, crystal structure, and phonon and electron conduction. Especially in the field of energy conversion, electron emission, and neutron absorption, borides occupy many niches of application for which no other material can be employed. Until approximately 1980, the main interest in borides always came, however, from basic research aimed at the understanding of their electronic structure, being either responsible for the unique transport properties or the peculiarities in chemical bonding. It is, therefore, no wonder that the most information about borides was at that time created from the viewpoint of physicists and chemists. 

Wood, C., Transport Properties of Boron Carbide, in Boron-Rich Solids, AIP Conf. Proc. 140 (D. Aselage, et al., eds.). Am Inst, of Physics, New York (1986)... 

Even if these general statements on common properties of the boron-rich solids are largely reliable, at present the research on these very promising materials is far from complete. In particular, systematic investigations of interrelations between structural and physical properties have remained in their infancy and are largely restricted to a few materials. Therefore the aim of this chapter is to review the results on electronic structure and electronic transport properties, to demonstrate as far as possible with examples such interrelations between structural and electronic modifications, and to point out the possible extensions of such results to other boron-rich materials. For a complete review of data the reader is referred to Refs. 2 and 3 with updates completed in 1998. 

Information on the electronic properties of a-rhombohedral boron is scarce nevertheless, it proves that its transport properties differ qualitatively, for example, from those of P-rhombo-hedral boron and boron carbide. As discussed in Sec. III.B, the reason is the difference in the... 

Some investigations of the electronic transport properties have been performed by Pistoulet et al. (176-180). The fundamental properties seem to be rather similar to those of P-rhombohedral boron. The material is p type (181), the Hall mobility is small (<1 cm V s ), the Seebeck coefficient is maximum at about 400 K with 470 p. V K and there is a dominating trapping level with an activation energy of 0.39 eV (see Ref. 3 and references therein). 

Investigations of the electronic properties of amorphous boron based on icosahedra are scarce. Some results for the absorption edge are available and yield an absorption edge of about 0.7 eV (38,189,190). Investigations of transport properties are missing. 

H Werheit. On the electronic transport properties of boron carbide. In R Freer, ed. The Physics and Chemistry of Carbides, Nitrides and Borides. Dordrecht Kluwer, 1990, p 677. 

H Werheit, U Kuhlmann, R Eranz, W Winkelbauer, B Herstefl, D Fister, H Neisius. Electronic transport properties of boron carbide within the homogeneity range. In D Emin, T Aselage, AC Switendick, B Morosin, CL Beckel, eds. Boron-Rich Solids, AIP Conference Proceedings 231. Albuquerque AIP, 1990, p 104. 

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