Preparation and Thermoelectric Properties of Iron Disilicide

Authored by: Yukihiro Isoda , Haruhiko Udono

Thermoelectrics and its Energy Harvesting

Print publication date:  April  2012
Online publication date:  April  2016

Print ISBN: 9781439874707
eBook ISBN: 9781439874714
Adobe ISBN:

10.1201/b11891-21

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Abstract

The stoichiometric compound iron disilicide (FeSi2) is composed of environment-friendly, nontoxic, and abundantly available elements. According to the equilibrium phase diagram established by Piton and Fay,1 FeSi2 causes the metal–semiconductor transition at the peritectoid temperature of 1259 K, as shown in Figure 18.1.26 The low-temperature phase β-FeSi2, which belongs to the Cmca space group of the orthorhombic crystalline structure,7 possesses stable semiconducting properties up to 1259 K. Above this peritectoid temperature, the metallic phase is a eutectic alloy composed of the tetragonal α-phase8,9 and the cubic ε-phase.10,11 The crystallographical notation of the α-phase is FeSi2 or Fe1−ϒSi2 (ϒ: vacancies of the iron sublattice); however, it exists within a rather wide range of compositions through the accommodation of vacancies in the iron sublattice. The compound with 20% vacancies is represented by the chemical formula Fe2Si5. The ε-phase is iron monosilicide FeSi with space group P213. The eutectic and peritectoid temperatures of the eutectic alloy (Fe-66.7 at% Si) are 1485 and 1259 K, respectively. The β-FeSi2 phase transforms into the α-Fe2Si5 phase and ε-FeSi phase above 1259 K as follows: β-FeSi2→α-Fe2Si5+ε-FeSi.

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