Phonon Scattering through
a Local Anisotropic Structural
Disorder in the Thermoelectric Solid Solution Cu<sub>2</sub>Zn<sub>1–<i>x</i></sub>Fe<sub><i>x</i></sub>GeSe<sub>4</sub>
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Abstract
Inspired by the promising thermoelectric properties of
chalcopyrite-like
quaternary chalcogenides, here we describe the synthesis and characterization
of the solid solution Cu<sub>2</sub>Zn<sub>1–<i>x</i></sub>Fe<sub><i>x</i></sub>GeSe<sub>4</sub>. Upon substitution
of Zn with the isoelectronic Fe, no charge carriers are introduced
in these intrinsic semiconductors. However, a change in lattice parameters,
expressed in an elongation of the <i>c</i>/<i>a</i> lattice parameter ratio with minimal change in unit cell volume,
reveals the existence of a three-stage cation restructuring process
of Cu, Zn, and Fe. The resulting local anisotropic structural disorder
leads to phonon scattering not normally observed, resulting in an
effective approach to reduce the lattice thermal conductivity in this
class of materials