Structural and Thermoelectric Properties of Cu Substituted Type I Clathrates Ba8CuxSi~32−xGa~14

Abstract

With an attempt to improve the thermoelectric properties of type I clathrates in the Ba-Ga-Si system, we introduce Cu into the framework of the crystal structure. Single crystals are prepared in Ga-flux and characterized by X-ray diffraction techniques and transport measurements for the structural and thermoelectric properties. Our composition analyses show that only a small amount of Cu is determined in the clathrates. The single crystal X-ray diffraction data refinements confirm that Ga atoms prefer the 6c and 24k sites and avoid the 16i sites in the crystal structure. The small amount of Cu affects the crystal structure by compressing the tetrakaidecahedral cage along the direction perpendicular to the six-atom-ring plane. This could be the reason for the high charge carrier concentration, and low electrical resistivity and Seebeck coefficient. We analyze the principal mechanism for our observation and conclude that the Cu substitution can adjust some subtle details of the structure, maintaining the Zintl rule in the type I clathrates.

Thermoelectric Properties of Ba8CuxSiyGe46–x–y Clathrates Synthesized by the Czochralski Method

“…The charge carrier concentration ( n ) in type-I clathrates can be estimated from the Zintl–Klemm concept: for the Ba 8 Cu x Si y Ge 46– x – y clathrate, it is expressed as (Ba 2+ ) 8 (Cu 3– ) x (Si 0 ) y (Ge 0 ) 46– x − y since Cu atoms accept three electrons. , In the actual chemical composition as listed in Table , the value of x increases toward the bottom of the ingot, indicating that the number of electrons accepted by Cu atoms also increases. If the parts are n-type semiconductor, as demonstrated previously for Ba 8 Cu x Si y Ge 46– x – y clathrates ,, and as evidenced later in the Seebeck coefficient results, n should be lower and ρ should be higher toward the bottom of the ingot.…”

A study on the electronic properties of A site and B site doped SrTiO3 for thermoelectric applications using first-principles calculations

“…There is an increased focus on the research to make thermoelectric technology reliable, sustainable, and feasible. Many research groups have investigated various materials like skutterudites, clathrates, tellurides, metallic alloys, and metal oxides [5][6][7][8][9][10]. Among these materials, metal oxide materials are attractive candidates for thermoelectric conversion as they are very abundant, affordable, and non-toxic.…”

A theoretical study of 2D AlN on 3D C4H6N6Ni2 clathrate thermoelectric material composites

“…Nickel diamminebis[m-(cyano-C:N)]bis(cyano-C) di (C 4 H 6 N 6 Ni 2 ) clathrate is as a depiction of phonon glass-electron crystal materials; the clathrate structures have been studied for possible applications in thermoelectricity generation [10][11][12][13][14][15]. Type-I clathrate crystal structure is covalently bonded with the lattice composed of elements primarily from groups 13 and 14 of the periodic table.…”

“…Type-I clathrate crystal structure is covalently bonded with the lattice composed of elements primarily from groups 13 and 14 of the periodic table. Its structure has cages, where metal atoms can fill in [13,16]. Clathrate compounds have been found with high figure of merit (ZT) values of 1.35 Sr 8 Ga 16 Ge 30 .…”