Thermoelectric properties of single-phase full-Heusler alloy Fe2TiSi films with D3-type disordering

Abstract

Fe2TiSi has been expected to be one of the high-performance thermoelectric full-Heusler alloys. Here, we experimentally clarify the room-temperature Seebeck coefficient (S) and thermal conductivity (κ) for the Fe2TiSi films. Using a molecular beam epitaxy technique, we demonstrate the high degree of L21-ordering and the homogeneous single-phase structure in the Fe2TiSi films. We find that the intrinsic conduction carriers of the Fe2TiSi films are holes and impurity-induced carrier scattering is indicated, derived from weak magnetic moments due to the presence of D03-type (Fe ⇔ Ti) structural disorder in the Fe2TiSi film. From reliable measurements for thin films, the values of S and κ are estimated to be 101 μV/K and 5.6 W/(m K), respectively, at room temperature. This study will open a new way for full-Heusler alloy thermoelectric materials other than those in Fe2VAl systems.

First-principles study of Fe2VAl and Fe2VAl/Si thin films and their magnetic properties

“…In the search for novel high-performance thermoelectric materials, half-and full-Heusler compounds [1][2][3][4][5][6][7][8][9][10][11][12] have been extensively investigated. Many studies have been conducted on the full-Heusler compound Fe 2 VAl and related compounds.…”

Thermoelectric properties of composition-controlled Fe2TiSi-based full-Heusler thin films

“…7,8) It is effective to make use of the seed effects from substrates as investigated in the field of spintronics by using MgO 9) and thermoelectrics by using MgAlO 4 for Fe 2 TiSi. [10][11][12] In thin films, another difficulty is to control the valence electron concentration (VEC) to around 6.00, where FH alloys have a high thermoelectric performance. 3,13) Meanwhile, we succeeded to achieve precise control of film compositions by utilizing sputtering techniques in Fe 2 VAl-and Fe 2 TiAl-based thin films.…”

“…15) It should be noted that S and ρ can be improved by employing other substrates with a small lattice mismatch, such as MgAlO 4, to achieve better crystallinity as previously reported. [10][11][12] The out-of-plane κ at RT was 3.5 W K −1 m −1 ., which is small in comparison to the typical Fe 2 VAl FH bulks. As a result, ZT was 0.36 at room temperature without heavy element doping, which is high enough in FH.…”