Subamorphous Thermal Conductivity of Crystalline Half-Heusler Superlattices

Abstract

The quest to improve the thermoelectric figure of merit has mainly followed the roadmap of lowering the thermal conductivity while keeping unaltered the power factor of the material.Ideally an electron-crystal phonon-glass system is desired. In this work, we report an extraordinary reduction of the cross-plane thermal conductivity in crystalline (TiNiSn):(HfNiSn) half-Heusler superlattices. We create SLs with thermal conductivities below the effective amorphous limit, which is kept in a large temperature range (120-300 K).We measured thermal conductivity at room temperature values as low as 0.75 W m -1 K -1 , the lowest thermal conductivity value reported so far for half-Heusler compounds. By changing the deposition conditions, we also demonstrate that the thermal conductivity is highly impacted by the way the single segments of the superlattice grow. These findings show a huge potential for thermoelectric generators where an extraordinary reduction of the thermal conductivity is required but without losing the crystal quality of the system.

Modification of the Raman Spectra in Graphene-Based Nanofluids and Its Correlation with Thermal Properties

“…The measurements of thermal conductivity of the nanofluids were carried out by using the well-known three-omega (3ω) method [51,52] in the bidirectional configuration [53,54]. An extended description of the setup can be found in the section on experimental methods in the supporting information of References [27,55]. The effective viscosity of the nanofluids was measured using a Haake RheoStress RS600 rheometer from Thermo Electron Corp. at T = 20–21 °C.…”

Heat Transport Control and Thermal Characterization of Low-Dimensional Materials: A Review

“…On the other hand, the introduction of very small-periods (10s of nm) have also shown a large impact on lowering k. Values close or smaller than the amorphous limit of one (or both) component of the SLs have been reported. Costescu et al [64], Pernot et al [65], and Chavez-Angel et al [66] measured cross-plane thermal conductivity values (k⊥) below the amorphous limit of Al2O3, Si, and HfNiSn in Al2O3:W, SiGe:Si and HfNiSn:TiNiSn SLs, respectively. Niemelä et al [67] also overtook the amorphous limit of TiO2 using organic-inorganic (TiO2):(Ti-O-C6H4-O) SLs.…”

“…et al[64], Pernot et al[65], and Chavez-Angel et al[66] measured cross-plane thermal conductivity values (k ⊥ ) below the amorphous limit of Al 2 O 3 , Si, and HfNiSn in Al 2 O 3 :W, SiGe:Si and HfNiSn:TiNiSn SLs, respectively. Niemelä et al [67] also overtook the amorphous limit of TiO 2 using organic-inorganic (TiO 2 ):(Ti-O-C 6 H 4 -O) SLs.…”

Review of coherent phonon and heat transport control in one-dimensional phononic crystals at nanoscale

“…[84][85][86] These predictions were experimentally confirmed in various amorphous and crystalline superlattices. [87][88][89] However, this ultra-low thermal conductivity is mainly attributed to the incoherent phonon scattering.…”