Formation of metastable cubic phase and thermoelectric properties in Mg3Bi2 films deposited by magnetron sputtering

Tunable p- and n-Type Tellurium-Free Mg3Bi2 Thermoelectric Thin Films by Thermal Coevaporation

“…We display the PF in Figure S5, with values ranging from 136 to 302 μW m –1 K –2 going from 30 to 200 °C. The PF of our Mg 3 Bi 2 is superior to the typical values found in the literature for Mg 3 Bi 2 . − The thermoelectric figure of merit ZT is around 0.04 at RT, which increases to 0.11 at 200 °C. This is the first report of ZT values for undoped Mg 3 Bi 2 thin films because previous literature did not report on the thermal conductivity.…”

“…The positive Seebeck and Hall coefficients indicate that the Mg-poor Mg 3 Bi 2 thin film has p-type conductivity, as expected from the literature for Mg-deficient compositions. ,,, The low thermal conductivity (κ) of around 1 W m –1 K –1 at RT is comparable to those of other related Mg 3 Bi 2 -based compounds, , although, to the best of our knowledge, an analogous value has not been reported so far for undoped Mg 3 Bi 2 . Regarding the electrical conductivity (σ), we find a value of ∼80 × 10 3 S m –1 , which is higher than the electrical conductivity of Mg 3 Bi 2 thin films deposited with magnetron sputtering. − The Seebeck coefficient across the selected temperature range has values (40–60 μV K –1 ) comparable to those found for the above-mentioned magnetron-sputtered films and increases linearly with temperature. Such a linear increase of S with constant σ has also been observed in other inorganic semiconductor thin films .…”

“…However, the thermal conductivity is not measured, and hence no ZT value can be derived from this work. In another work, Fang et al demonstrated that varying the substrate temperature during the sputtering process induces a phase transition in Mg 3 Bi 2 , with a maximum PF of 110 μW m –1 K –1 at 393 K . Tani et al explored the formation of Mg 3 Bi 2 thin films by postannealing Mg/Bi bilayers prepared by magnetron sputtering .…”

Realizing enhanced thermoelectric performance in an n-type Mg3(Bi,Sb)2-based film

“…6(a) shows the power factor (PF) as a function of temperature for R2 and compared with reported p-type Mg 3 Bi 2 thin films. 40,44 As a result of high Seebeck coefficient, a maximum PF of 132 mW m À1 K À2 at 375 K was achieved for R2 which shows a significant improvement by tuning the composition through co-sputtering. The comparison graph of PF for the present study with reported maximum PF of Mg 3 Bi 2 -based thin films is presented in Fig.…”

“…It should be noted that the power factor of the present work (R2) shows potential to compete with PF of reported p-type thin films. 40,44 To the best of our knowledge, there are no reports on an n-type thin film based on the Mg 3 (Bi,Sb) 2 system. Thus, this work opens a wide area for research in terms of co-sputtering of Mg ions in intrinsic Mg 3 (Bi,Sb) 2 -based thin films for enhanced thermoelectric and power generation devices.…”