The structural, electronic, elastic and high thermoelectric properties of a new Zintl compound Ba3Sn3Sb4 studiedby first principles
Year: 2020
Type: article
Abstract: The structural, electronic, elastic, and thermoelectric properties of a new recently synthetized Zintl compound Ba3Sn3Sb4 are studied using the first principles and the Boltzmann theory. We determine the requirements of the chemical potentials for the formation of Ba3Sn3Sb4. On the basis of the mechanical stability criteria and the phonon spectrum of Ba3Sn3Sb4, the lattice structure is determined to be thermodynamically stable. The electron density difference of Ba3Sn3Sb4 shows that there is an ionic bond between Ba and the [Sn3Sb4] cluster, and a covalent Sn–Sb bond in [Sn3Sb4]. The coexistence of ionic and covalent bonds indicates that Ba3Sn3Sb4 is a typical Zintl compound. The calculated electronic band structure shows that Ba3Sn3Sb4 is an indirect semiconductor with a band gap ~0.29 eV. In the conduction bands, the presence of multivalley bands benefits the thermoelectric properties. In terms of the Slack model, the lattice thermal conductivity κl is smaller than 0.5 W m−1 K−1 when the temperature is over 720 K. On the basis of the analysis of the band structure, we calculate the thermoelectric properties using the Boltzmann theory. The results show that p-type-doped Ba3Sn3Sb4 undergoes interesting changes. Because pristine Ba3Sn3Sb4 is an n-type semiconductor, the Seebeck coefficient of p-type-doped Ba3Sn3Sb4 changes from negative to positive at T=500 K or T=700 K. For p-type-doped Ba3Sn3Sb4, the calculated largest ZT is 0.09. For n-type-doped Ba3Sn3Sb4, the Seebeck coefficient exhibits bipolar effects at T>500 K. This result is obtained because thermal excitation becomes strong with an increase in the temperature, and the effect of the minor carriers leads to the change of the S value. The optimized largest ZT value of n-type-doped Ba3Sn3Sb4 is up to 0.26 with n=1.14×1020 cm−3 at T=700 K, which is almost three times that of p-type-doped Ba3Sn3Sb4.
Authors: DongWei MA, Jing ZHANG, HuiJuan GENG, Di YUAN, Gui YANG
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W3010984061