Dwelling deep into the anisotropic transport of Zintl Ca3Sb2

• Published in: Materials science & engineering. B, Solid-state materials for advanced technology Vol. 279; p. 115677
• Main Authors: Gajaria, Trupti K., Jani, Shivam, Chakraborty, Brahmananda, Jha, Prafulla K.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01.05.2022; Elsevier BV
• Subjects: Anharmonicity; Anisotropy; Ca3Sb2; Current carriers; Density functional theory; Figure of merit; Heat conductivity; Heat transfer; Phonons; Power factor; Temperature dependence; Thermal conductivity; Zintl compound; Zintl compound; Thermal conductivity; Ca3Sb2
• ISSN: 0921-5107; 1873-4944
• DOI: 10.1016/j.mseb.2022.115677

•Novel Zintl compound Ca3Sb2 with ultra-low thermal conductivity of 0.26 Wm-1K−1 at 300 K has been predicted.•A potential thermoelectric compound with figure of merit ZT of 0.72 at 300 K. Phonon-glass-electron-crystal (PGEC) is a class of materials that exert electron crystal like pronounced electronic conduction and glass like supressed thermal conduction leading to astonishing thermoelectric (TE) performance. The density functional theory based investigation of Zintl Ca3Sb2 is presented. We find that a narrow band gap of 0.35 eV and the spatially dispersed phonon branches of Ca3Sb2 result in improved power factor and ultra-low thermal conductivity. Comparing with conventional TE materials PbTe, Bi2Te3 and Mg3Sb2, the Ca3Sb2 possesses significantly low average thermal conductivity (κL) of 0.26 Wm-1K−1 at 300 K. The root-cause of such a feeble κL is reciprocated in terms of the acoustic modes with supressed vibrational frequency that when coupled with lower lying optic phonon modes, results in significantly high phonon scattering rates and phonon anharmonicity. Interestingly, the thermal conduction along the cross-plane direction is found to be much more supressed than the in-plane direction suggesting appreciable anisotropy. The TE efficiency of Ca3Sb2 is envisaged from the temperature dependent profile of figure of merit ZT which is found to attain magnitude of ∼ 0.72 (in z-direction) within temperature range 300 K-600 K for both charge carriers. Besides providing in-depth insight to the thermal conduction, the study provides motivation to investigate this yet-to-be-synthesized potential Zintl compound.