Structural, Phonon, Electronic and Thermoelectric Properties of Zr 0.25 Ti 0.75 GeSb
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TRUCTURE OF MATTER AND QUANTUM CHEMISTRY
Structural, Phonon, Electronic and Thermoelectric Properties of Zr0.25Ti0.75GeSb A. Fazeli Kisomia, B. Nedaee-Shakaraba,*, A. Boochanib, H. Akbaria, and S. J. Mousavic a Department
of Physics, Ardabil Branch, Islamic Azad University, Ardabil, Iran of Physics, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran c Department of Physics, Rasht Branch, Islamic Azad University, Rasht, Iran * е-mail: [email protected]
b Department
Received December 31, 2019; revised February 29, 2020; accepted April 11, 2020
Abstract—This paper explores structural, phonon, electronic and thermoelectric properties of Zr0.25Ti0.75GeSb. By doping 0.25 Zr to TiGeSb the space group of this compound changes to P4/mm. Lattice constants and bulk modulus demonstrate relative increase compared to TiGeSb. This increment is low and expected. Furthermore, phonon calculations of Zr0.25Ti0.75GeSb were carried out by Quantum Espresso code. Electronic and thermoelectric calculations were performed using Wien2k software and accessory code Boltztrap. This compound has metallic nature and contribution of i orbitals among atoms with d orbital for atom “Ti1” is the highest. In thermoelectric properties, figure of merit of Zr0.25Ti0.75GeSb is significantly increased compared to bulk of TiGeSb in both xx and zz directions at low temperatures. However, at high temperatures it is lower. Keywords: Zr0.25Ti0.75GeSb, density functional theory, phonon properties and thermoelectric properties DOI: 10.1134/S0036024420130117
1. INTRODUCTION Since the discovery of Heusler compounds in about 120 years ago [1, 2], these compounds have been continuously appealing for researchers and constantly demonstrate their new and fascinating attributes. From structural viewpoint, Heusler compounds have two chemical formula X2YZ and XYZ. X2YZ is known as full Heusler compounds, consisting of 4 fcc interpenetrated sub lattices from X, X', Y, and Z. X and Y are usually transition metals, Y can also be rareearth metals too, while Z is from main group elements (s or p). If one of the sub lattices becomes empty, compound will change to formula XYZ which is called Half–Heusler compounds with C1b symmetry. Most of Half–Heusler compounds illustrate various properties. They could present as semiconductor, metal, half metal, ferromagnetic, anti-ferromagnetic and so on [3–5]. Therefore, it is not surprising that there is a great interest in Heusler compounds in research [6–8]. From electronic point of view, there is a clear relation between chemical formula of Heusler compounds and complication of chemical binding. Recently, a new kind of Half-Heusler compounds has been discovered that TiGeSb is one of them. These compounds consist of two elements from main group (s or p), one transition metal in XYZ formula and a tetrag-
onal structure [9]. TiGeSb is a suitable option for application in microelectronic and optoelectronic industries [10, 11]. It is also appropriate for thermoelectric devices [12]. TiGeSb demonstrates excellent chemical
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