Electronic and thermoelectric properties of alkali metal-based perovskites CsYbF3 and RbYbF3
Q Mahmood1,2, †, N A Noor3, T Ghrib1,2, Nessrin A Kattan4, Asif Mahmood5,, ‡, and Shahid M Ramay6
1 Basic and Applied Scientific Research Center, Imam Abdulrahman Bin Faisal University, P. O. Box 1982, 31441, Dammam, Saudi Arabia 2 Department of Physics, College of Science, Imam Abdulrahman Bin Faisal University, P. O. Box 1982, 31441, Dammam, Saudi Arabia 3 Department of Physics, Riphah International University, Lahore, Pakistan 4 Department of Physics, Faculty of Science, Taibah University, Medina, Saudi Arabia 5 Chemical Engineering Department, College of Engineering, King Saud University, Riyadh, Saudi Arabia 6 Physics and Astronomy Department, College of Science, King Saud University Riyadh, Riyadh, Saudi Arabia
The electronic and thermoelectric properties of alkali metal-based fluorides CsYbF3 and RbYbF3 are studied by using Wien2k and BoltzTraP codes. The structural and thermodynamic stability of these materials are confirmed by tolerance factor (0.94 and 0.99 for RbYbF3 and CsYbF3) and negative formation energy. The optimized lattice constants and bulk moduli are consistent with the results reported in the literature. The reported band gap for RbYbF3 is 0.86 eV which decreases to 0.83 eV by the replacement of Cs with Rb. The electrical and thermal conductivities along with Seebeck coefficients decrease with temperature rising from 0 K to 800 K. The large values of thermoelectric parameters for positive chemical potentials show that the character is dominated by electrons. The studied materials have figures of merit 0.82 and 0.81 at room temperature respectively, for RbYbF3 and CsYbF3 and increase with temperature rising. Therefore, the materials under study may have potential application values in thermoelectric generators and refrigerators.
Received: 03 May 2020
Revised: 04 May 2020
Accepted manuscript online: 18 June 2020
Fund: Two of the authors, Asif Mahmood and S M Ramay, were supported by the Deanship of Scientific Research at King Saud University (Grant No. RGP-311).
Q Mahmood, N A Noor, T Ghrib, Nessrin A Kattan, Asif Mahmood, and Shahid M Ramay Electronic and thermoelectric properties of alkali metal-based perovskites CsYbF3 and RbYbF3 2020 Chin. Phys. B 29 117305
Fig. 1.
(a) Electronic structures, (b) energy band structure, figures of merit of (c) CsYbF3, (d) RbYbF3, and (e) calculated crystal structure of Rb/CsYbF3 formed by Xcrysden.
Fig. 2.
Plot of optimized energy verses volume of CsYbF3 (red) and RbYbF3 (black) calculated by PBEsol approximation.
Parameter
RbYbF3
CsYbF3
a0/Å
4.60, 4.53a
4.67, 4.61a
B0/GPa
41.86
37.62
Δ H/(eV/unit cell)
−2.50
−2.26
Band gap Eg(Γ−Γ)/eV
0.86
0.83
Table 1.
The calculated values of lattice constant a, bulk moduli B, enthalpy of formation Δ H, and band gap of fluoride-based perovskites RbYbF3 and CsYbF3.
Fig. 3.
Electronic band structures of (a) RbYbF3 and (b) CsYbF3 calculated by PBEsol+mBJ potential.
Fig. 4.
Electrical conductivity of RbYbF3 and CsYbF3 against (a) chemical potential and (b) temperature.
Fig. 5.
Thermal conductivity of RbYbF3 and CsYbF3 against (a) chemical potential and (b) temperature.
Fig. 6.
Seebeck coefficient of RbYbF3 and CsYbF3 against (a) chemical potential and (b) temperature.
Fig. 7.
Power factor of RbYbF3 and CsYbF3 against (a) chemical potential and (b) temperature.
Fig. 8.
Figure of merit (ZT) of RbYbF3 and CsYbF3 against (a) chemical potential and (b) temperature.
Perovskites
σ/1018 (Ω ⋅ m ⋅ s)−1
κ/1014 (W/mK)−1
S/(μV/K)
σS2/1012 (W/mK2 ⋅ s)
ZT
RbYbF3
3.76
0.230
130.44
0.639
0.82
CsYbF3
3.86
0.235
128.60
0.638
0.81
Table 2.
Calculated room temperature values of electrical conductivity (σ), thermal conductivity (κ), Seebeck coefficient (S), power factor (σ S2), and figure of merit (ZT) for fluoride-based perovskites RbYbF3 and CsYbF3.
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