Investigation of optoelectronic and thermoelectric properties of half-metallic BaRuO 3 using DFT+U

Khalil

et al. 2020

Mater. Res. Express

We have examined structural, electronic and optical properties of TM-GaO 3 (TM=Sc, Ti, Ag) perovskite oxides by means of first Principles study based on density functional theory (DFT). TM represents transition metal elements. To investigate structural properties, exchange correlation potential was determined by employing Full Potential Linearly Augmented Plane Wave (FP-LAPW) technique along with Perdew-Burke-Ernzerhof -GeneralizedGradient Approximation (PBE-GGA) functional. Moreover, Hubbard U eff parameter LDA+U was used to overcome limitations of PBE-GGA functional. All compounds TM-GaO 3 (TM=Sc, Ti, Ag) seem semi-conductor in nature because indirect band gap in each case has been observed with energies 1.33 eV, 0.75 eV and 1.95 eV, respectively. Partial density of states (PDOS) analyses portrayed that 3d orbitals of Sc & Ti, 4d orbital of Ag, and 2p orbital of anions contribute mainly to increase electronic conductivity of the studied compounds. Charge density contour plots depicted ionic nature of TM-cations, while, significant sharing of isolines between O and Ga atoms showed covalent character between them. These contours have also confirmed accumulation of charges around O atoms. Optical analysis revealed that the considered perovskite oxides show sharp increase in optical conductivity and absorptivity in higher energy range when energetic photons are incident upon. Remarkably, they displayed poor reflectivity. However, defect states introduced in the band gap region might be due to cations. These composites are suitable for photovoltaics and other optoelectronic applications OPEN ACCESS RECEIVED

Section: Introductionmentioning

confidence: 99%

Investigations of structural, electronic and optical properties of TM-GaO₃ (TM = Sc, Ti, Ag) perovskite oxides for optoelectronic applications: a first principles study

Khalil

et al. 2020

Mater. Res. Express

“…This work has proved that only BaRuO 3 oxide stabilized in the (2H) phase and showed a ferromagnetic role. We recall that during our previous publications in which we have studied the optoelectronic and magnetic properties of BaRuO 3 and BaRuO 3 ; the results obtained have affirmed that the BaRuO 3 with cubic structure and space group Pm-3m was a half-metallic ferromagnetic [17] and the GdRuO 3 with orthorhombic structure and space group Pnma was semiconductor antiferromagnetic A-type [18]. Alloys are produced in order to improve the materials properties or to give them exceptional properties.…”

Section: Introductionmentioning

confidence: 61%

“…To model our Gd x Ba 1−x RuO 3 alloy, we have used two supercells 2 × 2 × 2: one is cubic (parent structure of the BaRuO 3 compound [17]) (Fig. 1a) and the other is orthorhombic (parent structure of the GaRuO 3 compound [18]) (see Fig.…”

Section: Methodsmentioning

confidence: 99%

Predictive study of ferromagnetism and antiferromagnetism coexistence in Ba1-xGdxRuO3 induced by Gd-doping

Labdelli

Hamdad

2021

Rev. Mex. Fís.

Some ferromagnetic alloys which adopt the perovskite or double-perovskite structure exhibit some remarkable properties, such as electromagnetic effects, charge and orbital ordering, i.e., dielectric and magnetoresistance effects in the same time. These phenomena are related to both electrical conductivity and spin orbit orientation. In order to optimize and explore the structural, magnetic and electronic properties of GdxBa1-xRuO3 alloy, we investigated here the first-principles calculations using the generalized gradient approximation (GGA+U+SO) as implemented in the Wien2K package. The concentration classification of GdxBa1-xRuO3 alloy with (x = 0, 0.125, 0.25, 0.5, 0.875, 1) is given. In this work, we have identified features such transition phases, spin ordered and charge conduction that enable a priori of both crystal structure and magnetic behavior prediction.Our considerable GdxBa1-xRuO3 alloy is a half-metallic in the cubic phase, and, Mott insulator for x=0.875 and semiconductor for x=1 in the orthorhombic phase. The GdxBa1-xRuO3 alloy therefore undergoes a transition between a cubic phase and another orthorhombic at x = 0.5. It is clear that at this point our alloy (Gd0.5Ba0.5RuO3) is at the same time FM and AFM A-type, in another way, we can say that A-AFM and FM configurations coexist in our alloys. In the case of our GdxBa1-xRuO3 alloy, we can see that the total magnetic moment increases linearly with the concentrations "x" since it has passed from 15.99 μB for x = 0 to 39.95 μB for x = 0.5, this is valid in the cubic phase. That is related to a heavily magnetic moment of spin in the Ru atom which increases also linearly with increasing x, while the magnetic moment of Gd decreases slightly. In the orthorhombic phase, its value remains zero regardless of the concentration because we are in an antiferromagnetic (AF) configuration. The collaboration of the 3d-Ru and 2p-O states is suggested to play an important role for the ferromagnetism in the considered alloy. These orbitals were the most regular in the two bands respectively: the conduction band and the valence band in the two phases given here (cubic and orthorhombic). We also note the mixed collaboration of the states 3d-Ba. On the other hand, the contribution of 3d-Gd states was only effective in the band of conduction, at the time when that of the 4f-Gd states was noticed especially in the orthorhombic phase.

“…As shown in Figure 5A, an identical rise in electrical conductivity of both compounds has been observed, however, the rate of rise in electrical conductivity is faster in RbTaO 3 as compared to FrTaO 3 due to different rates of inner band transitions in the studied compounds. The electrical conductivity ( σ / τ ) of RbTaO 3 (7.050 × 10 20 (Ω. m. s) −1 ) is 2.5 times larger than σ / τ of FrTaO 3 (2.770 × 10 20 (Ω. m. s) −1 ) at the same temperature of 800 K. The escalation of the electrical conductivity at higher temperature might be associated with an increase in the Seebeck coefficient at similar range of temperature 48 . It is worth notable from DOS plots that in RbTaO 3 perovskite oxide, the dominant role in the conduction process is played by the electrons of Ta‐ d states along with O‐ p state charge carriers, but almost no contribution of charge carriers associated with Rb atoms that is why, RbTaO 3 appears to exhibit relatively high electrical conductivity.…”

Section: Resultsmentioning

confidence: 91%

“…The electrical conductivity (σ/τ) of RbTaO 3 (7.050 × 10 20 (Ω. m. s) −1 ) is 2.5 times larger than σ/τ of FrTaO 3 (2.770 × 10 20 (Ω. m. s) −1 ) at the same temperature of 800 K. The escalation of the electrical conductivity at higher temperature might be associated with an increase in the Seebeck coefficient at similar range of temperature. 48 It is worth notable from DOS plots that in RbTaO 3 perovskite oxide, the dominant role in the conduction process is played by the electrons of Ta-d states along with O-p state charge carriers, but almost no contribution of charge carriers associated with Rb atoms that is why, RbTaO 3 appears to exhibit relatively high electrical conductivity. However, in the case of FrTaO 3 perovskite oxide, electrons from 6p states of Fr, which show significant contribution to form VBM, contribute significantly in the charge transport and minimize the contribution of charge carriers from Ta-d and O-p states, consequently reducing the transport of charge and hence the conductivity as compared to that noticed in RbTaO 3 perovskite oxide.…”

Section: Thermoelectric Propertiesmentioning

confidence: 99%

DFT ‐based insight into the magnetic and thermoelectric characteristics of XTaO ₃ (X = Rb, Fr) ternary perovskite oxides for optoelectronic applications

et al. 2020

Summary Nowadays, there exists an increasing trend of investigating ternary perovskite oxide materials because of their wide applications in solar cells and similar electronic and optoelectronic devices. This work describes a systematic study performed through state‐of‐the‐art ab initio density functional theory (DFT) approach associated with the magnetic, electronic, and thermoelectric behavior of XTaO3 (X = alkali metals i.e., Rb, Fr) tantalate perovskite oxides. These compounds are found to be semiconductor because both materials have shown significant values of the band gap energy, that is, indirect energy band gap of 1.12 eV (↑↓) in RbTaO3 and direct band gap of 1.08 eV (↑↓) in FrTaO3. The calculated formation energies appear to be decreasing such as −3.54 and −1.92 eV for RbTaO3 and FrTaO3, respectively. The analysis through projected density of states discloses that Fr‐6p and 2p states from anion sites have shown overall contribution in forming the highest edge of the valence band (VBM), while, Ta‐5d states have depicted chief role to form major part of the conduction band minima, thereby, contributing in electronic conductivity. The much better values of thermoelectric parameters such as power factor of (5.5062 × 1013 W.m−1.K−2.s−1) and figure of merit (0.82) demonstrate that RbTaO3 is more dominating and promising semiconducting material which would, comparatively, be deemed an appropriate candidate for application in developing efficient thermoelectric devices. Finally, on the bases of above cited facts and the already existing data on similar perovskite oxides, it can be speculated that the studied compounds seem potential candidates to understand underlying physics and for possible applications in thermoelectric and other allied devices.