Pnictogen-based Zintl compounds have fascinating properties. Nowadays these compounds have gained exceptional interest in thermoelectric and optoelectronic fields. Therefore, in this work the ...structural, electronic and optical properties of SrZn
Pn
(Pn=N, P, As, Sb, Bi) compounds were studied using state-of-the-art density functional theory. The optimised lattice parameters (
,
,
and bond lengths) are consistent with the experimental results. The bulk moduli and
showed a decrease when changing the Pnictogen (Pn) anion from N to Bi in SrZn
Pn
(Pn=N, P, As, Sb, Bi). The modified Becke-Johnson potential is used for band structure calculations. All compounds show semiconducting behaviour except SrZn
Bi
, which is metallic. Pn-
, Zn-
and Sr-
play an important role in defining the electronic structure of the compounds. The optical conductivity and absorption coefficient strength are high in visible and ultraviolet regions. These band structures and optical properties clearly show that SrZn
Pn
compounds are potential candidates in the fields of optoelectronic and photonic devices.
Strontium-based Zintl materials SrCd2Pn2 (Pn = P/As) have been investigated here for their thermoelectric applications. The fundamental structural, optoelectronics and transport properties of Zintl ...SrCd2Pn2 (Pn = P/As) compounds were determined by employing the full potential linearized augmented plane wave approach (FP-LAPW). The formation and dynamical stabilities have been confirmed by formation energy and phonon dispersion studies. The established band structures using the modified Becke–Johnson potential (mBJ) reveals a direct energy bandgap (Eg) of 1.58 eV and 1.15 eV for SrCd2P2 and SrCd2As2, respectively. The DOS spectra disclose Pn(P/As) states are present in the valence band while Sr states are present in the conduction band. The optical features of the compounds were analyzed from dielectric constants, refractive index, extinction coefficient, and energy loss function against photon energy (eV) up to 30 eV. We observed that the material absorption by falling the light is fascinating in the visible region, revealing a viable choice for optoelectronics application. We evaluated transport properties like the Seebeck coefficient, electrical and thermal conductivity, power factor versus temperature, carrier concentration, and chemical potential with the classical Boltzmann transport theory. The computed Seebeck coefficients for SrCd2P2 and SrCd2As2 are found to be equal to 242μVK−1 and 239 μVK−1 at 300 K and 255 μVK−1, 257 μVK−1at 1200 K. The highest values of the power factor obtained at 1200 K are 5.88 × 1011 W/K2m.s, 5.21 × 1011W/K2m.s for SrCd2P2 and SrCd2As2, respectively. The tremendous optoelectronic characteristic and outstanding power factor values predicted this group could be favorable for uses in solar and thermoelectric uses.
The structural properties of SrCd22Pn (Pn=P/As) compounds were examined, and it was established that they have a trigonal crystal structure (P-3m1). Phonon investigations provide information about their dynamical stability. The SrCd22Y2(YP/As) compounds under investigation have a high figure of merit (ZT), which suggests their usage in thermoelectric devices. Display omitted
•Some physical properties of Zintl compounds SrCd22Pn (Pn=P/As) are investigated.•The SrCd2P2 and SrCd2As2 compounds are direct band gap semiconductors.•The vibrational properties reveal the dynamical stability of the compounds.•The large power factor for both compounds suggest that they are potential candidates for thermoelectric applications.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The structural, electronic, optical and thermoelectric properties of ternary CaMg2X2 (X = N, P, As, Sb and Bi) compounds are investigated using all electrons full potential linearized augment plane ...wave method. By using generalized gradient approximation (GGA), unit cell volumes of the compounds are optimized. For calculations of optical and electronic properties the modified Becke Johnson exchange potential is used along with the GGA. The direct energy band gap decreases by replacing the pnictogen elements, while indirect bandgap also decreases except for CaMg2As2. The optical properties show a prominent variation over the change of anion from N to Bi. There is inverse variation between refractive index and the band gap. The refractive indices of these compounds are high in the visible region and sharply decreased in the ultraviolet region. The thermoelectric properties are also studied using Boltzmann statistics through BoltzTrap code. A positive non-zero value of Seebeck coefficient shows a P-type semiconducting behavior of these compounds. High figure of merits (ZT) and optical conductivity peaks for all compounds reveal that they are good candidates for the thermo-electric and optoelectronics devices.
•CaMg2X2 (X = N, P, As, Sb and Bi) compounds are studied by FP-LAPW + lo method.•Major part is played by X-p state and Ca-d states in the valence/conduction bands.•Mixed covalent and ionic-like character bonding observed.•There is an inverse variation between refractive index and energy band gap.•A positive value of Seebeck coefficient shows these as P-type semiconductors.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Abstract
The structural, electronic, optical and thermoelectric properties of ternary CaBe
2
X
2
(X = N, P, As, Sb and Bi) have been investigated comprehensively for the first time using density ...functional theory. All the compounds are optimized to obtain their ground states. Computed structural parameters agree to the available experimental results. Electronic band structure calculations reveal the semiconducting nature of the compounds, while bang gap decreases by changing the anion X from N to Bi the band gap decreases. In the valence band, major contribution is due to X-
p
state, while in conduction band (CB) the major contribution is mainly due to the Ca-
d
state. Furthermore, electron charge density plots reveal ionic bonding character with small covalent bonding. Optical properties are calculated in detail. Static value of refractive index shows inverse variation with band gap. The refractive indices of these compounds are high in the infrared region and gradually decreased in the visible and ultraviolet region. The thermoelectric properties are studied using Boltzmann statistics through BoltzTraP code. High optical conductivity peaks and figure of merits (ZT) for compounds reveal that they are good candidates for the optoelectronics and thermo-electric devices.
The structural parameters, optoelectronic and thermoelectric properties of SrCd2X2 (X = P, As, Sb and Bi) compounds have been investigated thoroughly for the first time using first principles ...methods. The compounds are optimized and obtained structural parameters agree to the experimental data. Electronic band profiles of the compounds reveal that the SrCd2P2, SrCd2As2, SrCd2Sb are direct band gap semiconductors while SrCd2Bi2 is metallic. Valence band is composed on mainly X-p states while Sr-d state in conduction band. Compounds show the strong absorption in the visible region and low frequency ultraviolet region. The characteristics optical peaks shift towards lower energy by replacing the anion from P to Bi. Boltzmann transport theory is implemented through the BoltzTraP code to calculate the electrical and thermal conductivities, Seebeck coefficients and thermo power factor. High absorption peaks and figure of merits of the compounds show that these compounds can be important for optoelectronics and thermo-electric devices.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The emerging class of topological materials provides a platform to engineer exotic electronic structures for a variety of applications. As complex band structures and Fermi surfaces can directly ...benefit thermoelectric performance it is important to identify the role of featured topological bands in thermoelectrics particularly when there are coexisting classic regular bands. In this work, the contribution of Dirac bands to thermoelectric performance and their ability to concurrently achieve large thermopower and low resistivity in novel semimetals is investigated. By examining the YbMnSb2 nodal line semimetal as an example, the Dirac bands appear to provide a low resistivity along the direction in which they are highly dispersive. Moreover, because of the regular‐band‐provided density of states, a large Seebeck coefficient over 160 µV K−1 at 300 K is achieved in both directions, which is very high for a semimetal with high carrier concentration. The combined highly dispersive Dirac and regular bands lead to ten times increase in power factor, reaching a value of 2.1 mW m−1 K−2 at 300 K. The present work highlights the potential of such novel semimetals for unusual electronic transport properties and guides strategies towards high thermoelectric performance.
Single crystals of the YbMnSb2 nodal line semimetal demonstrate the synergetic contribution of Dirac bands and regular band to the thermoelectric performance. A high power factor over 2.1 mW m−1 K−2 is achieved due to both high mobility and large thermopower.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
DFT prediction of the structural, electronic, thermoelectric and optical properties of ternary pnictides MgBe2X2 (X = N, P, As, Sb and Bi) are investigated by using the all electron full potential ...linearized augment plane wave method. Geometrical optimization is carried out using the generalized gradient approximation (GGA). The exchange potential modified Becke Johnson (mBJ) along with the GGA is used to calculate the electronic and optical properties. MgBe2Sb2 and MgBe2Bi2 show semi-metallic nature whereas the rest of the compounds are semiconducting. The dielectric function, optical conductivity, reflectivity, and optical conductivity are calculated. The static value of the reflectivity R(0) and energy band gap (Eg) vary inversely to each other. The thermoelectric properties such as electrical conductivity, thermal conductivity, Seebeck coefficient and ZT are also studied by practicing Boltzmann statistics through Boltztrap code. MgBe2Bi2 has among the compound highest electrical conductivity at high temperature. The (N, P and As) based compounds are P-type while (Sb and Bi) based compound are N-type thermoelectric materials. High optical and thermal response for all compounds reveals that they are potential candidates for thermoelectric devices.
•MgBe2X2 (X = N, P, As, Sb and Bi) compounds are studied by FP-LAPW + lo method.•Major part is played by X-p state and Be-p states in the valence/conduction bands.•Mixed covalent and ionic-like character bonding observed.•Optical peaks shifted towards lower energy by changing the anions from N to Bi.•These materials have efficient thermoelectric properties.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Mg3Sb2-based compounds by virtue of nontoxicity and low-cost have become a promising class of candidates for midtemperature thermoelectric power generation. Here, we successfully fabricated n-type ...Mg3Sb2-based materials using an inexpensive and efficient approach of one-step ball milling and spark plasma sintering, and demonstrate that a complementary and favorable effect of multiple elements coalloying/-doping leads to an excellent thermoelectric performance. The intrinsic p-type conducting behavior for Mg3Sb2 could be changed to n-type through Bi and Se coalloying on Sb sublattices with excess Mg, resulting from the suppression of Mg vacancies and the formation of Mg interstitial. Furthermore, Mn doping on Mg sublattices could soften the chemical bonds, leading to the increase of carrier mobility and concentration simultaneously. Additionally, multielement coalloying/-doping could significantly increase the lattice disorder, which undoubtedly strengthens the phonon scattering and readily results in a suppressed lattice thermal conductivity. As a result, a highest ZT value of 1.6 at 723 K and an average ZT value up to 1.1 were obtained in the temperature range of 323–723 K in the Mg3.18Mn0.02Sb1.5Bi0.49Se0.01 sample, which is one of the highest values among the Te free Mg3Sb2. This work could give guidance for improving the thermoelectric performance of Zintl phase materials or even others using the multielement codoping/-alloying strategy.
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