Ab-initio study of half-metallic ferromagnetism and transport characteristics of MgV2S/Se4 spinels for spintronics and thermoelectric applications

First principles investigations of electronics, magnetic, and thermoelectric properties of rare earth based PrYO3(Y=Cr, V) perovskites

Physical features of transition metal (TM) doped lead selenide, Pb1-xCrxSe, Pb1-xCoxSe and Pb1-xNixSe (x=0% and 25%) have been investigated by ab-inito method. The exchange correlation energy is computed by generalized gradient approximation (GGA). A direct band gap (Eg) of 0.35 eV has been observed for PbSe. The analysis of spin-resolved electronic band structure (BS) and density of states (DOS) reveal the half-metallic ferromagnetic (HMF) character of doped compounds. In addition, the calculated magnetic moments (μB) of Pb1-xCrxSe, Pb1-xCoxSe and Pb1-xNixSe compounds are found to arise due to doped transition metals and confirmed by 3D spin-polaized iso-surface density plots. The optical features including optical conductivity (), absorption coefficient, extinction coefficient k, refractivity R, dielectric function and refractive index n() have been calculated to envisage the optical response of given materials. Further, the BoltzTrap code has been implemented to probe the thermoelectric characteristics in term of power factor (PF), Seebeck coefficient (S), thermal and electrical conductivity. The outcomes of calculations divulge that Pb1-xXxSe (X=Cr, Co, Ni) would be suitable candidates for both optoelectronics and thermoelectric applications.

Half-metallic semiconductors typically exhibit 100% spin polarization at the Fermi level which makes them desired materials for spintronic applications. In this study, we reported a half-metallic ferromagnetic nature in vacancy-ordered double perovskites Tl2WX6 (X = Cl and Br). The magnetic, electronic, and thermoelectric properties of the material are studied by the use of density functional theory (DFT). For the calculations of exchange-correlation potential, PBE-sol is employed while more accurate electronic band structure and density of states (DOS) are calculated by the mBJ potential. Both materials exhibited structural stability in the cubic structure with Fm3̄m space-group. The mechanical stability is confirmed by their computed elastic constants while their thermodynamic stability is attested by negative formation energy. The spin-based volume optimization suggested the ferromagnetic nature of the materials which is further confirmed by the negative value of the exchange energy Δ x(pd). Moreover, computed magnetic moment value for Tl2WCl6 and Tl2WBr6 is 2 μB and the majority of this comes from W. The spin-polarized band structure and DOS confirmed that both materials are half-metallic and at the Fermi level they exhibit 100% spin polarization. Furthermore, in the spin-down state, materials behave as semiconductors with wide bandgaps. Lastly, the thermoelectric properties are evaluated by the BoltzTrap code. The thermoelectric parameters which include the Seebeck coefficient, electrical conductivity, thermal conductivity, power factor, and figure of merit (ZT) are investigated in the range of temperatures from 200 to 800 K. The half-metallic ferromagnetic and thermoelectric characteristics make these materials desired for spintronics and thermoelectric applications.

Rare earth based Mg- chalcogenides MgDy2(S/Se)4 as an emerging aspirant for spintronic and thermoelectric applications

The narrow band bap double perovskites X2CuInCl6 (X = K, Rb, Cs) for optoelectronics, and thermoelectric applications

As two pivotal functional segments, triazine and porphyrin can be coupled to form a highly cross-linked conjugated polymer. Although the obtained conjugated polymers are almost insoluble in most so...

Advanced materials for heat energy transfer, conversion, storage and utilization, are very much at the forefront of academic and industrial interest. Within this context, we are delighted to provide cutting-edge insight into the emerging materials that promote the utilization of heat energy, via a special issue with a selection of 19 review and original research articles. These papers summarize the recent advances in thermoelectric materials, phononic metamaterials, thermal interfacial materials, nanomaterials, and the applications in thermal management and renewable energy. Thermoelectric materials are important for renewable energy technology. The thermoelectric performance is determined by the Seebeck coefficient, electrical conductivity, and thermal conductivity. The strong interaction between the different heat carriers, including phonons and electrons, complicates the optimization of thermoelectric efficiency. Yu et al. (article number 1904862) contribute a review paper that helps us understand the outstanding thermoelectric performance of main-group chalcogenides from a chemical bonding perspective. It is suggested that large valley degeneracy, band convergence, and high band anisotropy can result in high power factors. Moreover, compared to covalent and ionic bonds, the bonds in main-group chalcogenides are soft, causing large anharmonicity and low thermal conductivity. Zhao et al. (article number 1903867) present the recent advances in the structure and properties of liquid-like thermoelectrics, focusing on their unusual electron and phonon transport behaviors. Commonly adopted strategies for further improving the thermoelectric properties are also summarized. In addition to inorganic thermoelectric materials, bio-friendly organic thermoelectric materials are becoming promising candidates for thermoelectric devices. Zeng et al. (article number 1903873) introduce important advances in the experimental and theoretical studies of organic thermoelectric materials, including molecular junctions, organic-inorganic heterojunctions, and single-molecule magnet. Various optimization strategies for organic thermoelectric devices are discussed. In an independent review article, Wang et al. (article number 1904534) provide a survey of recent advances and emerging experimental and theoretical methodologies in probing and tuning thermal and thermoelectric transport in molecular junctions. Amorphous materials have valuable applications in thermoelectrics, thermal protection, flexible electronics, and artificial intelligence chips. Zhou et al. (article number 1903829) systematically review the fundamental physical aspects of thermal conductivity in amorphous materials and discussed a number of open problems. Shin et al. (article number 1904815) review the state-of-the-art of high temperature thermal materials used in thermal barrier coating, including dense materials and porous materials. In addition to a comprehensive list of high temperature thermal materials, the unique mechanisms governing thermal transport processes at high temperatures are also elucidated. Composites based on phase change materials have received tremendous attention due to their application in thermal energy storage and management. Yuan et al. (article number 1904228) systematically introduce the methods to manipulate the thermal conductivity of phase change materials. Considering the importance of conductive polymers and their composites in smart devices such as touch screen displays, health monitoring sensors, and functional clothing, Xu et al. (article number 1904704) provide a comprehensive summary of the thermal properties of conductive polymers. The fundamental thermal transport mechanisms, up-to-date advancements in regulating their thermal conductivity and thermal-related applications are addressed. The technology of phononic crystal provides a strategy for controlling the thermal conductivity of solids, with applications in new information technology, thermal management, and thermoelectrics. Sledzinska et al. (article number 1904434) provide a systematic review of the recent experimental achievements in the fabrication of phononic crystals and their applications in thermal management. Hussein et al. (article number 1906718) introduce the new emerging concept of nanophononic metamaterials, and provide a comprehensive comparison with nanophononic crystals. Although thermal conductivity reduction can be achieved in both, the underlying mechanism is different. Graphene has ultrahigh thermal conductivity, which is expected to be utilized in the thermal management of nanoscale electronic devices. More interesting, by coupling different physical quantities, graphene is also demonstrated in other applications, such as thermoacoustic coupling devices, thermoelectric coupling devices, and thermooptical coupling devices. Li et al. (article number 1903888) provide a review of the recent progress in graphene-based thermal devices. Although graphene has attracted a lot of attention in thermal management owing to its ultrahigh thermal conductivity, the thermal conductivity of graphene-based composites still needs to be improved. Barani et al. (article number 1904008) demonstrate remarkable enhancement in the thermal conductivity of the epoxy-based hybrid composites with graphene and Cu-NP fillers, whose effect is attributed to the formation of highly thermally conductive percolation networks. On the other hand, with the number of interfaces increasing, interfacial thermal resistance is becoming even more important than the channel material itself. Giri and Hopkins (article number 1903857) summarize the recent experimental and computational advances in thermal transport across solid/solid interfaces. The role of localized vibrational modes is also clarified. Meng and Wang (article number 1904796) introduce the development of antiscaling interfacial materials towards highly efficient heat energy transfer and discuss the various effects on thermal conductivity such as surface energy, surface roughness, and surface wettability. Since the first discovery of graphene, two dimensional (2D) materials opened up numerous competitive applications because of their unique and highly tunable physical and chemical properties. Zhao et al. (article number 1903929) provide a thorough understanding of the thermal transport properties of various 2D semiconductors, including transition metal dichalcogenides, black phosphorus, and SnSe. The phonon-governed applications, including thermoelectric power generation and photoelectric and thermal devices, are also addressed. The thermal properties of borophene are summarized by Li et al. (article number 1904349). Zhan et al. (article number 1903841) summarize the thermal properties of different 3D nanostructures ranging from 3D nanoarchitectures to metal–matrix composites, which are constructed from different nanomaterials including nanoparticles, nanotubes, nanowires, nanoribbons, and nanosheets. In recent years, one emerging concept in physics is “topological phononics.” Using 2D materials as examples, Liu et al. (article number 1904784) introduce the novel concepts of Berry phase, topology, and pseudospin for phonons. The corresponding phenomena in one- and three-dimensional systems are also covered. Another important feature in terms of the thermal properties of 2D materials is the unusually high heat radiation. Although the amount of heat energy carried by radiation is usually lower than that through conduction, a significant enhancement of five orders of magnitude are demonstrated in 2D materials, contributed by the hyperbolic electromagnetic dispersion. Baudin et al. (article number 1904783) discuss the possibility of radiation cooling in 2D materials, focusing on the graphene and hexagonal boron nitride heterostructures. They introduce the concepts and mechanism of super-Planckian thermal emission and electroluminescent cooling. In conclusion, we would like to thank the authors for providing their important contributions to this special issue. We greatly appreciate Dr. Huan Wang for organizing this special issue, as well as the whole editorial team of Advanced Functional Materials, for their great support and kind cooperation. We sincerely hope that the readers of Advanced Functional Materials will enjoy reading this special issue.

Physical properties of half-metallic AMnO3 (A = Mg, Ca) oxides via ab initio calculations

A computational study for mechanical, thermoelectric and optoelectronic applications of BiAlO3 under static pressure

Magnetic spinel oxides LiZ2O4 (Z = Mn, Fe, Co, and Ni) have recently appealed the scientific community due to their interesting magnetic and thermoelectric applications. In the current article, the electronic, magnetic, and thermoelectric properties of LZO have been elaborated using density functional theory-based Wien2k code. The band structures and total density of states ensure the half metallic ferromagnetic (HMF) nature of the studied compounds. Furthermore, the magnetism is discussed in detail using crystal field, John-Teller, and exchange energies involved in the system and spin density. Finally, electrical conductivity, thermal conductivity, power factor, Seebeck coefficient, and thermal efficiency computed by using BoltztraP code suggest these compounds for thermoelectric device fabrications.

Here, we present our current attempt to intrinsically dope Ni0, Co0, and Fe0 nanoparticles within NiII‐, CoII‐, and FeII‐borate glassy matrices, respectively. The system was prepared by one‐pot reaction of the desired MTII salt with excess NaBH4 through an in‐situ reduction and hydrolysis processes to afford metallic MT0 nanoparticles dispersed into the MT‐BO3 matrix. The composition and structural characteristics of these MT0:MT‐BO3 materials were identified by thermal oxidation, ATR‐IR, X‐ray powder diffraction, and magnetic techniques as glassy/amorphous borate matrices containing magnetic nanoparticles. The electrical conductivity (σ) of cold‐pressed discs of these metal‐doped composites shows that they behave as nonohmic semiconductors within the temperature range of 303 ≤ T ≤ 373 K suggesting a mixed electronic‐ionic conduction. However, their thermal conductivity (κ) occurs through phonon lattice vibration dynamics rather than electronic. The σ/κ ratio shows a steep non‐linear increase from 9.4 to 270 KV−2 in Ni0:Ni‐BO3. In contrast, a moderate‐weak increase is observed for Co0:Co‐BO3 and Fe0:Fe‐BO3 analogs. The obtained materials are examined for thermoelectric (TE) applications by determining their Seebeck coefficient (S) power factor (PF), figure of merit (ZT), and conversion efficiency (η%). All the TE data shows that Ni0:Ni‐BO3 (S, 80 μVK−1; PF, 97.7 mWm−1 K−1; ZT 0.54; η, 2.15%) is a better TE semiconductor than the other two MT0:MT‐BO3. This finding shows that Ni0:Ni‐BO3 is a promising candidate to exploit low‐temperature waste heat from body heat, sunshine, and small domestic devices for small‐scale TE applications.

Structural stability, optoelectronic, thermoelectric, and elastic characteristics of X2ScBiO6 (X= Mg, Ca, and Ba) double perovskites for energy harvesting: First-principles analysis

The cubic Sr2XNbO6 (X = La, Lu) double perovskite oxides (DPOs) have been examined by density functional theory (DFT). Structural, elastic, electronic, thermoelectric (TE), and optical characteristics are computed by utilizing the full-potential linearized augmented plane wave method (FP-LAPW). It is probed that Sr2LaNbO6 and Sr2LuNbO6 are semiconductors with direct band gap (Eg) of 4.02 and 3.7 eV, respectively at theΓ symmetry points. To ensure the structure's stability, the Goldschmidt tolerance factor (τ) and the enthalpy of formation energy ( ∆E) are determined. Shear modulus (G), poisson's ratio (χ), elastic coefficient (Cij), anisotropy (A), bulk moduli (B), young's modulus (Y), and pughratio (B/G) are computed. Furthermore, thermoelectric (TE) features such as seebeck coefficient (S), figure of merit (ZT), electrical conductivity (σ), power factor (PF), and thermal conductivity (K) are determined by using BoltzTrap code. The estimated values of ZT reveal that Sr2LuNbO6 is a more promising material for TE applications. Optical characteristics such as absorption coefficient α(ω), dielectric constant ε(ω), optical conductivity σ(ω), refractive index n(ω), and reflectivity R(ω) are also calculated. Computation indicated that Sr2XNbO6 (X = La, Lu) are promising materials for TE and optoelectronics applications in the UV region.

Stable lead free double perovskites Cs2XAu(Br/I)6 (X = Y, Sc) as an emerging aspirant for solar cells and thermoelectric applications

Investigation of the electronic, magnetic, elastic, thermodynamic and thermoelectric properties of Mn2CoCr Heusler compound: A DFT-based simulation