Thermodynamic Properties, Structure and Phase Stabilities of Special Alloys: Poster Session
Program Organizers: Erwin Povoden-Karadeniz, CDL-IPE TU Wien; Ernst Kozeschnik, Vienna University of Technology
Tuesday 10:00 AM
November 3, 2020
Room: Poster Hall
Location: MS&T Virtual
Funding support provided by: MatCalc Engineering GmbH, Vienna
Session Chair: Erwin Povoden-Karadeniz, TU Wien
Depiction of Electro-optical Characteristics in CdSexTe1-x by Curbing Content And Short-Range Pattern: Bishal Dumre1; Nathan Szymanski2; Vijaya Adhikari1; Indiras Khatri1; Daniel Gall3; Sanjay Khare1; 1The University of Toledo; 2University of California, Berkeley; 3Rensselaer Polytechnic Institute
We investigated CdSexTe1-x alloys in the zincblende and wurtzite structures deploying first principles methods. We developed phase diagram exploiting the cluster expansion prescription, where zincblende-to-wurtzite phase borderline is determined for Se congregation of x = 0.5-0.6, correspondingly, consolute temperature was obtained to be 325 K. Electro-optical characters for disordered CdSexTe1-x, whose crystallographic positions are represented utilizing special quasirandom structures, are calculated with the hybrid HSE06 functional. Downward bowing in the band gap and effective hole mass of the zincblende structure is culminated for its promising advantages in photovoltaics via improved net photocurrent. Zincblende CdSexTe1-x manifests potential benefits owing to considerable optical absorption throughout all Se concentrations. Finally, we report the existence of short-range order in CdSexTe1-x exhibited by clustering amidst similar atoms as a means to reduce strain. The intensity of clustering, which may be modulated by temperature, also influences the measure of the band gap.
Determination of the Activation Energy of the Formation of Intermetallic Compounds in the Ni-Al and Ti-Al System Upon Receipt of Special Alloys: Borys Sereda1; Dmytro Sereda1; Yuriy Belokon2; Ivan Babko1; 1Dneprovsky State Technical University; 2ZNU
In work the two methods for activation energy determination at the intermetallics formation are considered: theoretical calculation method based on the results of thermodynamic analysis during SHS-reactions and experimental method based on the study of the kinetics formation in intermetallic phases. It is established that the activation energies for the Ni-Al and Ti-Al systems are ~45 and ~82 kJ/mol respectively. It is shown that the difference between the values of activation energies obtained by two different methods does not exceed 5 %. The obtained results can be used for further calculations of reactions in the physicochemical model in intermetallide systems upon receipt of special alloys of the Ni-Al and Ti-Al systems formed under non-stationary temperature conditions.
Sodium Pnictogen Chalcogenides for Thermoelectric and Photovoltaic Applications: Ishan Khare1; Nathan Szymanski2; Daniel Gall3; Richard Irving1; 1Department of Physics and Astronomy, University of Toledo; 2Department of Materials Science and Engineering, University of California, Berkeley; 3Department of Materials Science and Engineering, Rensselaer Polytechnic Institute
We study the structural, electronic, optical, and thermoelectric properties of nine ternary chalcogenides, NaAX2, where A represents As, Sb, and Te, and X represents S, Se, and Te. Calculations based on density functional theory yield the following results: (i) phonon dispersion curves predict three of the compounds, NaAsS2, NaSbS2, and NaSbSe2, to be dynamically stable in the monoclinic, C2/c, structure, (ii) A-X electronic bonding features vary significantly with structural distortions arising from atomic size mismatch, therefore directly influencing stability, (iii) strong absorption is observed in the stable compounds, with coefficients ranging from 104 to 105 cm-1 in the visible-UV range, and (iv) remarkably high Seebeck coefficients exceeding 500 μV/K, at carrier concentrations commonly achieved in such materials, are found. From these results, we conclude that NaAsS2, NaSbS2, and NaSbSe2 are suitable candidates for both photovoltaic, particularly in tandem solar cells, and thermoelectric applications. Experimental synthesis and verification are suggested.