Thermodynamics of defect subsystem in zinc telluride crystals

In this work, the electrochemical behavior of LaMnO3 perovskite material and nanoporous carbon material in an aqueous solution of lithium sulfate are studied. The regularities of the expediency of the joint functioning of these materials as electrodes for a hybrid electrochemical capacitor are determined. It was found that the value of the specific capacity of the investigated electrochemical system of LaMnO3 / electrolyte / AC is 52 F/g during the discharge of the system to 1 V and the value of specific energy is 112.1 J /g at a discharge current of 1 mA.

Section: Resultsmentioning

confidence: 99%

Mechanisms of charge accumulation of the electrochemical system LaMnO3 / AC

Kolkovska

Rachiy

Kolkovskyi

et al. 2021

“…The compounds, in which structure cations of heavy atoms are located within the anionic sublattice of light atoms, can reveal interesting physical properties [22,23].…”

Section: Discussion Of Resultsmentioning

confidence: 99%

Crystal structure of chalcogenides R'xR''yR'''zPbSi2S8 (R' – La, R'' – Tb, R''' – Er)

Марчук

Smitiukh

Prots

et al. 2021

The chalcogenides LaxTbyErzPbSi2S8 were obtained by synthesizing the elementary components in vacuum quartz containers at 1320 K. The synthesized alloys were homogenized by annealing at 770 K during 500 hours. The cell parameters of synthesized sulfides are: a = 0,89576(3) nm, c = 2,65646(8) nm – La1,2Tb0,4Er0,4PbSi2S8; a = 0,89209(1) nm, c = 2,63466(5) nm – La0,9Tb0,2Er0,9PbSi2S8; a = 0,89002(3) nm, c = 2,62714(7) nm – La0,67Tb0,67Er0,67PbSi2S8; a = 0,88993(1) nm, c = 2,62973(4) nm – La0,6Tb1,2Er0,2PbSi2S8; a = 0,885161(7) nm, c = 2,60445(3) nm – La0,2Tb0,9Er0,9PbSi2S8 respectively. The atoms of statistical mixture (La,Tb,Er,Pb) occupy the site 18e (x y 1/4), and the atoms of Si occupy the site 12c (1/3 2/3 z) in the structure of the obtained chalcogenides. Coordinating polyhedra of atoms of the statistical mixture (La, Tb, Er, Pb) are trigonal prism with two additional atoms (CN = 8), and the atoms of Si occupying the crystallographic point system 12c describes with the tetrahedron. According to the results of the experiment, the synthesized chalcogenides crystallize in the structure type of La2PbSi2S8 (hR26,167). The structure of La2PbSi2S8 is described by using the theory of second anion coordination (SAC).

“…Quantum chemical (QC) calculations were performed using the Firefly QC program package [44], which is based on the GAMESS (US) source code [45]. The calculations were performed based on the hybrid functional B3LYP that used the Becke GGA functional for the exchange energy, and the Lee-Yang-Parr GGA functional for the correlation energy [46,47]. For the calculations, we employed lattice parameters, symmetry information, and atomic coordinates obtained during the crystal structure refinement of the Cu2CoHf3S8 and using literature data for CuCo2S4 and CuHf2S4 compounds.…”

Section: Methodsmentioning

confidence: 99%

Effect of the crystal structure and chemical bonding on the electronic and thermal transport in Cu2MeHf3S8 (Me – Mn, Fe, Co, Ni) thiospinels

Smitiukh¹,

Soroka²,

Марчук³

2023

Establishing the relationship between crystal structure and transport properties is an important issue that is directly connected with the applicability of functional materials. In this work, we present the analysis of the crystal structure, chemical bonding, and electronic and thermal transport properties of Cu2МеHf3S8 (Ме – Mn, Fe, Co, Ni) compounds. The increase of weighted mobility in the Mn → Fe → Со → Ni series as well as the change of the dominant scattering mechanism of charge carriers from scattering on point defects to the scattering on acoustic phonons explains the best electronic transport in Cu2NiHf3S8. Moreover, bonding inhomogeneity between the covalent δ(Co – S) and δ(Hf – S) from one side, and more ionic δ(Cu – S) interactions from the other side leads to low lattice thermal conductivity in Cu2MeHf3S8 (Me – Mn, Fe, Co, Ni) materials. The work also suggests the link between the occupation of the octahedral 16d site and the thermoelectric performance of the investigated thiospinels. Particularly, the best thermoelectric performance is observed in the case of the presence of two valence electrons in the d-level of atoms in octahedral voids, which can be essential for further enhancement of the thermoelectric performance in thiospinels.