Synthesis, Structure, and Properties of EuLnCuSe3 (Ln = Nd, Sm, Gd, Er)

Abstract

EuLnCuSe3 (Ln = Nd, Sm, Gd, Er), due to their complex composition, should be considered new materials with the ability to purposefully change the properties. Samples of the EuLnCuSe3 were prepared using Cu, rare earth metal, Se (99.99%) by the ampoule method. The samples were obtained by the crystallization from a melt and annealed at temperatures 1073 and 1273 K. The EuErCuSe3 crystal structure was established using the single-crystal particle. EuErCuSe3 crystallizes in the orthorhombic system, space group Cmcm, KCuZrS3 structure type, with cell parameters a = 4.0555 (3), b = 13.3570 (9), and c = 10.4602 (7) Å, V = 566.62 (6) Å3. In structure EuErCuSe3, erbium ions are coordinated by selenium ions in the octahedral polyhedron, copper ions are in the tetrahedral coordination, europium ions are between copper and erbium polyhedra layers and are coordinated by selenium ions as two-cap trigonal prisms. The optical band gap is 1.79 eV. At 4.7 K, a transition from the ferrimagnetic state to the paramagnetic state was detected in EuErCuSe3. At 85 and 293 K, the compound is in a paramagnetic state. According to XRPD data, EuLnCuSe3 (Ln = Nd, Sm, Gd) compounds have a Pnma orthorhombic space group of the Eu2CuS3 structure type. For EuSmCuSe3, a = 10.75704 (15) Å, b = 4.11120 (5) Å, c = 13.37778 (22) Å. In the series of EuLnCuSe3 compounds, the optical band gap increases 1.58 eV (Nd), 1.58 eV (Sm), 1.72 eV (Gd), 1.79 eV (Er), the microhardness of the 205 (Nd), 210 (Sm), 225 (Gd) 235 ± 4 HV (Er) phases increases, and the thermal stability of the phases increases significantly. According to the measurement data of differential scanning calorimetry, the EuNdCuSe3 decomposes, according to the solid-phase reaction T = 1296 K, ΔH = 8.2 ± 0.8 kJ/mol. EuSmCuSe3 melts incongruently T = 1449 K, ΔH = 18.8 ± 1.9 kJ/mol. For the EuGdCuSe3, two (Tα↔β = 1494 K, ΔHα↔β = 14.8 kJ/mol, Tβ↔γ = 1530 K, ΔHβ↔γ = 4.8 kJ/mol) and for EuErCuSe3 three polymorphic transitions (Tα↔β = 1561 K, ΔHα↔β = 30.3 kJ/mol, Tβ↔γ = 1579 K, ΔHβ↔γ = 4.4 kJ/mol, and Tγ↔δ = 1600 K, ΔHγ↔δ = 10.1 kJ/mol). The compounds melt incongruently at the temperature of 1588 K, ΔHmelt = 17.9 ± 1.8 kJ/mol and 1664 K, ΔHmelt = 25.6 ± 2.5 kJ/mol, respectively. Incongruent melting of the phases proceeds with the formation of a solid solution of EuSe and a liquid phase.

Electronic and optical properties of quaternary selenides for optoelectronic applications: Insights from DFT+U‐computations

“…The critical point that are situated between 0.5 and 2.0 eV for the investigated compounds corresponding to the optical transitions from the valance band maximum (Cu‐d state) to conduction band minimum (U/Gd/Zr‐d state) and is termed as the fundamental absorption edge. Our results shows good agreement with the previous work [9] as the optical transitions for CsGdZnSe 3 and BaGdCuSe 3 compounds occur at and 1.96 eV that are assumed from the diffuse reflectance spectra [19, 20].…”

Photodetecting properties on Sn-doped Bi2S3 thin film fabricated by nebulizer spray pyrolysis technique

“…The (αhυ) 2 versus photon energy (hυ) plots for all the produced Sn-doped Bi 2 S 3 samples are displayed in figure 3(b). The band gap values for Bi 2 S 3 thin films were calculated by extrapolating the linear fit from the slope up to the photon energy axis [45][46][47]. The bandgap value of the pure Bi 2 S 3 thin film was found to be 2.47 eV, which is in line with the reported optical results of the Bi 2 S 3 crystals by P. Makuła et al [42].…”

Optimization of Growth Parameters of the RF-Sputtered CuInGaSe2 Thin Films for Photovoltaic Applications

“…The energy bandgap can be estimated by the linear interpolation of the (αhυ)2 curve to the energy axis. 42,43 The estimated bandgap values of the samples deposited at RT, 200 °C, and 300 °C were 1.40, 1.22, and 1.18 eV. The obtained energy band gap values are reported to be optimal for producing high-efficiency thin-film solar-cell devices.…”