ABSTRACT
We introduce Na2[Fe3S4], comprising anionic layers, synthesized by a simple and straightforward solid-state method based on the fusion of binary sulfides of abundant sodium and iron. The structure crystallizes in a trigonal lattice with honeycomb cavities, as well as 25% of statistical iron vacancies in the crystal structure. The compound depicts high dielectric constants from 998 to 1850 at a frequency of 1 kHz depending on the sintering temperature, comparable with benchmark dielectric materials. According to the complex electrochemical impedance results, the compound depicts an electrical conductivity at ambient temperature. Optical investigations reveal a band gap of 1.64 eV, which is in agreement with an electronic band gap of 1.63 eV computed by density functional theory calculations. Magnetometry results reveal an antiferromagnetic behavior with a transition at 120 K. These findings introduce Na2[Fe3S4] as a sustainable multifunctional material with potential for a variety of electronic and magnetic applications.
ABSTRACT
High yields of phase-pure K3[Fe2S4] are obtained using a fast, straight-forward, and efficient synthetic technique starting from the binary precursors K2S and FeS, and elemental sulphur. The compound indicates soft ferrimagnetic characteristics with magnetization of 15.23 A m2 kg-1 at 300 K due to the mixed valence of FeII/FeIII. Sintering at different temperatures allows the manipulation of the microstructure as well as the ratio of grains to grain boundaries. This results in a variation of dielectric and impedance properties. Samples sintered at 923 K demonstrate a dielectric constant (κ) of around 1750 at 1 kHz, which lies within the range of well-known high-κ dielectric materials, and an ionic conductivity of 4 × 10-2 mS cm-1 at room temperature. The compound has an optical band gap of around 2.0 eV, in agreement with tailored quantum chemical calculations. These results highlight its potential as a material comprising non-toxic and abundant elements for electronic and magnetic applications.
ABSTRACT
The crystal structure of gold(II) sulfate is strikingly different from other coinage metal(II) sulfates. Central to the unsual AuSO4 bulk structure is the Au24+ ion with a very close Au-Au contact, which is a structural feature that does not appear in CuSO4 and AgSO4. To shed some light on this unusual behavior, we decided to investigate the relative stabilities of the coinage metal(II) sulfates utilizing periodic Density Functional Theory. By computing relative energies of the hypothetical nonrelativistic gold(II) sulfate (AuNRSO4) in different structural arrangements and performing chemical bonding analyses employing the Electron Localization Function as well as the Quantum Theory of Atoms in Molecules method, we show that the stability of the unsual AuSO4 bulk structure can be related to aurophilic interactions enabled by relativistic effects. From the relative stabilities and UV-vis spectra computed via GW methodology, we predict that AuNRSO4 would assume the structure of either copper(II) sulfate or silver(II) sulfate with almost equal likelihood and appear as bright-violet or deep-blue substances, respectively.
ABSTRACT
The ternary sulfido bismuthate K3[BiS3] is synthesized in quantitative yields. The material exhibits nonlinear optical properties with strong second harmonic generation properties at arbitrary wavelengths in the infrared spectral range and a notable laser-induced damage threshold of 5.22 GW cm-2 for pulsed laser radiation at a wavelength of 1040 nm, a pulse duration of 180 fs, and a repetition rate of 12.5 kHz. K3[BiS3] indicates semiconductivity with a direct optical band gap of 2.51 eV. Dielectric and impedance characterizations demonstrate κ values in the range of 6-13 at 1 kHz and a high electrical resistivity. A strong diamagnetic behavior with a susceptibility of -2.73 × 10-4 m3 kg-1 at room temperature is observed. These results suggest it is a promising nonlinear optical candidate for the infrared region. The synergic physical characteristics of K3[BiS3] provide insight into the correlation of optical, electrical, and magnetic properties.
