Perovskite-like Framework Encapsulated with Fe-Based Magnetic Units in Ba₁₀Fe₃Sb₇Se₂₄

Abstract

Ba10Fe3Sb7Se24 was synthesized using a KBr flux at 850 °C (Crystal Data: orthorhombic, Cmc21, a = 9.3412(2) Å, b = 44.6666(10) Å, c = 12.5496(3) Å, V = 5236.2(2) Å3, and Z = 4). The compound adopts a new three-dimensional framework constructed by the layer to include Fe2Se6 dimers and FeSe4 tetrahedra in the linkage motifs of [Fe2SbSe10] and [FeSb6Se14], respectively. Alternatively, the all Sb-based polyhedra are assembled as a semiconducting, perovskite-like framework lacking an inversion center where these Fe-based magnetic units are trapped within the interstices. The strong antiferromagnetic interaction is revealed by a high Curie constant of −113 K, but the curvature of field-cooled and zero-field-cooled magnetic susceptibilities bifurcating at ∼19 K is observed. The critical temperature is well verified by a broad peak of χM″ signal showing a rapid increase below 19 K under an alternating current field. The Fe2Se6 dimer featuring distorted edge-sharing tetrahedra to induce the spin-canted antiferromagnetic ordering strongly dominates such magnetic ordering. Finally, a weak hysteresis loop is clearly observed at 2.0 K. This dilute magnetic selenide displays a direct bandgap at ∼1.54 eV, analyzed by the Tauc equation. Interestingly, the use of second-harmonic-generation temperature dependence shows a turning point at ∼20 ± 1 K, which precisely corresponds to the magnetic ordering temperature within the error bar, thereby demonstrating the versatility of the technique for probing magnetic phase transition.

Germanium Antimony Bonding in Ba4Ge2Sb2Te10 with Low Thermal Conductivity

“…Furthermore, the Sb 3+ /Bi 3+ centered coordination polyhedra of chalcogens (Q = S, Se, and Te) are often distorted since the ns 2 lone pair of electrons of Sb 3+ /Bi 3+ are susceptible to undergo the second-order Jahn–Teller (SOJT) distortions. As a result of flexible chalcogen polyhedra around Sb 3+ /Bi 3+ species, many new complex crystal structure types were discovered in the past few decades (e.g., CsBi 4 Te 6 , β-K 2 Bi 8 Se 13 , Ba 10 Fe 3 Sb 7 Se 24 , and Ba 4 SiSb 2 Se 11 ). Sn/Ge atoms in chalcogenides mainly exist in the +2 and +4 states (most stable) in contrast to Sb 3+ /Bi 3+ in the majority of the chalcogenides.…”

Preparation of Ti3+-TiO2 Supported Petroleum Pitch-Based Three-Dimensional Graphene Oxide Composite Photocatalysts for Photocatalysis of N2/H2O into Ammonia

“…It is suggested that one of reasons for the highest photocatalytic activity of 75%-Ti 3+ -TiO 2 @3D-GO is its highest visible light absorption intensity. In order to prove this result, we used the Tauc equation (eq 2) 45 to find the linear relationship between (αhν) 2 and hν using UV−vis data shown in Figure 6A. After obtaining the curve shown in Figure 6B, we made a tangent line intersecting the x-axis along the straight part of the curve and roughly obtained the band gap values of 75%-Ti 3+ -TiO 2 @3D-GO, 65%-Ti 3+ -TiO 2 @3D-GO, 85%-Ti 3+ -TiO 2 @3D-GO, and pure Ti 3+ -TiO 2 , and the values are 1.59, 1.73, 2.14, and 2.25 eV, respectively.…”