Cation Regulation to Investigate the Chalcogenide Borate RE₆Nb₂MgSB₈O₂₆ (RE = La–Nd) Family

Abstract

Chalcogenide borates have been developed and are considered an attractive system due to their favorable physical properties such as magnetism and nonlinear optical effects. Here, isostructural RE 6 Nb 2 MgSB 8 O 26 (RE = La−Nd) compounds in the title family have been obtained through cation regulation in rare-earth and VB group metals. This family crystalizes in the centrosymmetric P3̅ space group and features 3D frameworks formed by {[Mg(NbB 4 O 13 ) 2 ] 16− } ∞ polyanionic layers and QRE 6 octahedra. The structural chemistry was characterized and theoretical calculations were performed to understand the structural merit of this family. In addition, RE 6 Nb 2 MgSB 8 O 26 possess the largest band gaps among known rare-earth chalcogenide borates, and they all show antiferromagnetic-like behaviors.

Sharp Enhancement of Birefringence in Antimony Oxalates Achieved by the Cation–Anion Synergetic Interaction Strategy

“…30−32 At present, cations of alkali or alkaline earth metals are often introduced to explore new birefringent materials to ensure the transmittance in the ultraviolet band. 33 However, these two types of cations contribute little to birefringence and can hardly modulate structural dimensions as structure-directing agents. Therefore, the introduction of cationic functional units with large polarizability anisotropy, a high transmission in the UV region, and a strong structure-directing effect would induce further enhancement of the birefringence.…”

“…Among the birefringent materials reported so far, the birefringent functional groups almost just involved anionic groups, while the contribution of simple cations to birefringence is often neglected. − At present, cations of alkali or alkaline earth metals are often introduced to explore new birefringent materials to ensure the transmittance in the ultraviolet band . However, these two types of cations contribute little to birefringence and can hardly modulate structural dimensions as structure-directing agents.…”

Mixed Rare-Earth Chalcogenide Borate Eu9–xRExMgS2B20O41 (RE = Sm, Gd) Featuring a 3D {[B20O41]22–}∞ Framework Connected by [B6O9(O0.5)6]6– and [B7O13(O0.5)3]8– Clusters

“…Therefore, the band gap of 2 is primarily contributed by a charge jump between Eu 4f and Gd 5d orbits. The calculated Δ n ’s of 2 are 0.011 (1064 nm) and 0.013 (2100 nm) (Figure S11), and the value of 0.011 at 1064 nm is smaller than Gd 6 Ta 2 MgSeB 8 O 26 (0.047) and La 6 Nb 2 MgSB 8 O 26 (0.033), which have second-order Jahn-Teller (SOJT)-effective Ta 5+ /Nb 5+ d 0 cations in their structures leading to high structural distortion.…”

“…RE 3 S 3 BO 3 (RE = Sm, Gd) only have isolated planar triangles in the structure . In Eu 2 SB 5 O 9 /Eu 4.5 B 5 O 9 SI, RE 6 M 2 MgQB 8 O 26 (RE = La–Nd, Sm–Gd; M = Ta, Nb; Q = S, Se), and Cd 3 B 7 O 13 S 2 , there are isolated [B 5 O 9 ] 3– , [B 4 O 10 ] 8– , and [B 7 O 12 ] 3– clusters, respectively. The {[BO 2 ] − } ∞ chain in YSeBO 2 is obtained by connecting BO 3 units to each other through corner-sharing .…”

“…Combining these ions’ respective features, it is amazing and attractive to introduce them into one structure, which may show a special structure and interesting physical properties. Previously, several types of RE chalcogenide borates have been reported, including RE 3 S 3 BO 3 (RE = Sm, Gd), Eu 2 SB 5 O 9 , Eu 4.5 B 5 O 9 SI, YSeBO 2 , Eu 9 MgS 2 B 20 O 41 , and RE 6 M 2 MgQB 8 O 26 (RE = La–Nd, Sm–Gd; M = Ta, Nb; Q = S, Se) . All of them exhibit magnetic behaviors, and some are NLO actives.…”