The First Mixed Calcium Zinc Borate with a Flexible [B₈O₁₇] Fundamental Building Block and Short UV Cutoff Edge

Abstract

The first mixed calcium zinc borate with a new fundamental building block (FBB) [B8O17], Ca1.13Zn0.87B8O14 has been successfully synthesized. It exhibits two independent interpenetrating three‐dimensional B−O anion networks constructed by [B8O17] groups, enriching the structural diversity of B−O configurations. In particular, the UV‐Vis‐NIR diffuse‐reflectance spectrum shows that it has a short UV cutoff edge (<195 nm).

Ba6Zn6(B3O6)6(B6O12): Barium Zinc Borate Contains π-Conjugated [B3O6]3– Anions and [B6O12]6– Anion with Edge-Sharing BO4 Tetrahedra

“…All six Zn 2+ atoms are tetrahedrally coordinated with Zn–O distances of ZnO 4 tetrahedra with bond lengths between 1.884(4) and 2.095(9) Å. These bond distances are consistent with other zincoborates reported previously. − …”

“…Recently, zincoborates have become a research hotspot as UV/DUV birefringent materials because the Zn 2+ cation with d 10 closed-shell electronic configurations can also have short UV cut-off edges . Meanwhile, due to the regulatory effect in arranging BO 3 groups, the ZnO 4 tetrahedra with considerably strong covalence are introduced into the borates to accelerate the formation of isolated B–O groups, which is extensively applied to adjust the arrangement of BO 3 groups. ,− By this way, some KBBF-like (KBBF as KBe 2 BO 3 F 2 ) zincoborates have adequate birefringence because the π-conjugated BO 3 groups are in optimally aligned configurations to produce large optical anisotropy and birefringence . Although some of the zincoborates reported, such as ZnB 4 O 6 F 2 (204.96 nm, 0.101@1064 nm), and CaZn 2 (BO 3 ) 2 (<190 nm, 0.081@546 nm), have excellent birefringence and can achieve UV transmission, most zincoborates are much smaller than β-BBO (0.113 at 1064 nm) (see in Table ).…”

“…Meanwhile, due to the regulatory effect in arranging BO 3 groups, the ZnO 4 tetrahedra with considerably strong covalence are introduced into the borates to accelerate the formation of isolated B–O groups, which is extensively applied to adjust the arrangement of BO 3 groups. ,− By this way, some KBBF-like (KBBF as KBe 2 BO 3 F 2 ) zincoborates have adequate birefringence because the π-conjugated BO 3 groups are in optimally aligned configurations to produce large optical anisotropy and birefringence . Although some of the zincoborates reported, such as ZnB 4 O 6 F 2 (204.96 nm, 0.101@1064 nm), and CaZn 2 (BO 3 ) 2 (<190 nm, 0.081@546 nm), have excellent birefringence and can achieve UV transmission, most zincoborates are much smaller than β-BBO (0.113 at 1064 nm) (see in Table ). − According to the anionic group theory, the number densities of π-conjugated BO 3 units have an equivalent effect on the optical properties. ,, In addition, the best parallel arrangement of the π-conjugate B–O units ([B 3 O 6 ] 3– and [B 6 O 12 ] 6– ) can make the maximum contribution to the optical anisotropy and birefringence.…”

“…Although some of the zincoborates reported, such as ZnB 4 O 6 F 2 (204.96 nm, 0.101@1064 nm), and CaZn 2 (BO 3 ) 2 (<190 nm, 0.081@546 nm), have excellent birefringence and can achieve UV transmission, most zincoborates are much smaller than β-BBO (0.113 at 1064 nm) (see in Table ). − According to the anionic group theory, the number densities of π-conjugated BO 3 units have an equivalent effect on the optical properties. ,, In addition, the best parallel arrangement of the π-conjugate B–O units ([B 3 O 6 ] 3– and [B 6 O 12 ] 6– ) can make the maximum contribution to the optical anisotropy and birefringence. Therefore, it is hoped that the zincoborates will have larger birefringence if we increase the densities of the π-conjugated BO 3 or B 3 O 6 groups in their structures and these groups are in parallel packing fashion.…”

Na2SrB16O26: a new borate with independent interpenetrating B–O networks and deep-ultraviolet cutoff edge

“…It is noticed that in the huge number of known borates, structures with independent interpenetrating networks are limited. Typical examples can be found in K 2 BaB 16 O 26 , 60 α-LiKB 8 O 13 37 and Ca 1.13 Zn 0.87 B 8 O 14 , 61 etc .…”