Deep‐Ultraviolet Nonlinear Optical Crystal Cs₂Al₂(B₃O₆)₂O: A Benign Member of the Sr₂Be₂(BO₃)₂O Family with [Al₂(B₃O₆)₂O]²⁻ Double Layers

Abstract

For the explorations of deep ultraviolet (DUV) nonlinear optical (NLO) borates, a type of important optoelectronic material, the (BO ) group has been long regarded as the sole microscopic optically-active unit, and toxic Be-containing raw materials are frequently-adopted. Herein, a new DUV NLO crystal, Cs Al (B O ) O (CABO), was designed and synthesized by simultaneously replacing the (BO ) groups and Be cations for (B O ) units and Al cations in Sr Be (BO ) O, which possesses a favorable structure, through a chemical co-substitution approach. CABO exhibits a considerable DUV NLO capability because of the wide band gap and large birefringence originating from the [Al (B O ) O] double layers. Remarkably, CABO melts congruently and does not contain the toxic beryllium, which is favorable for bulk-size crystal growth and practical applications.

CsAlB3O6F: a beryllium-free deep-ultraviolet nonlinear optical material with enhanced thermal stability

“…DFT calculations of the band gap using the HSE06 hybrid functional with high accuracy result in 7.49 eV (corresponding to 166 nm), further indicating that CABF could be an excellent candidate for optical materials operating in the DUV region. As described earlier, 26,28 the large band gap of CABF could be attributed to the elimination of dangling bonds in [B 3 O 6 ] units and the introduction of uorine.…”

Li2BaSc(BO3)2F and LiBa2Pb(BO3)2F with Layered Structures featuring Special Li−O/F Configurations

“…So far, using MO 4 or MO 3 F (M=Li, Zn, Al, and Ga, etc.) tetrahedra to substitute the BeO 4 tetrahedra in 2 ∞ [Be 2 BO 3 F 2 ] layers of KBBF is considered to be an effective design tactic to make structural modifications, which may inherit the benign BO 3 arrangement of KBBF, just like “DNA” in biology . The strategy has afforded many new functional materials with KBBF‐type structures and good properties, for instance, Cs 3 Zn 6 B 9 O 21 , K 2 Al 2 B 2 O 7 , and the A 3 B 3 Li 2 M 4 B 6 O 20 F (A=K, Rb; B=Ba, Sr; M=Al, Ga) series, etc.…”

“…) tetrahedra to substitute the BeO 4 tetrahedra in 2 1 [Be 2 BO 3 F 2 ]l ayers of KBBF is considered to be an effective design tactic to make structural modifications, whichm ay inherit the benign BO 3 arrangement of KBBF,j ust like "DNA" in biology. [15][16][17][18][19] The strategy has afforded many new functional materials with KBBF-type structures and good properties, for instance, Cs 3 Zn 6 B 9 O 21 , [15] [16] and the A 3 B 3 Li 2 M 4 B 6 O 20 F( A = K, Rb;B = Ba, Sr;M = Al, Ga) [17] series,e tc. Moreover,w efound that simultaneously introducing highly-coordinated cations (such as K, Rb, Cs, Sr and Ba, etc.)…”

“…and BO 3 triangles. The double-layered structures exist in BaAl 2 B 2 O 7 , [20a] A 3 B 3 Li 2 M 4 B 6 O 20 F( A = K, Rb;B = Ba, Sr;M = Al, Ga), [17] Cs 2 Al 2 (B 3 O 6 ) 2 O, [19] CdZn 2 KB 2 O 6 F, [23] etc. Their double layers are composed of single layers that are linked by O/F atoms.…”

BaLiZn3B3O9: a Mixed‐Cation KBe2BO3F2‐Type Zinc‐Borate with a (LiZn3B3O9)∞ Network

“…Yet, the growth of bulk size KBBF crystal is still a major problem for the application of KBBF due to its typical 2D structures and weak interlayer connection (K–F ionic bonding). In order to overcome this problem, numerous KBBF‐related structures such as: Na 2 Be 4 B 4 O 11 , KBe 2 B 3 O 7 , Na 2 CsBe 6 B 5 O 15 (NCBBO), BaBe 2 BO 3 F 3 , SrBe 2 B 2 O 6 and others have been published. However, fewer of them have been grown into big crystals with sufficient size by experiment.…”