Growth, Structure, and Optical Properties of a Nonlinear Optical Niobium Borate Crystal CsNbOB₂O₅ with Distorted NbO₅ Square Pyramids

Abstract

In this paper, a revised structure determination of an already known compound CsNbOB2O5 with new structural insights was performed and the detailed characterization of its optical properties was reported for the first time. CsNbOB2O5 was synthesized by spontaneous crystallization. It crystallizes in the Pmn21 space group, and the unit lattice parameters are a = 7.5220(7) Å, b = 3.9881(4) Å, c = 9.7167(9) Å, and Z = 2. In the structure of CsNbOB2O5, a [NbO5] square pyramid and [B2O5] unit are linked to constitute an infinitely extended two-dimensional ∞ 2[NbOB2O5] layer via sharing oxygen atoms. Between these two-dimensional layers, there are no covalent bonds perpendicular to their planes based on Mulliken bond order analysis. CsNbOB2O5 has a wide band gap (4.52 eV) and a large second-harmonic-generation (SHG) response (1.2 × KDP) and demonstrates type-I phase-matchable behavior. First-principles simulations reveal that the birefringence is approximately 0.10. Moreover, SHG-weighted charge density analysis shows that the primary source of the nonlinearity of the title compound is the distorted NbO5 square pyramids.

Mixed Alkali Metal and Alkaline Earth Metal Scandium Borate Birefringence Material with Layered Structure and Short Ultraviolet Cutoff Edge

“…Because alkali metals and alkaline earth metals are free of d–d and f–f electron transitions, they can make the material a large transparent window, especially in the UV area. − Naturally, when investigating novel UV/DUV scandium borate birefringence materials, we use alkali metals and alkaline earth metals as the material charge balancing cations. Exploring the alkali metal alkaline earth metal scandium borate system yielded the discovery of a scandium borate material, RbBaScB 6 O 12 .…”

Improvement on Magnetocaloric Effect through Structural Evolution in Gadolinium Borate Halides Ba2Gd(BO3)2X (X = F, Cl)

“…At 250 nm, the reflectance reaches 70.45%, the cutoff edge of Ba 2 Gd­(BO 3 ) 2 F is lower than 250 nm. The experimental band gap value was estimated to be 5.88 eV according to the Tauc technique. , The good reflectance and the big band gap imply that Ba 2 Gd­(BO 3 ) 2 F has a possible application in the UV band. , …”

“…63,64 The good reflectance and the big band gap imply that Ba 2 Gd(BO 3 ) 2 F has a possible application in the UV band. 65,66 Electronic Structure Calculations. The calculated band structure of Ba 2 Gd(BO 3 ) 2 F is displayed in Figure S5a.…”

Synthesis and characterization of a new rare earth borate nonlinear optical crystal K7PbLu2B15O30

“…The most prevalent ones are B 2 O 5 , B 3 O 6 , B 3 O 7 , B 4 O 9 , B 5 O 10 , and B 8 O 15 units. [23][24][25][26][27][28][29][30] The rich structure type of borates is very favorable to produce compounds with non-centrosymmetric structures. Moreover, borates can be used in the UV/DUV area due in large part to the significant electronegativity difference between the B and O elements, which is very beneficial for improving the transmission of crystals at short wavelengths and increasing the laser damage threshold.…”