Ba1.09Pb0.91Be2(BO3)2F2: The First Pb-Containing Beryllium Borate Fluoride with Trigonal Prismatic PbO6 and 2D [Be3B3O6F3]∞ Layers

Ba_1.09Pb_0.91Be₂(BO₃)₂F₂ (BPBBF), a previously unreported lead-containing beryllium borate fluoride, has been successfully grown through a high-temperature flux method. Its structure is solved by single-crystal X-ray diffraction (SC-XRD), and it is optically characterized via infrared, Raman, UV-vis-IR transmission, and polarizing spectra as well. SC-XRD data suggests that it can be indexed by a trigonal unit cell (space group P3m1) with lattice parameters a = 4.7478(6) Å, c = 8.3856(12) Å, Z = 1, and V = 163.70(5) Å. This material could be considered as a derivative of the Sr₂Be₂B₂O₇ (SBBO) structural motif. It consists of 2D [Be₃B₃O₆F₃]_∞ layers in the crystallographic ab plane, with divalent Ba²⁺ or Pb²⁺ cations serving as spacers among the adjacent layers. Ba and Pb were found to adopt a disordered arrangement in the trigonal prismatic coordination within the BPBBF structural lattice, which is evidenced by both structural refinements against SC-XRD data and energy dispersive spectroscopy. The UV absorption edge (279.1 nm) and birefringence (Δn = 0.054@ 546.1 nm) of BPBBF are confirmed by UV-vis-IR transmission and polarizing spectra, respectively. The discovery of this previous unreported SBBO-type material, BPBBF, along with other reported analogues such as BaMBe₂(BO₃)₂F₂ (M = Ca, Mg, and Cd), provide a prodigious example for tuning the bandgap, birefringence, and short UV absorption edge via simple chemical substitution.

Li3B8O13X (X = Cl and Br): Two New Noncentrosymmetric Crystals with Large Birefringence Induced by BO3 Units

Enthusiasm for the exploration of nonlinear alkali metal borates remains high. Focusing on the Li-B-O-X (X = Cl and Br) system, two examples of noncentrosymmetric borates, Li₃B₈O₁₃Cl and Li₃B₈O₁₃Br, were obtained using a high-temperature solution method under vacuum conditions. Structurally, the Li₃B₈O₁₃X crystals exhibit two independent alternately arranged three-dimensional B-O network structures formed by the basic building block unit B₈O₁₆. The performance measurements demonstrate their short ultraviolet cutoff edges. The theoretical calculation indicates that the BO₃ units dominate the contribution to their large optical anisotropy with the birefringence, 0.094 and 0.088@1064 nm for Li₃B₈O₁₃Cl and Li₃B₈O₁₃Br, respectively.

Crystal structure of the solid solution Ba8.35Pb0.65(B3O6)6

The fundamental building units of Ba_8.35Pb_0.65(B₃O₆)₆ are isolated planar B₃O₆ anionic groups, which are distributed layer upon layer perpendicular to [001], with (Pb/Ba) and Ba sites alternately located between the B₃O₆ sheets.

Single crystals of lead barium borate, Ba_8.35Pb_0.65(B₃O₆)₆, octabarium lead(II) hexa­kis­(triborate), have been obtained by spontaneous nucleation from a high-temperature melt. Its three-dimensional structure is constructed on the basis of a BaO₉ polyhedron, a (Pb/Ba)O₆ octa­hedron (occupancy ratio Pb:Ba = 0.216:0.784) and a condensed B₃O₆ ring anion. In the crystal, the planar B₃O₆ anions are stacked in an alternating fashion with Ba and (Pb/Ba) atoms along [001]. A comparison is made with the structures of related solid solutions in the system Ba/Pb/B/O.

Three new phosphates with isolated P2O7units: noncentrosymmetric Cs2Ba3(P2O7)2and centrosymmetric Cs2BaP2O7and LiCsBaP2O7

Three new phosphates, a noncentrosymmetric (NCS) Cs₂Ba₃(P₂O₇)₂and centrosymmetric (CS) Cs₂BaP₂O₇and LiCsBaP₂O₇, have been synthesized from high-temperature solutions for the first time.