Pb2B10O16(OH)2·B(OH)3·H2O: significantly enhanced second harmonic generation via substituting metal cations in isostructural compounds with Pb2+

Abstract

Substitution is an effective way to design and synthesize borates with unique structures and excellent performances. A new hydrated borate, Pb₂B₁₀O₁₆(OH)₂·B(OH)₃·H₂O, was obtained via substituting M²⁺ cations in M₂B₁₀O₁₆(OH)₂·B(OH)₃·H₂O (M = Sr, Ca, or Ba) with Pb²⁺. It crystallizes into chiral space group P2₁ and features a layered B–O anionic framework similar to M₂B₁₀O₁₆(OH)₂·B(OH)₃·H₂O (M = Sr, Ca, or Ba). The fundamental building units (FBUs) are [B₅O₁₀(OH)] groups, which further constitute ²[B₅O₈(OH)]_∞ layers through sharing vertex oxygen atoms. It possesses a broad transmittance range and the ultraviolet cutoff edge is about 204 nm. Owing to the effect of the stereochemically active lone pair of Pb²⁺, it features a second harmonic generation (SHG) response of approximatively 2.1 times that of KH₂PO₄ (KDP).