Pb₂BO₃I: A Borate Iodide with the Largest Second‐Harmonic Generation (SHG) Response in the KBe₂BO₃F₂ (KBBF) Family of Nonlinear Optical (NLO) Materials

Abstract

Borate halides are an ideal materials class from which to design high-performance nonlinear optical (NLO) materials. Currently, borate fluorides, chlorides, and bromides are extensively investigated while borate iodide materials discovery remains rare because of the perceived synthetic challenges. We report a new borate iodide, Pb₂ BO₃ I, synthesized by a straightforward hydrothermal method. The Pb₂ BO₃ I chemical formula conceals that the compound exhibits a structure similar to the well-established KBe₂ BO₃ F₂ (KBBF), which we show supports the highest second-harmonic generation (SHG) at 1064 nm in the KBBF family, 10 × KH₂ PO₄ (KDP), arising from the inclusion of Pb²⁺ and I^- and the crystal chemistry. Our work shows that KBBF-related compounds can be synthesized incorporating iodide and exhibit superior NLO responses.