Pb<sub>18</sub>O<sub>8</sub>Cl<sub>15</sub>I<sub>5</sub>: A Polar Lead Mixed Oxyhalide with Unprecedented Architecture and Excellent Infrared Nonlinear Optical Properties
Xinglong Chen, Qun Jing, Kang Min Ok
Abstract
Abstract To develop high‐performance nonlinear optical (NLO) materials for infrared (IR) applications, we have applied a rational element‐composition design strategy and investigated the unexplored PbO–PbCl 2 –PbI 2 system. By doing so, we discovered a new polar lead mixed oxyhalide, Pb 18 O 8 Cl 15 I 5 , the first synthetic metal oxyhalide combining both Cl − and I − . Pb 18 O 8 Cl 15 I 5 reveals an unprecedented structural feature with two different dimensional types of oxocentered Pb–O units, namely, [O 4 Pb 8 ] 8+ clusters and [OPb 2 ] 2+ chains. Centimeter‐sized single crystals of Pb 18 O 8 Cl 15 I 5 have been successfully grown under ambient conditions. Remarkably, Pb 18 O 8 Cl 15 I 5 satisfies all fundamental yet rigorous criteria for high‐performance IR NLO materials, exhibiting the widest IR transparency (up to 16.0 μm) among oxide‐based crystals, strong second‐harmonic generation response (1.05×AgGaS 2 ), superior birefringence (0.086 at 636 nm), and a high laser‐induced damage threshold (8.5×AgGaS 2 ).