BiO(IO₃): A New Polar Iodate that Exhibits an Aurivillius-Type (Bi₂O₂)²⁺ Layer and a Large SHG Response

A new noncentrosymmetric (NCS) and polar material containing two lone-pair cations, Bi³⁺ and I⁵⁺, and exhibiting an Aurivillius-type (Bi₂O₂)²⁺ layer has been synthesized and structurally characterized. The material, BiO(IO₃), exhibits strong second-harmonic generation (SHG), ∼12.5 × KDP (or ∼500 × α-SiO₂), using 1064 nm radiation, and is found in the NCS polar orthorhombic space group Pca2₁ (No. 29). The structure consists of (Bi₂O₂)²⁺ cationic layers that are connected to (IO₃)⁻ anions. The macroscopic polarity, observed along the c-axis direction, may be attributed to the alignment of the IO₃ polyhedra. In addition to the crystal structure and SHG measurements, polarization and piezoelectric measurements were performed, as well as electronic structure analysis.