BiO(IO_3): A New Polar lodate that Exhibits an Aurivillius-Type (Bi_2O_2)~(2+) Layer and a Large SHG Response

摘要

A new noncentrosymmetric (NCS) and polar material containing two lone-pair cations, Bi~(3+) and I~(5+), and exhibiting an Aurivillius-type (Bi_2O_2)~(2+) layer has been synthesized and structurally characterized. The material, BiO(IO_3), exhibits strong second-harmonic generation (SHG), ～12.5×KDP (or ～500 ×α-SiO_2), using 1064 nm radiation, and is found in the NCS polar orthor-hombic space group Pca2_1 (No. 29). The structure consists of (Bi_2O_2)~(2+) cationic layers that are connected to (IO_3)-anions. The macroscopic polarity, observed along the c-axis direction, may be attributed to the alignment of the IO_3 polyhedra. In addition to the crystal structure and SHG measurements, polarization and piezoelectric measurements were performed, as well as electronic structure analysis.