Bi2Te2O6(NO3)2(OH)2(H2O): A layered bismuth tellurium nitrate hydroxide with multiple noncentrosymmetric chromophores

Abstract

Crystals of a novel bismuth tellurium nitrate hydroxide, Bi2Te2O6(NO3)2(OH)2(H2O), with noncentrosymmetric (NCS) structure have been grown in high yield through a hydrothermal reaction using TeO2, Bi(NO3)3·5H2O, and HNO3 as reagents. Bi2Te2O6(NO3)2(OH)2(H2O) exhibits a layered structure consisting of polyhedra with second-order Jahn-Teller (SOJT) distortive cations, i.e., BiO5, BiO7, Te4+O3, and Te6+O6, as well as anionic π-delocalized NO3− groups. Infrared spectral data not only show all of the vibrations for the constituting bonds, but confirm the existence of -OH groups in the framework of the title compound. UV–vis diffuse reflectance spectrum indicates that Bi2Te2O6(NO3)2(OH)2(H2O) reveals a band gap of ca. 4.0 eV. Thermogravimetric analysis along with powder X-ray diffraction measurements at different temperatures suggest that the crystallinity of Bi2Te2O6(NO3)2(OH)2(H2O) is maintained up to ca. 400 °C. Powder second-harmonic generation (SHG) measurements using 1064 nm radiation reveal that Bi2Te2O6(NO3)2(OH)2(H2O) has SHG efficiency of ca. 20 times that of α-SiO2 and is phase-matchable (Type-I). Local dipole moment calculations for the polyhedra of SOJT distortive cations in Bi2Te2O6(NO3)2(OH)2(H2O) are also presented.