Functional Materials Design via Structural Regulation Originated from Ions Introduction: A Study Case in Cesium Iodate System

Tailored
structural regulation to achieve novel compounds with
special properties is very attractive and important for functional
material design. In this paper, CsIO3 was selected as a
maternal structure and three new derivatives, namely, CsIO2F2, Cs3(IO2F2)3·H2O, and Cs­(IO2F2)2·H5O2, were successfully prepared by introducing
different units (F–, H2O, H5O2+, and IO2F2–) under hydrothermal condition for the first time. Then, the structural
transformations were schematically analyzed and the corresponding
properties originated from ions introduction were investigated. Therein,
noncentrosymmetric CsIO3 and CsIO2F2 exhibit good nonlinear optical properties with large second-harmonic
generation (SHG) effects (15 × and 3 × KH2PO4), wide band gaps (4.2 and 4.5 eV), wide transmittance ranges
(∼0.27–5.5 μm), and high laser damage thresholds
(15 × and 20 × AgGaS2, respectively), which shows
that they are potential nonlinear optical materials in near-ultraviolet
to mid-infrared. To further analyze the structure–properties
relationship, the first-principles calculations are applied to explore
the origins of the optical properties, such as birefringences and
SHG responses. Moreover, the protonated (H5O2)+ cations in Cs­(IO2F2)2·H5O2 imply that it may feature enhanced
conductivity, which was tentatively verified by the resistivity tests
via the conventional dc four-probe method. The study
case of structural regulation realized by ions introduction in this
work may give a feasible guidance for functional materials design.