CaCe(IO3)3(IO3F)F: a promising nonlinear optical material containing both IO3− and IO3F2− anions

Abstract

The first noncentrosymmetric (NCS) rare earth fluoroiodate, CaCe(IO₃)₃(IO₃F)F, has been hydrothermally synthesized through rational chemical substitution. Substituting one IO₃⁻ group with one IO₃F²⁻ unit and two Li⁺ cations with a Ca²⁺ cation in Li₂Ce(IO₃)₄F₂ transforms the symmetry from centrosymmetric (CS) to NCS. CaCe(IO₃)₃(IO₃F)F crystallizes in the polar space group Pna2₁ and features a novel two-dimensional [Ce(IO₃F)]²⁺ layer composed of Ce⁴⁺ cations bridged by IO₃F²⁻ units. Interestingly, the title compound exhibits a strong second-harmonic-generation (SHG) response of 5 times that of KDP, a wide optical transparent window (0.5–11 μm), a suitable birefringence of 0.071@1064 nm and a high laser-induced damage threshold (LIDT) (approximately 18.5 × AgGaS₂), indicating that CaCe(IO₃)₃(IO₃F)F is a potential material for visible to mid-infrared SHG applications. This work implies that the combination of IO₃F²⁻ and IO₃⁻ groups may be an efficient route to develop SHG materials based on metal iodates.