Explorations of New Second-Order Nonlinear Optical Materials in the Ternary Rubidium Iodate System: Noncentrosymmetric β‑RbIO3(HIO3)2 and Centrosymmetric Rb3(IO3)3(I2O5)(HIO3)4(H2O)

Two new rubidium iodates, namely, β-RbIO3(HIO3)2 (1, P1) and Rb3(IO3)3(I2O5)­(HIO3)4(H2O) (2, P21/c), have been synthesized by hydrothermal reaction and their structures determined by single-crystal X-ray diffraction. Compound 1 exhibits IO3– anions and neutral HIO3 molecules which are interconnected by Rb+ cations into three-dimensional structure. Compound 2 features a two-dimensional layered structure formed by IO3– anions and neutral HIO3 and dimeric I2O5 molecules interconnected by Rb+ cations. Large bulk crystal of 1 with dimensions of several millimeters has been grown. UV–vis–NIR transmission spectroscopy measurements on a slab of a polished crystal of 1 indicated that the crystal possesses a short-wavelength absorption edge onset at 305 nm. Powder second-harmonic generation (SHG) measurements on sieved crystals revealed that 1 is a type I phase-matchable material with an SHG response about 1.5 times that of KH2PO4. The Vickers hardness of crystal of 1 has been measured to be 110 HV, and the laser-induced damage threshold has been confirmed to be 18.26 J/cm2 with a laser wavelength of 1064 nm and a pulse duration of 10 ns. Moreover, thermal stabilities and vibrational spectra for both 1 and 2 have also been studied.本研究通过水热反应合成了两种新型碘酸铷化合物，分别为β-RbIO3(HIO3)2（化合物1，空间群P1）与Rb3(IO3)3(I2O5)(HIO3)4(H2O)（化合物2，空间群P21/c），并借助单晶X射线衍射解析了其晶体结构。化合物1的结构中存在IO3⁻阴离子与中性HIO3分子，二者通过Rb⁺阳离子相互连接，形成三维网状骨架。化合物2则呈现二维层状结构，由IO3⁻阴离子、中性HIO3分子与二聚态I2O5分子通过Rb⁺阳离子交联构成。已成功生长出尺寸达数毫米的块状化合物1单晶。对抛光后的化合物1晶体切片进行紫外-可见-近红外透射光谱测试，结果表明其短波吸收边起始波长为305 nm。粉末倍频效应（SHG）测试显示，化合物1属于I类相位匹配材料，其倍频响应强度约为磷酸二氢钾（KH2PO4）的1.5倍。经测试，化合物1晶体的维氏硬度为110 HV，在激光波长1064 nm、脉冲宽度10 ns的测试条件下，其激光损伤阈值为18.26 J/cm²。此外，本研究还对两种化合物的热稳定性与振动光谱进行了表征分析。