Abstract
Transparent single crystals of two new iodates K3Sc(IO3)6 and KSc(IO3)3Cl have been synthesized hydrothermally. Single-crystal X-ray diffraction was used to determine their crystal structures. Both compounds crystallize in non-centrosymmetric space groups. The compound K3Sc(IO3)6 crystallizes in the orthorhombic space group Fdd2. The crystal structure is made up of [ScO6] octahedra, [IO3] trigonal pyramids, and [KO8] distorted cubes. The compound KSc(IO3)3Cl crystallizes in the trigonal space group R3. The building blocks are [ScO6] octahedra, [KO12] polyhedra, and [IO3] trigonal pyramids. The Cl– ions act as counter ions and reside in tunnels in the crystal structure. The second harmonic generation (SHG) measurements at room temperature, using 1064 nm radiation, on polycrystalline samples show that the SHG intensities of K3Sc(IO3)6 and KSc(IO3)3Cl are around 2.8 and 2.5 times that of KH2PO4 (KDP), respectively. In addition, K3Sc(IO3)6 and KSc(IO3)3Cl are phase-matchable at the fundamental wavelength of 1064 nm. The large anharmonicity in the optical response of both compounds is further supported by an anomalous temperature dependence of optical phonon frequencies as well as their enlarged intensities in Raman scattering. The latter corresponds to a very large electronic polarizability.
Highlights
New strategies for designing non-centrosymmetric (NCS) materials are attracting interest because of their potential technological applications
A synthetic strategy that has proven successful to increase the probability to form NCS compounds is to include acentric building units in the crystal structure.[4−6] Lone electron pair cations of p-elements such as I5+, Te4+, or Se4+ comprise an active electron pair that occupies space and has a volume that can be compared with the volume of an O2− anion
System, with L = Bi3+, and show optical activity, e.g. BiO(IO3)[9] and Bi2(IO4)(IO3)3.10 the system A−L−I5+−O exists with relevant reported compounds belonging to A2BiI5O15, where A = K+ or Rb+ and L = Bi3+
Summary
New strategies for designing non-centrosymmetric (NCS) materials are attracting interest because of their potential technological applications. The K+−Sc3+−I5+−O and K+−Sc3+−I5+−Cl systems are explored, and two new NCS compounds are reported, K3Sc(IO3)[6] and KSc(IO3)3Cl. Both are SHG active with intensities that are approximately 2.8 and 2.5 times that of KDP for K3Sc(IO3)[6] and KSc(IO3)3Cl, respectively. There are three building units in the crystal structure, [KO8] distorted cubes, [ScO6] octahedra, and [IO3] trigonal pyramids.
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