Photoconversion Mechanisms and the Origin of Second-Harmonic Generation in Metal Iodates with Wide Transparency, NaLn(IO₃)₄ (Ln = La, Ce, Sm, and Eu) and NaLa(IO₃)₄:Ln³⁺ (Ln = Sm and Eu)

Abstract

Four new metal iodates, namely, NaLn(IO) (Ln = La, Ce, Sm, and Eu), and a series of NaLa(IO):Ln (Ln = Sm and Eu) solid solutions were synthesized through hydrothermal reactions. The structures of the title compounds are similar to that of NaY(IO) crystallizing in the acentric monoclinic space group Cc. The iodate materials reveal layered structures composed of LnO square antiprisms and IO polyhedra, in which each layer is connected by the I···O interactions. NaLa(IO) suggests a great potential as a matrix for optical source attributed to its acentricity and broad transparency from visible to mid-IR region. The photoluminescence properties depending on the concentration of Sm reveal that NaLa(IO):Sm undergoes a self-quenching relaxation over 7 mol % of Sm by dipole-quadrupole interactions. Attributable to the asymmetric coordination environment of Ln, stronger electric dipole transitions compared to magnetic dipole transitions were observed for both compounds. In addition, the materials exhibit strong second-harmonic generation (SHG) responses and are type I phase-matchable. The structural origin of the SHG properties for the reported iodates is elucidated.

Ce(IO3)2F2⋅H2O: The First Rare‐Earth‐Metal Iodate Fluoride with Large Second Harmonic Generation Response

“…The Ce−O, and Ce−F bond lengths range from 2.342(7) to 2.483(14) Å and from 2.284(4) to 2.287(5) Å, respectively. The I−O bond lengths, which range from 1.775(11) to 1.826(7) Å, are comparable to those of other compounds (Table S2 in the Supporting Information) . Bond valence sum (BVS) calculations on Ce 4+ , I 5+ , O 2− , and F − gave values of 3.81, 5.11–5.06, 1.8–2.05, and 1.18, respectively (Table S1 in the Supporting Information), which are close to their ideal oxidation states and further prove that the coordinations are reasonable.…”

Five New Silver Rare‐Earth Iodates, AgLn(IO3)4 (Ln=Pr, Sm, Dy, Er and Tm): Synthesis, Structures and Properties

“…The results show that the four compounds AgLn(IO 3 ) 4 (Ln= Pr, Sm, Dy and Tm) have SHG efficiencies about 3.2, 2.6, 2.3 and 4 times stronger than KDP, which match well with the above structure description (Figure ). Although the substitution of the rare earth cations does not change the crystal structure, it can be noticed that their frequency doubling effects are not exactly the same, and the difference may come from the different absorption properties of the lanthanide cations . The AgTm(IO 3 ) 4 exhibit large SHG effects (4×KDP), which are very close to AgYb(IO 3 ) 4 (5×KDP) due to the proximity of those elements in the periodic table .…”

REI5O14 (RE=Y and Gd): Promising SHG Materials Featuring the Semicircle‐Shaped I5O143− Polyiodate Anion

“…To the best of our knowledge, the study of metal polyiodates only involves the alkali metal or Ag + and Ba 2+ iodate systems. Many rare‐earth iodates also possess excellent SHG properties, for example, La(IO 3 ) 3 has a large SHG signal of roughly 400× SiO 2 . Accordingly, the combination of a trivalent metal cation such as RE 3+ and a polyiodate anion is expected to afford new SHG materials.…”

“…[35] During the preparation of HBa(IO 3 )(I 4 O 11 ), phosphoric acid played an important role,p robably owing to the fact that the consistencyo ft he reaction media was strengthened by H 3 PO 4 . [35] To the best of our knowledge,t he study of metal polyiodates only involves the alkali metal or Ag + and Ba 2+ iodate systems.Many rare-earth iodates also possess excellent SHG properties, [30,[36][37][38][39][40][41][42] for example,L a(IO 3 ) 3 has al arge SHG signal of roughly 400 SiO 2 . [30] Accordingly,t he combination of at rivalent metal cation such as RE 3+ and apolyiodate anion is expected to afford new SHG materials.…”