Article Cite This: Inorg. Chem. XXXX, XXX, XXX-XXX
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Li7(TeO3)3F: A Lithium Fluoride Tellurite with Large Second Harmonic Generation Responses and a Short Ultraviolet Cutoff Edge Jiang-He Feng,†,§ Chun-Li Hu,† Hou-Ping Xia,‡ Fang Kong,† and Jiang-Gao Mao*,† †
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, P. R. China ‡ College of Physics and Optoelectronics Technology, Baoji University of Arts and Sciences, Baoji, Shanxi 721016, P. R. China § Graduate School of the Chinese Academy of Sciences, Beijing, 100039, P. R. China S Supporting Information *
ABSTRACT: Here, the combination of the strong electropositive lithium and the most electronegative fluorine with the TeO3 group afforded the first lithium fluoride tellurite, namely, Li7(TeO3)3F (P63), which was synthesized by solid-state reactions. Its structure features a novel three-dimensional anionic framework of [Li7O9F]12− composed of LiO3F and LiO4 tetrahedra with one-dimensional hexagonal tunnels of 12-membered rings along the c-axis, filled by the “isolated” ψ-TeO3 tetrahedra. Notably, this compound displays the largest band gap of 4.75 eV among all of the noncentrosymmetric metal-tellurites reported so far, as well as strong second harmonic generation (SHG) responses (3 × KH2PO4 @1064 nm, 0.2 × β-BaB2O4 @532 nm) and a large laser damage threshold (73 × AgGaS2). Furthermore, theoretical calculations reveal that the LiO4 and LiO3F tetrahedra also contribute significantly to the SHG response (∼30%).
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KDP, 3.34 eV),25 and Cs(TiOF)3(SeO3)2 (5× KDP, 3.50 eV).26 Compared with the metal selenites, tellurites can exhibit much richer structural chemistries, because Te(IV) can adopt a variety of coordination inodes of TeO3, TeO4, and TeO5, and these Te(IV)−O groups can be further condensed into zerodimensional (0D) clusters (Te3O84−, Te4O116−, Te5O136−), one-dimensional (1D) chains (Te4O104−, Te6O132−), and twodimensional (2D) layers (Te4O92−, Te4O52−).6 Hence we believe that a variety of new NCS tellurite fluorides with good SHG properties can be prepared. Fluoride can form M−F and Te−F bonds in metal tellurites,27−30 but the formation of Te−F bond is undesirable for SHG, since it will reduce greatly the dipole moment of the tellurite groups as for metal iodates; for example, RbIO2F2 (4 × KDP) with a (IO2F2)− unit displays much weaker SHG response compared with RbIO3 (10 × KDP).31 The bismuth iodate fluoride BiF2(IO3) reported by our group exhibits very large SHG responses (11.5 × KDP @ 1064 nm and 1.0 × KTiOPO4 (KTP) @ 2.05 μm).32 Therefore, it is more meaningful to isolate metal tellurite fluoride rather than fluoro-tellurite with M−F bonds. However, almost all of metal fluoride tellurites reported are structurally centrosymmetric, including V2Te2O7F2,30 TiTeO3F2,30 Cu7(TeO3)3F2,33 InTeO3F7,34 KTe3O6F,35 and KTeO2F.36 Hence, it prompted us to search high-performance SHG fluoride tellurites in other systems. It is known that lithium is inclined to form asymmetrically covalent LiOxF4−x (x = 0−4) tetrahedra,
INTRODUCTION Inorganic nonlinear optical (NLO) materials play a crucial role in expanding the spectral range of solid-state laser through frequency conversion technology, owing to their excellent NLO properties, such as large nonlinear coefficients, wide transparent windows, good thermal and chemical stabilities, and so forth.1−11 Among them, metal selenites and tellurites are more likely to form non-centrosymmetric (NCS) structure as the prerequisite of second-harmonic generation (SHG) property, due to the stereochemically active lone pairs on Se4+ or Te4+ cation susceptible to second-order Jahn−Teller (SOJT). During the past two decades, through the combination of distorted octahedrally coordinated d0 transition metal with Se4+ and Te4+ cations, a large number of compounds with excellent SHG properties have been discovered, such as βBaTeMo2O9 (600 × α-SiO2),12 Na2TeW2O9 (500 × αSiO2),13,14 Cs2TeW3O12 (400 × α-SiO2),15−17 and A2(MoO3)3(SeO3) (A = Tl, NH4) (400 × α-SiO2).18 Nonetheless, the majorities of them are of small band gaps (Eg) and complex chemical compositions, which hinder their applications in UV− visible region; also, their bulk single-crystal growths are difficult. The introduction of fluoride into NCS materials has been found to be an effective way to blue shift the UV cutoff edge and enhance the SHG efficiency, especially in deep-UV region, as exampled by KBe2BO3F2 (
