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Kang Min Ok

Publications and source records attributed to Kang Min Ok.

15 recordsLinked to original sources
PubMed2006

New layered uranium phosphate fluorides: syntheses, structures, characterizations, and ion-exchange properties of A(UO2)F(HPO4).xH2O (A = Cs+, Rb+, K+; x = 0-1).

Single crystals of three new layered uranium phosphate fluorides, A(UO2)F(HPO4).xH2O (A = Cs+, Rb+, and K+; x = 0-1) have been synthesized by hydrothermal reactions using UO3, H3PO4, HF, and corresponding alkali metal halides as reagents. Although all three new materials have layered structures, each of them contains different structural motifs within the layer. While Cs(UO2)F(HPO4).0.5H2O and Rb(UO2)F(HPO4) reveal noncentrosymmetric crystal structures, K(UO2)F(HPO4).H2O crystallizes in a centrosymmetric space group. In addition, the ion-exchanged phases for all three materials are highly crystalline. Crystal data: Cs(UO2)F(HPO4).0.5H2O, orthorhombic, space group Pca21 (No. 29), with a = 25.656(5) A, b = 6.0394(12) A, c = 9.2072(18) A, and Z = 4; Rb(UO2)F(HPO4), orthorhombic, space group Cmc21 (No. 36), with a = 17.719(4) A, b = 6.8771(14) A, c = 12.139(2) A, and Z = 8; K(UO2)F(HPO4).H2O, monoclinic, P21/n (No. 14), with a = 6.7885(14) A, b = 8.7024(17) A, c = 12.020(2) A, beta = 94.09(3), and Z = 4.

Journal Article↗
PubMed2006

Directed synthesis of noncentrosymmetric molybdates using composition space analysis.

A systematic investigation of the factors governing the reaction product composition, hydrogen bonding, and symmetry was conducted in the MoO3/3-aminoquinuclidine/H2O system. Composition space analysis was performed through 36 individual reactions under mild hydrothermal conditions using racemic 3-aminoquinuclidine. Single crystals of three new compounds, [C7H16N2][Mo3O10] x H2O, [C7H16N2]2[Mo8O26] x H2O, and [C7H16N2]2[Mo8O26] x 4 H2O, were grown. The relative phase stabilities for these products are dependent upon the reactant mole fractions in the initial reaction gel. This phase stability information was used to direct the synthesis of two new noncentrosymmetric compounds, using either (S)-(-)-3-aminoquinuclidine dihydrochloride or (R)-(+)-3-aminoquinuclidine dihydrochloride. [(R)-C7H16N2]2[Mo8O26] and [(S)-C7H16N2]2[Mo8O26] both crystallize in the noncentrosymmetric space group P2(1) (No. 4), which has the polar crystal class 2 (C2). The second-harmonic generation activities were measured on sieved powders. The structure-directing properties of the molybdate components in each compound were determined using bond valence sums. The structures of all five compounds were determined using single-crystal X-ray diffraction.

Journal Article↗
PubMed2006

Synthesis, structure, and characterization of novel two- and three-dimensional vanadates: Ba2.5(VO2)3(SeO3)4.H2O and La(VO2)3(TeO6).3H2O.

Two new vanadates, Ba(2.5)(VO2)3(SeO3)4.H2O and La(VO2)3(TeO6).3H2O, have been synthesized by hydrothermal methods using BaCO3, Ba(OH)2.H2O, La(NO3)3.6H2O, V2O5, TeO2, and H2SeO3 as reagents. The structures were determined by single-crystal X-ray diffraction. Ba(2.5)(VO2)3(SeO3)4.H2O exhibits a two-dimensional layered structure consisting of VO(5) square pyramids and SeO3 polyhedra, whereas La(VO2)3(TeO6).3H2O has a three-dimensional framework structure composed of VO(4) tetrahedra and TeO6 octahedra. Infrared and Raman spectroscopy, UV-vis diffuse reflectance spectroscopy, and thermogravimetric analysis are also presented. Crystal data: Ba(2.5)(VO2)3(SeO3)4.H2O, trigonal, space group P (No. 147) with a = b = 12.8279(15) A, c = 7.2631(9) A, V = 1035.1(2) A(3), and Z = 2; La(VO2)3(TeO6).3H2O, trigonal, space group R3c (No. 161) with a = b = 9.4577(16) A, c = 23.455(7) A, V = 1816.9(7) A3, and Z = 6.

Journal Article↗
PubMed2006

Bulk characterization methods for non-centrosymmetric materials: second-harmonic generation, piezoelectricity, pyroelectricity, and ferroelectricity.

Characterization methods for bulk non-centrosymmetric compounds are described. These methods include second-harmonic generation, piezoelectricity, pyroelectricity, and ferroelectricity. In this tutorial review with each phenomenon, details are given of the measurement techniques along with a brief history and background. Finally, data interpretation is discussed.

Journal Article↗
PubMed2005

New metal iodates: syntheses, structures, and characterizations of noncentrosymmetric La(IO3)3 and NaYI4O12 and Centrosymmetric beta-Cs2I4O11 and Rb2I6O15(OH)2.H2O.

Four new metal iodates, beta-Cs2I4O11, Rb2I6O15(OH)2.H2O, La(IO3)3, and NaYI4O12, have been synthesized hydrothermally, and the structures were determined by single-crystal X-ray diffraction techniques. All of the reported materials contain I5+ cations that are in asymmetric coordination environments attributable to their stereoactive lone pair. Second-order nonlinear optical measurements on noncentrosymmetric La(IO3)3 and NaYI4O12, using 1064-nm radiation, indicate that both materials have second-harmonic-generating properties with efficiencies of approximately 400xSiO2. Converse piezoelectric measurements revealed d33 values of 5 and 138 pm V-1 for La(IO3)3 and NaYI4O12, respectively. Infrared and Raman spectroscopy and thermogravimetric analyses are also presented for all of the reported materials. Crystal data: beta-Cs2I4O11, monoclinic, space group P2(1)/n (No. 14), with a=12.7662(14) A, b=7.4598(8) A, c=14.4044(16) A, beta=106.993(2) degrees, V=1311.9(2) A3, and Z=4; Rb2I6O15(OH)2.H2O, triclinic, space group P (No. 2), with a=7.0652(17) A, b=7.5066(18) A, c=18.262(4) A, alpha=79.679(4) degrees, beta=85.185(4) degrees, gamma=70.684(4) degrees, V=898.9(4) A3, and Z=2; La(IO3)3, monoclinic, space group Cc (No. 9), with a=12.526(2) A, b=7.0939(9) A, c=27.823(4) A, beta=101.975(4) degrees, V=2418.4(6) A3, and Z=4; NaYI4O12, monoclinic, space group Cc (No. 9), with a=31.235(3) A, b=5.5679(5) A, c=12.5451(12) A, beta=91.120(3) degrees, V=2181.3(4) A3, and Z=4.

Journal Article↗
PubMed2005

Mixed-metal tellurites: synthesis, structure, and characterization of Na1.4Nb3Te4.9O18 and NaNb3Te4O16.

Two new mixed-metal tellurites, Na1.4Nb3Te4.9O18 and NaNb3Te4O16, have been synthesized by standard solid-state techniques using Na2CO3, Nb2O5, and TeO2 as reagents. The structures of Na1.4Nb3Te4.9O18 and NaNb3Te4O16 were determined by single-crystal X-ray diffraction. Both of the materials exhibit three-dimensional structures composed of NbO6 octahedra, TeO4, and TeO3 polyhedra. The Nb5+ and Te4+ cations are in asymmetric coordination environments attributable to second-order Jahn-Teller (SOJT) effects. The Nb5+ cations undergo an intraoctahedral distortion toward a corner (local C4 direction), whereas the Te4+ cations are in distorted environments owing to their nonbonded electron pair. Infrared and Raman spectroscopy, UV-vis diffuse reflectance spectroscopy, thermogravimetric analysis, and dielectric measurements were also performed on the reported materials. Crystal data: Na1.4Nb3Te4.9O18, monoclinic, space group C2/m (No. 12), with a = 32.377(5) A, b = 7.4541(11) A, c = 6.5649(9) A, beta = 95.636(5) degrees, V = 1576.7(4) A3, and Z = 4; NaNb3Te4O16, monoclinic, space group P2(1)/m (No. 11), with a = 6.6126(13) A, b = 7.4738(15) A, c = 14.034(3) A, beta = 102.98(3) degrees, V = 675.9(3) A3, and Z = 2.

Journal Article↗
PubMed2005

New d0 transition metal iodates: synthesis, structure, and characterization of BaTi(IO3)6, LaTiO(IO3)5, Ba2VO2(IO3)4.(IO3), K2MoO2(IO3)4, and BaMoO2(IO3)4.H2O.

Five new d0 transition metal iodates, BaTi(IO3)6, LaTiO(IO3)5, Ba2VO2(IO3)4.(IO3), K2MoO2(IO3)4, and BaMoO2(IO3)4.H2O, have been synthesized by hydrothermal methods using Ba(OH)2.8H2O, La2O3, K2CO3, TiO2, V2O5, MoO3, and HIO3 as reagents. The structures of these compounds were determined by single-crystal X-ray diffraction. All of the reported materials have zero-dimensional or pseudo-one-dimensional crystal structures composed of MO6 (M = Ti4+, V5+, or Mo6+) octahedra connected to IO3 polyhedra. Infrared and Raman spectroscopy, thermogravimetric analysis, and UV-vis diffuse reflectance spectroscopy are also presented. Crystal data: BaTi(IO3)6, trigonal, space group R-3 (No. 148), with a = b = 11.4711(10) A, c = 11.1465(17) A, V = 1270.2(2) A3, and Z = 3; LaTiO(IO3)5, monoclinic, space group P2(1)/n (No. 14), with a = 7.4798(10) A, b = 18.065(2) A, c = 10.4843(14) A, beta = 91.742(2) degrees , V = 1416.0(3) A3, and Z = 4; Ba2VO2(IO3)4.(IO3), monoclinic, space group P2(1)/c (No. 14), with a = 7.5012(9) A, b = 33.032(4) A, c = 7.2150(9) A, beta = 116.612(2) degrees , V = 1598.3(3) A3, and Z = 4; K2MoO2(IO3)4, monoclinic, space group C2/c (No. 15), with a = 12.959(2) A, b = 6.0793(9) A, c = 17.748(3) A, beta = 102.410(4) degrees , V = 1365.5(4) A3, and Z = 4; BaMoO2(IO3)4.H(2)O, monoclinic, space group P2(1)/n (No. 14), with a = 13.3368(17) A, b = 5.6846(7) A, c = 18.405(2) A, beta = 103.636(2) degrees , V = 1356.0(3) A3, and Z = 4.

Journal Article↗
PubMed2004

Asymmetric cationic coordination environments in new oxide materials: synthesis and characterization of Pb(4)Te(6)M(10)O(41) (M = Nb(5+) or Ta(5+)).

Two new isostructural tellurites, Pb(4)Te(6)M(10)O(41) (M = Nb(5+) or Ta(5+)), have been synthesized by standard solid-state techniques using PbO, Nb(2)O(5) (or Ta(2)O(5)), and TeO(2) as reagents. The structures of Pb(4)Te(6)Nb(10)O(41) and Pb(4)Te(6)Ta(10)O(41) were determined by single-crystal and powder X-ray diffraction. The materials exhibit a three-dimensional framework consisting of layers of corner-shared NbO(6) octahedra connected by TeO(3) and PbO(6) polyhedra. The Nb(5+), Te(4+), and Pb(2+) cations are in asymmetric coordination environments attributable to second-order Jahn-Teller effects. The Nb(5+) cations undergo an intraoctahedral distortion either toward a face or a corner, whereas the Te(4+) and Pb(2+) cations are in distorted environments attributable to their lone pair. In addition, the TeO(3) polyhedra strongly influence the direction of the Nb(5+) intraoctahedral distortion. Infrared and Raman spectroscopy, thermogravimetric analysis, and dielectric measurements are also presented. Crystal data: Pb(4)Te(6)Nb(10)O(41), monoclinic, space group C2/m (No. 12), with a = 23.412(3) A, b = 20.114(3) A, c = 7.5008(10) A, beta = 99.630(4) degrees, V = 3482.4(8) A(3), and Z = 4; Pb(4)Te(6)Ta(10)O(41), monoclinic, space group C2/m (No. 12), with a = 23.340(8) A, b = 20.068(5) A, c = 7.472(2) A, beta = 99.27(3) degrees, V = 3453.8(2) A(3), and Z = 4.

Journal Article↗
PubMed2004

Synthesis, structure, and characterization of two new layered mixed-metal phosphates, BaTeMO4(PO4) (M = Nb5+ or Ta5+.

Two new isostructural mixed-metal phosphates, BaTeMO(4)(PO(4)) (M = Nb(5+) or Ta(5+)), have been synthesized as bulk phase powders and single crystals by standard solid-state techniques using BaCO(3), TeO(2), Nb(2)O(5) (or Ta(2)O(5)), and NH(4)H(2)PO(4) as reagents. The materials have novel layered crystal structures consisting of [M(5+)O(6/2)](-) corner-sharing octahedral chains that are connected to [Te(4+)O(4/2)](0) polyhedra and [P(5+)O(2/1)O(2/2)](-) tetrahedra. The Ba(2+) cations reside between the layers and maintain charge balance. The Te(4+) cations are in asymmetric coordination environments attributable to their lone pairs. The Nb(5+) distorts along the local C(4) direction of its octahedron resulting in a "short-long-short-long" Nb-O-Nb bond motif. The Nb(5+) cation displaces away from the oxide ligands that are bonded to Te(4+) or P(5+) cations, attributable to the structural rigidity of the TeO(4) and PO(4) polyhedra. Thus, the TeO(4) and PO(4) polyhedra support and reinforce the intraoctahedral distortion observed within the NbO(6) octahedra. Infrared and Raman spectroscopy, thermogravimetric analysis, and ion-exchange experiments are also presented. Crystal data: BaTeNbO(4)(PO(4)), orthorhombic, space group Pbca (No. 61), with a = 6.7351(9) A, b = 7.5540(10) A, c = 27.455(4) A, V = 1396.8(3) A(3), and Z = 8; BaTeTaO(4)(PO(4)), orthorhombic, space group Pbca (No. 61), with a = 6.734(2) A, b = 7.565(3) A, c = 27.435(9) A, V = 1372.6(8) A(3), and Z = 8.

Journal Article↗
PubMed2004

Synthesis and characterization of two novel mixed metal tellurates: KGaTeO5 x H2O and K3GaTe2O8(OH)2 x H2O.

Single crystals of KGaTeO5 x H2O and K3GaTe2O8(OH)2 x H2O have been synthesized by supercritical hydrothermal techniques using Te(OH)6, Ga2O3 and KOH as reagents, and characterized by single crystal X-ray diffraction, thermal analysis, IR and Raman spectroscopy. Ion-exchange studies revealed KGaTeO5 x H2O, with its open-framework structure, is capable of exchanging both smaller (Na+) and larger (Rb+) ions. In addition, higher thermal stability and reversible hydration properties were observed for KGaTeO5 x H2O.

Crystallography, X-Ray↗
PubMed2003

Combining second-order Jahn-Teller distorted cations to create highly efficient SHG materials: synthesis, characterization, and NLO properties of BaTeM2O9 (M = Mo6+ or W6+).

Two new oxides, BaTeMo2O9 and BaTeW2O9, have been synthesized, by standard solid-state techniques, that have strong SHG intensities of approximately 600 x SiO2, on the order of LiNbO3. Both materials contain cations susceptible to second-order Jahn-Teller (SOJT) distortions, resulting in asymmetric coordination environments. The SOJT distortion polarizes the M6+-O and Te4+-O bonds. Equally importantly, these polarizations constructively add, resulting in the large SHG responses. Powder SHG measurements on BaTeM2O9 (M = Mo6+ or W6+) indicated that both materials are phase-matchable and have a deffexp of 28 and 22 pm/V, respectively. Using bond hyperpolarizability values (beta's) of 130 x 10-40 and 305 x 10-40 m4/V for Te4+-O and Mo6+-O respectively, we calculate a deffcalc of 20pm/V for BaTeMo2O9. In addition, through the powder SHG measurements, we are able to give a more reasonable value for beta(W6+-O), 230 x 10-40 m4/V. This value is consistent with the smaller polarizability and magnitude of the intra-octahedral distortion of W6+ compared with Mo6+.

Journal Article↗
PubMed2002

From linear inorganic chains to helices: chirality in the M(pyz)(H(2)O)(2)MoO(2)F(4) (M = Zn, Cd) compounds.

Cd(C(4)H(4)N(2))(H(2)O)(2)MoO(2)F(4) (C(4)H(4)N(2) = pyrazine, pyz) was synthesized via hydro(solvato)thermal methods and characterized by single-crystal X-ray diffraction methods (P3(2)()21, no. 154, Z = 3, a = 7.4328(7) A, c = 16.376(2) A). Both of the known M(pyz)(H(2)O)(2)MoO(2)F(4) (M = Zn, Cd) compounds are comprised of trans-M(pyz)(2)(OH(2))(2)F(2) and cis-MoO(2)F(4) octahedra that share fluoride vertices to form helical chains along the 3-fold screw axes. Individual chains are bridged to six symmetry-equivalent helices through metal-pyrazine and OH(2)...F and OH(2)...O hydrogen bonds. Structural comparisons of similar oxyfluoride chains demonstrate that they can be varied from linear to helical through (1) the replacement of pyridine or pyrazine by H(2)O molecules and (2) the substitution of cis-directing MoO(2)F(4)(2-) anions in place of trans-directing WO(2)F(4)(2-) or TiF(6)(2-) anions. Infrared absorption (IR) measurements for M = Cd show two distinct O-H stretches corresponding to hydrogen-bonded O-H...F and O-H...O groups. Contrastingly for M = Zn, IR measurements exhibit O-H stretches for averaged hydrogen-bonded O-H...(O/F) groups, free (unbound) O-H groups, and higher energy Mo-F stretches. The IR data suggest a small fraction of the O-H...F hydrogen bonds are broken in the M = Zn analogue as a result of the racemic twinning. Both compounds exhibit nonlinear optical behavior, with second harmonic generation (SHG) intensities, relative to SiO(2), of approximately 0.25 ( = 0.28 pm/V) for the racemically twinned Zn(pyz)(H(2)O)(2)MoO(2)F(4) and approximately 1.0 ( = 0.55 pm/V) for the enantiopure Cd(pyz)(H(2)O)(2)MoO(2)F(4).

Journal Article↗
PubMed2002

Anionic templating: synthesis, structure, and characterization of novel three-dimensional mixed-metal oxychlorides Te(4)M(3)O(15).Cl (M = Nb(5+) or Ta(5+)).

Two new three-dimensional oxychlorides are reported, Te(4)M(3)O(15).Cl (M = Nb(5+) or Ta(5+)). The isostructural materials were synthesized by chemical transport reactions utilizing TeO(2), M(2)O(5), and MCl(5) (M = Nb(5+) or Ta(5+)) as reagents. The compounds exhibit a three-dimensional cationic tunnel framework, with Cl(-) anions occupying the tunnels. Crystal data: monoclinic, space group C2/c, a = 18.9944(7) A, b = 7.8314(3) A, c = 21.1658(8) A, beta = 116.6400(10) degrees, Z = 8 (T = 295 K).

Journal Article↗
PubMed2002

Structural modulation of molybdenyl iodate architectures by alkali metal cations in AMoO3(IO3) (A = K, Rb, Cs): a facile route to new polar materials with large SHG responses.

Three new molybdenyl iodates, KMoO3(IO3) (1), RbMoO3(IO3) (2), and CsMoO3(IO3) (3), have been prepared through the hydrothermal reactions of MoO3 with AIO4 (A = K, Rb, or Cs) at 180 C. These compounds are isolated as nearly colorless, air-stable crystals. Single-crystal X-ray diffraction experiments reveal that 1 possesses a corrugated layered structure constructed from molybdenum oxide chains that are bridged by iodate anions. The puckering of the layers is caused by the alignment of bent molybdenyl (MoO2(2+)) groups along one side of the molybdenum oxide chains. The K+ cations separate these layers from one another and serve to balance charge. In contrast, compounds 2 and 3, which are isostructural, form three-dimensional structures with small cavities filled with Rb+ or Cs+ cations. The differences between the structures of 1 and those of 2 and 3 are due to rotation of the molybdenyl units as translation occurs down the molybdenum oxide chains in order to accommodate the increased size of the Rb+ and Cs+ cations. This rotation allows for the iodate anions to bridge the molybdenum oxide chains in an additional dimension, creating a three-dimensional network structure. Furthermore, while 1 crystallizes in a centrosymmetric space group, 2 and 3 crystallize in polar space groups. Second-harmonic generation measurements on 2 and 3 show large responses of 400x alpha-quartz. Differential scanning calorimetry measurements demonstrate that 2 and 3 are thermally stable to 494 and 486 C, respectively. UV-vis diffuse reflectance spectra of these compounds show a high degree of transparency from 1 to 3 eV and a band gap of 3.1 eV.

Journal Article↗