Molten salt synthesis and structural charaterization of NaKMNbO5(M=La, Nd) and Na2K2M'4Nb2O13(M'=Gd, Sm)

• Main Author: 蔡明娟
• Other Authors: 廖儒修
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/22068134874762406828

碩士 === 國立中正大學 === 化學研究所 === 88 === The medium temperature solid state synthesis, using molten KOH/NaOH salt as a reaction medium and reactants are reported. Two novel layered metal oxides, NaKLaNbO5 and Na2K2Gd4Nb2O13, were synthesized with excellent yield. The structures were determined by X-ray diffraction techniques. NaKLaNbO5：tetragonal P4/nmm with a = 5.8135(4)Å, b = 5.8135(4)Å, c = 8.2804(4)Å, V = 279.85(3)Å3. Na2K2Gd4Nb2O13：monoclinic C2/c with a = 24.060(3)Å, b = 5.6464(6)Å, c = 11.181(1)Å, β = 116.40(2)°, V = 1360.6(3) Å3. The layered framework of NaKLaNbO5 is constructed by edge-sharing LaO8 cubes. NbO5 square pyramids located above and below the layers by edge-sharing of their four basal edges with the LaO8 cubes. K＋ and Na＋occupying the interlayered space. The structure of Na2K2Gd4Nb2O13 is closely related to that of NaKLaNbO5. This can be conceived readily by writing their chemical formula in more descriptive ways： Na2K2(La2O8)(NbO)2 and Na2K2(Gd4O11)(NbO)2. The former contains single layer of (La2O8) sandwiched by two layers of (NbO), while the latter has thicker slabs with double layered (Gd4O11) instead of (La2O8). High band gap semiconductors were found to be excellent heterogeneous catalysts for the decomposition of organic pollutants. The absorption surface area of the lamellar semiconductors can be increased by pillaring with silicates and Titanates. We report the intercalation and exfoliation behavior of KLaNb2O7 with a layered perovskite structure here. The cations in the interlayer space of KLaNb2O7 are easily to be exchanged. The d-spacing of LaNb2O7 has been intercalated with C18H37NH2 were 50.4Å. Porous Silica-pillared and Titania-pillared LaNb2O7 were prepare by dispersed Hx(CnH2n+1NH3)1-xLaNb2O7 in Si(OEt)4(TEOS), H2N(CH2)3Si(OEt)3 and Ti(OiPr)4, then calcined in air at 450 ℃. HLaNb2O7 has been exfoliated by 0.25∼1 equivalents of tetrabutylammonium hydroxide(TBAOH), resulting in LaNb2O7 nanosheet suspension. The photocatalytical properties of the compounds prepared above were also investigated.