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#1 07.04.2006 13:43:10

Марганафтика
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Реєстрація: 07.04.2006
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Ниобат кальция Са2Nb2O7

Коллеги!
Занимался ли кто-либо получением керамики из ниобата кальция?
каких условий протекания синтеза Вы придерживались?
Есть ли у керамики этого состава пьезоэлектрические свойства?
Буду рада любой информации по свойствам,синтезу этого вещества и ниобатов других щз металлов
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#2 07.04.2006 23:22:32

hsda
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Re: Ниобат кальция Са2Nb2O7

Марганафтика написав раніше:

Коллеги!
Занимался ли кто-либо получением керамики из ниобата кальция?
каких условий протекания синтеза Вы придерживались?
Есть ли у керамики этого состава пьезоэлектрические свойства?
Буду рада любой информации по свойствам,синтезу этого вещества и ниобатов других щз металлов
Заранее благодарна

Ловите ссылки на "calcium niobate" из ISI:

1. Almeida Silva, R., de Camargo, A. S. S., Cusatis, C., Nunes, L. A. O. and Andreeta, J. P. (2004). "Growth and characterization of columbite CaNb2O6 high quality single crystal fiber." Journal of Crystal Growth 262(1-4): 246-50.
         High optical and structural quality columbite CaNb2O6 single crystal was grown by laser-heated pedestal growth (LHPG) technique directly from starting reagents. The structural quality of the fibers was evaluated by X-ray rocking curve profile, X-ray phase contrast radiography and X-ray topography measurements whereas optical quality was characterized by optical microscopy and infrared to visible transmission measurements. Raman shifting and structural refinement of X-ray powder diffraction were used to check the formation of single phase CaNbO6. All results indicate that single phase, crack-free, colorless and transparent CaNb2O6 single crystal fiber was successfully obtained.

2. Ben Amor, R. and Zid, M. F. (2005). "NaCa1.5(NbO)(2)O-2(AsO4)(2)." Acta Crystallographica Section E-Structure Reports Online 61: I228-I30.
         The structure of the title compound, sodium calcium niobate oxide arsenate, NaCa1.5(NbO)(2)O-2(AsO4)(2), is built up from chains of NbO6 octahedra, parallel to the c axis, corner-sharing with AsO4. There are two types of AsO4 tetrahedron; one is connected to three different NbO6 octahedra, whereas the other is linked to two NbO6 octahedra only. The non-bonded O atoms point towards the inter-layer space where the sodium and calcium ions are located. A relationship between the structure of the title compound and the related Na3SbO(PO4)(2) (one-dimensional), Na2NbO2AsO4(two-dimensional) and NaVOAsO4 and SbOPO4 (three-dimensional) structures is discussed.

3. Carpy, A. and Portier, R. (1974). "Structural Study of Sodium Calcium Niobate Using Electron-Microscopy." Comptes Rendus Hebdomadaires Des Seances De L Academie Des Sciences Serie C 279(16): 691-6.
         
4. Freitas, L. and Ajersch, F. (1983). "The Chlorination Kinetics of Calcium Niobate." Cim Bulletin 76(854): 60.
         
5. Freitas, L. R. and Ajersch, F. (1986). "The Chlorination Kinetics of Calcium Niobate." Canadian Metallurgical Quarterly 25(3): 219-24.
         
6. Hardin, S., Hay, D., Millikan, M., Sanders, J. V. and Turney, T. W. (1991). "A Molecular Composite between Partially Hydrolyzed Aluminum Cations and a Layered Calcium Niobate Perovskite." Chemistry of Materials 3(5): 977-83.
         The layered perovskite (C4H9NH3)Ca2Nb3O10 with an interlayer spacing d001 = 2.51 nm reacts with solutions containing oligomeric aluminum hydroxycations to produce a single-phase, partly ordered composite material with an interlayer spacing d001 = 2.9 nm, which contracts to d001 = 2.0 nm on heating to 300-degrees-C.  Elemental analysis yields compositions in the range [Al1.67(OH)4(H2O)1.67][Ca2Nb3O10] to [Al3.06(OH)8.18(H2O)2.39]-[Ca2Nb3O10].  The materials decompose on heating, finally yielding a mixture of phases, including AlNbO4 and CaNb2O6, at 1200-degrees-C.  Thermogravimetric analysis, surface area measurements, XRD, electron diffraction, high-resolution TEM, and Nb-93 and Al-27 NMR studies suggest the presence of structurally unaltered Ca2Nb3O10 layers with an interlayer region "stuffed" by a layer of polymeric Al hydroxycations.

7. Kawakami, Y., Fukuda, M., Ikuta, H. and Wakihara, M. (1998). "Ionic conduction of lithium for perovskite type compounds, (Li0.05La0.317)(1-x)Sr0.5xNbO3, (Li0.1La0.3)(1-x)Sr0.5xNbO3 and (Li0.25La0.25)(1-x)M0.5xNbO3 (M=Ca and Sr)." Solid State Ionics 110(3-4): 187-92.
         In order to improve the ionic conductivity of lithium in the (Li, La)NbO3 perovskite system due to the expansion of the lattice, we attempted to prepare three perovskite compounds (Li0.05La0.317)(1-x)Sr0.5xNbO3, (Li0.1La0.3)(1-x)Sr0.5xNbO3 and (Li0.25La0.25)(1-x)Sr0.5xNbO3 by the substitution of larger Sr2+ ions for smaller Lif ions and La3+ ions in Li0.05La0.317NbO3 (orthorhombic), Li0.1La0.3NbO3 (tetragonal) and Li0.25La0.25NbO3 (cubic), respectively. Also, the perovskite compounds (Li0.25La0.25)(1-x)Ca0.5xNbO3 were prepared by the substitution of smaller Ca2+ ions for larger La3+ ions for comparison. The enhancement of lithium ionic conductivity was confirmed in all the Sr2+ doped perovskite compounds because of the increase of the cell volume. Especially, the perovskite (Li0.25La0.25)(1-x)Sr0.5xNbO3 exhibited marked improvement of ionic conductivity (x = 0.125, 7.3 x 10(-5) S.cm(-1) at 25 degrees C) compared with that of the other perovskites ((Li0.05La0.317)(1-x)Sr0.5xNbO3 and (Li0.1La0.3)(1-x)Sr0.5xNbO3), on the contrary, the ionic conductivity of (Li0.25La0.25)(1-x)Ca0.5xNbO3 perovskite compounds decreased with increasing the amount of calcium due to the decrease of the cell volume.

8. Merry, J. C., Leach, A. C. and Ubic, R. (2002). "Lead doped calcium niobate-tantalate pyrochlores: phase structure and dielectric properties." British Ceramic Transactions 101(4): 143-5.
         The microwave properties of lead pyroniobates have been shown to be influenced by their crystal structures. The incorporation of PbO rich layers as the concentration of Pb increases enables these materials to attain high Q(f) but this is offset by poor epsilon(r) and tau(f) performance. Isovalent doping of Ta5+ ions oil the niobium sites can reduce tau(f). In a similar previous study calcium niobate-tantalate with zero tau(f) was derived but both epsilon(r) and Q(f) ivere lower than for the lead pyroniobates. The present work aims to build on these findings by preparing pyrochlore ceramics simultaneously doped on both A and B sites, to give minimal tau(f) values and enhanced quality factors for medium permittivity applications. A single phase composition of (Ca1.4Pb0.6)(Nb0.5Ta1.5)O-7 was prepared by mixing precalcined batches of Ca-2(Nb0.5T1.5)O-7 and Pb-2(Nb0.5Ta1.5)O-7 in the appropriate ratio. Pellets ivere sintered to high densities and their dielectric properties tested. Preliminary data suggest that compositions with greater lead content and higher A/B cation ratio should be pursued.

9. Raghavan, S. (1991). "Thermodynamic Stability of Mono-Calcium Niobate Using a Calcium-Fluoride Solid Electrolyte Galvanic Cell." Transactions of the Indian Institute of Metals 44(3): 285-6.
         
10. Treacy, M. M. J., Fisher, M. E. and Jacobson, A. J. (1995). "A Hollow-Cone Dark-Field Study of Interlayer Cracks in Delaminated Hca2nan-3nbno3n+1 Materials." Philosophical Magazine a-Physics of Condensed Matter Structure Defects and Mechanical Properties 72(1): 161-77.
         We investigate the blister features that appear in small-angle hollow-cone dark-field images of overlapping layers of delaminated calcium niobate. Modelling shows that the blister contrasts are caused by pockets of gas or liquid that have become trapped when calcium niobate layers are brought into contact and reseal. Hollow-cone dark-field contrast is primarily due to diffraction variations caused by sheet bending around the pressurized cracks.
         
11.  Husson E., Dao N. Q. "Study on Polarized Raman-spectrum of Calcium Niobate." (1974) Comptes Rendus Hebdomadaires des Seances de l'Academie des Sciences Serie C 279 (4): 141-43.
       
12.  Aubree J. (1971) "Pulling of Neodymium-doped Monocrystalline Calcium Niobate." Journal of Crystal Growth 13 : 675.
         
13.  Ballman A. A., Porto S. P. S., Yariv A. (1963) "Calcium Niobate Ca(NbO3)2 - a New Laser Host Crystal." Journal of Applied Physics 34 (11): 3155.

#3 10.04.2006 10:28:25

Марганафтика
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Реєстрація: 07.04.2006
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Re: Ниобат кальция Са2Nb2O7

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