CERAMICS – Silikáty (DOC download) by forrests

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									CERAMICS – Silikáty
Číslo 1/2005 – abstrakta

Water-induced and Co-filling kontrol induced ferromagnetism in Rb2Ni3S4 Katsuhiro Hondou1, Manabu Usuda*, Katsunori Iio Dept. of Phys., Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 1528551, Japan *Synchrotron Radiation Rearch Center, Japan Atomic Energy Research Institute, Spring-8, Mikazuki, Hyogo 679-5148, Japan 1 Present address: Shiga International Patent Office, 2-3-1 Yaesu, Chuo-ku, Tokyo 104-8453, Japan E-mail: khondou@lee.phys.titech.ac.jp; hondo@shigapatent.com Submitted November 1, 2004; accepted December 21, 2004

Keywords: Magnetic susceptibility, Electric resistivity, Chalcogenide; (NiS4) Square plane; Kagome lattice The influence of water-immersing on the magnetic behavior of Rb2Ni3S4 single crystals grown by the flux method was studied, where the intrinsic substance is non-magnetic because of the low spin state of Ni2+ in a Kagome lattice. The influence of Co-doping to Rb2Ni3S4 was also studied in terms of the local spin density approximation (LSDA) band structure calculation. Residual ferromagnetic moments appeared in specimens immersed into water, as their magnitudes increase depending on the immersion time. The LSDA band structure calculation suggested that Co substitution for Ni allows deriving a novel ferromagnetic behavior.

Crystallization Behavior and Phase Relations of H-MOD Derived Thin Films Based on Barium Sodium Niobates Junhui Lou, Hee Young Lee, Joon-Hyung Lee*, Jeong-Joo Kim*, Sang-Hee Cho* Department of Materials Science and Engineering, Yeungnam University, Gyeongsan 712749, Korea *Department of Inorganic Materials Engineering, Kyungpook National University, Daegu 702-701, Korea E-mail: hyulee@yu.ac.kr Submitted September 17, 2004; accepted November 3, 2004

Keywords: Tungsten bronze structure, BNN, Ferroelectric thin film, H-MOD Ba2NaNb5O15, hereafter called BNN, thin film is an attractive candidate for such applications as nonvolatile memory and electro-optic devices. BNN thin films of about 450nm thickness that have different contents of Ba, Na and Nb have been prepared by hybrid metalorganic decomposition, hereafter called H-MOD, process using bare and platinized Si wafers as substrate. XRD and FE-SEM measurements were used to investigate the phase evolution behavior and the microstructure of the films. It was found that Nb content strongly influenced the phase formation of the films, where BaNb2O6 phase was always formed at the stoichiometric BNN composition. However, the amount of BaNb2O6 phase decreased with the increase of excess Nb content, and the thin film with single phase orthorhombic tungsten bronze structure was obtained at the temperature as low as 750°C.

Microstructure Evolution and Electrical Properties of Ba2NaNb5O15 and BaTiO3 Composites Myoung-Sup Kim, Joon-Hyung Lee, Jeong-Joo Kim, Hee Young Lee*, Sang-Hee Cho Department of Inorganic Materials Engineering, Kyungpook National University, Daegu 702701, Korea *Department of Materials Science and Engineering, Yeungnam University, Gyeongsan 712749, Korea E-mail: jjkim@knu.ac.kr Submitted September 17, 2004; accepted December 12, 2004

Keywords: Ferroelectrics, Composite, BNN-BT, Sintering, Dielectric characteristics Phase development and sintering behavior and dielectric characteristics of the composites of tungsten bronze structured Ba2NaNb5O15 (BNN) and perovskite structured BaTiO3 (BT) were examined as a function of molar ratio x in (1-x)Ba2NaNb5O15-xBaTiO3. A wide range of solid solution of BT in BNN was observed up to x=0.4~0.6, and the lattice constants increased with BT contents. Since the solid solution of BT expelled Na ions from BNN, liquid phase with excess Na might be produced during sintering and resulted in accelerated densification and abnormal grain growth. More BT addition in BNN over the solubility limit produced a second phase of Ba6Ti7Nb9O40 together with BT, and those phases played a role as grain growth inhibitors. The Curie temperature (TC) and the maximum dielectric constant of BNN decreased as the content of BT increased. Besides, when BNN is added to BT, the solubility limit of BNN in BT was very narrow compared to the case of BT addition to BNN, which resulted in the generation of Ba6Ti7Nb9O40 second phase. The addition of BT to BNN also shifted the TC to lower temperature. In the case of x=0.6, two dielectric relaxation peaks were observed which is believed due to the coexistence of BNN and BT in the sample.

YBa2Cu3O7-x MELT-TEXTURED THICK FILMS DEPOSITED ON ALUMINATOUGHENED ZIRCONIA SUBSTRATE Gustav PLESCH, Juraj KLIMENT, Peter BILLIK, Alexander CIGÁŇ*, Ján MAŇKA* , Julian PLEWA**, Horst ALTENBURG** Department of Inorganic Chemistry, Faculty of Natural Sciences, Comenius University, 842 15 Bratislava, Slovakia *Institute of Measurement Science, Slovak Academy of Sciences, 841 04 Bratislava, Slovakia **FH Münster / University of Applied Sciences, Lab. Supraleitung, Keramik, Kristalle, SIMa, Steinfurter Initiative für Materialforschung, Steinfurt, Germany E-mail: plesch@fns.uniba.sk Submitted September 17, 2004; accepted November 10, 2004

Keywords: YBa2Cu3O7 (YBCO), Thick films, Melt textured, Alumina toughened YSZ substrate Melt textured superconducting YBCO films with an approximate thickness of 50-120 µm and Tc(0) values ranging between 86.5 and 88.5 K have been prepared on polycrystalline yttria-stabilized zirconia substrate, toughened by 20 wt.% Al2O3. Between the substrate and superconducting film an interface layer was formed. Their AC and DC magnetization characteristics were measured and the values of the magnetic penetration field Hp1 were estimated. The penetration field Hp1 of 2.7 kA m-1 was obtained for the thinner film deposited with a higher spin coating rate, while for the thicker film deposited with a lower spin coating rate Hp1 = 4.4 kA m-1. Repeated temperature cycling between room and liquid nitrogen temperatures and corresponding measurement of the magnetization hysteresis curves reveal the significant decrease of the grain superconducting pro-perties caused probably by arising cracks.

EFFECTS OF POST-OXYGEN ANNEALING AND LANTHANUM DOPING ON INTERAND INTRA-GRAIN PROPERTIES OF (Tl,Pb)-1223 SUPERCONDUCTORS ALEXANDER CIGÁŇ, GUSTAV PLESCH*, JÁN MAŇKA, FRANTIŠEK HANIC, MICHAL KOPČOK, ANTON KOŇAKOVSKÝ, JURAJ KLIMENT* Institute of Measurement Science, Slovak Academy of Sciences, Dúbravská cesta 9, 841 04 Bratislava, Slovakia *Department of Inorganic Chemistry, Faculty of Natural Sciences, Comenius University, 842 15 Bratislava, Slovakia E-mail: alexander.cigan@savba.sk Submitted September 17, 2004; accepted November 3, 2004

Keywords: (Tl,Pb)-1223 based superconductors, La3+ doping, Magnetization, SQUID gradiometer, Ageing Effects of oxygen annealing and low level La3+ doping of the (Tl,Pb)-1223 system have been investigated. Samples with the nominal composition (Tl0.6Pb0.5)(Sr0.8Ba0.2)2Ca2Cu3O8+ - x LaO1.5, where x ranges from 0.00 to 0.10, were synthesized using a sol-gel process. Their superconducting inter- and intra-grain properties, phase compositions, and microstructure were stu-died. XRD results prove that (Tl,Pb)-1223 is the dominant phase in all samples. The La doping initiates a formation of the (Tl,Pb)-1212 phase and decreases the volume superconducting properties. The post oxygen annealing strongly improves intergrain superconducting links and leads to a positive effect on the critical temperature, Tcon and the DTcon. The central peak of magnetization hysteresis loops around zero field is found to be in an anomalous positive position on the descending branch of the external field.

Synthesis, structure and conductivity of layered perovskites Nikolay Velinov, Nadezhda Brashkova, Vladimir Kozhukharov University of Chemical Technology and Metallurgy, 8 Kliment Okhridski blvd., 1756 - Sofia, Bulgaria E-mail: nikivelinov@abv.bg Submitted September 13-17, 2004;accepted November 16, 2004

Keywords: Layered perovskites, Ruddlesden-Popper phase, Conductivity By using the nitrate-citrate method we have been able to synthesize layered perovskites from the Ruddlesden-Popper (R-P) phases (LaSr)n+1FenO3n+1, where n = 1, 2, 3. In this paper we present the results about their thermal evolution during the wet-chemical synthesis, structural and microstructural characterization by means of thermogravimetry/ differential thermal analysis, X-ray diffraction and scanning electron microscopy. By measuring the total conductivity, using 4-probe DC method an attempt to correlate structure and conductivity of layered perovskites has been made. We established that at temperature over 140°C electrical conductivity of triple layer LaSr3Fe3O10 perovskite is significantly higher compared with these of single and double layer compounds. The materials possess potentially applicable mixed electron-ion conductivity and catalytic activity, as well.

THE INFLUENCE OF THE PREFERRED ORIENTATION OF BOEHMITE CRYSTALLITES ON -Al2O3 CRYSTALLIZATION KATARÍNA BODIŠOVÁ, LADISLAV PACH, VLADIMÍR KOVÁR Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, 81237 Bratislava, Slovakia E-mail: katarina.bodisova@stuba.sk Submitted September 13-17, 2004; accepted November 19, 2004 Keywords: Sol-gel, Boehmite, Silica, Particle arrangement, -Al2O3, Crystallization Monolithic boehmite gels were prepared from commercial peptizable Condea product. The gels were modified by nanoparticle SiO2 addition. Preferred orientation of boehmite crystallites in the gels and phase composition of sintered samples was observed by XRD analysis. To determine the effect of gel structure and eventually of SiO2 addition on sintering and crystallization DTA, SEM and bulk density measurement were used. Boehmite crystallites align themselves spontaneously during gelation into preferred orientation state that can be avoided by ultrasonication or by the nanoparticle SiO2 addition. The ordered or disordered gel microstructure has only marginal influence on high-temperature processes (crystallization, sintering). These processes are significantly influenced by addition of foreign SiO2 nanoparticles, which decrease coordination of boehmite particles suppressing thus Al2O3 nucleation. Spread of SiO2 on the surface of Al2O3 particles inhibits -Al2O3 crystallization up to 1350°C.

PREPARATION AND CHARACTERIZATION OF BOEHMITE, CuO, TiO2 AND Nb2O5 BY HYDROTHERMAL ASSISTED SOL-GEL PROCESSING OF METAL ALKOXIDES Mahdi Mirzaee, Mostafa M. Amini, Mahdi Sadeghi, Farnaz Yeganeh Mousavi, Maasomeh Sharbatdaran Department of chemistry, Shahid Beheshti University, Tehran 198396311, Iran E-mail: m-pouramini@cc.sbu.ac.ir Submitted September 17; accepted December 27, 2004

Keywords: Hydrothermal, Boehmite, Sol-gel, Metal alkoxide, Copper oxide, Titanium oxide, Niobium oxide Conventional and hydrothermally assisted sol-gel processing have been used to synthesis of monodispersed nanosize boehmite, copper, titanium and niobium oxides from

their alkoxides. The prepared powders have been characterized by X-ray diffraction (XRD), thermal analysis (TGA/DSC) and scanning electron microscopy (SEM). XRD, infrared spectroscopy (IR) and thermal analysis showed that the degree of crystallization of boehmite, prepared by hydrothermally assisted sol-gel processing from aluminum 2-butoxide, increases by increasing processing temperature. Pure tenorite phase was formed in either conventional or hydrothermally assisted sol-gel processing from copper 2-pyridylethoxide. Conventional sol-gel processing of titanium oxide from titanium 2-ethoxyethoxide resulted to formation of a mixture of rutile and anatase phases, whereas hydrothermally assisted sol-gel processing ends up to formation of pure anatase phase. Single phase Nb2O5 is formed in either conventional or hydrothermally assisted sol-gel processing from niobium 2-ethoxyethoxide. Scanning electron microscopy (SEM) revealed spherical, nanosize and homogenous particles for the oxides prepared by hydrothermally assisted sol-gel processing.

CONDITIONS OF SYNTHESIS OF Co-Zn-Ti-Cr SPINEL PIGMENT ŽANETA MESÍKOVÁ, MIROSLAV TROJAN, PETRA ŠULCOVÁ Department of Inorganic Technology, Faculty of Chemical Technology, University of Pardubice, nám. Čs. Legií 565, 532 10 Pardubice, Czech Republic E-mail: zaneta.mesikova@upce.cz Submitted September 17, 2004; accepted November 25, 2004

Keywords: Ceramic pigments, High-temperature pigments, Spinel The main aim of the research was to propose, verify and analyze the conditions of synthesis of spinel pigment Co0.46Zn0.55(Ti0.064Cr0.91)2O4. The influences of the raw materials and the calcinate temperature on the colour properties of the prepared pigments were monitored. These pigments afford interesting green hue in ceramic glazes and in organic matrix. Mean particle sizes of the prepared pigments decreased after milling from values around 24 µm to 1.5 µm. The analysis of the X-ray diffraction patterns established that all the samples have a single phase cubic spinel structure. Some of the physical-chemical properties that characterize the prepared pigments (specific weight, oil number, CPVC) were also determined.

Planar optical waveguides in newly developed Er:silicate glasses: A comparative study of K+ and Ag+ ion exchange Linda Salavcová, Blanka Švecová, Stanislava Janáková*, Ondřej Kolek*, Martin Míka*, Jarmila Špirková, Anna Langrová** Department of Inorganic Chemistry, Institute of Chemical Technology Prague, Technická 5, 166 28 Prague, Czech Republic *Department of Glass and Ceramics, Institute of Chemical Technology Prague, Technická 5, 166 28 Prague, Czech Republic **Institute of Geology, Czech Academy of Science, Rozvojová 135, 165 02 Prague, Czech Republic E-mail: linda.salavcova@vscht.cz Submitted September 17, 2004; accepted December 17, 2004

Keywords: Silicate glass, Erbium, Optical waveguides, Ion exchange Materials containing laser-active ions (e.g. erbium and other rare earths) in combination with planar optical waveguides technology are being recently investigated in order to obtain optical amplifying or lasing structures for photonics applications. This contribution reports about fabrication of optical waveguides in newly designed silicate glass substrates by ion exchanges (IE) K+  Na+ and Ag+  Na+. The content of erbium and sodium in these glasses was kept constant while the ratio of glass intermediates, MgO, CaO and ZnO differed. The optical properties´ characterisation of the fabricated layers (i.e. number of modes and refractive index profile) was performed by dark mode spectroscopy at 671 nm. Another important information on depth of the optical layers was obtained by polarising optical microscope. Concentration depth profiles of the exchanged ions were analysed by scanning electron microscopy. Special attention was paid to possibility of Er ions migration during the fabri-cation process. The Ag+ exchange proceeds with much higher velocity than the K+ one and provides optical layers with more or less step-like refractive index profiles. On the other hand the K+ waveguides have graded shape of these profiles with much smaller refractive index increment (approx. 0.009) compared with Ag+ ones (approx. 0.09) and relatively high TE-TM birefringence. Neither difference in Er ions distribution nor microcluster formation was observed (being under the detection limit). The results are discussed from the point of view of the glass matrix permeability for the exchanged ions and potential applications of both types of the waveguides.

Luminescence properties of Eu2+ doped dibarium magnesium disilicate, Ba2MgSi2O7:Eu2+ Tuomas Aitasalo, Jorma Hölsä, Taneli Laamanen, Mika Lastusaari, Laura Lehto, Janne Niittykoski, Fabienne Pellé* University of Turku, Department of Chemistry, Laboratory of Inorganic Chemistry, FI-20014 Turku, Finland Graduate School of Materials Research, Turku, Finland *CNRS, UMR 7574, ENSCP, Laboratoire de Chimie Appliquée de l'Etat Solide, 11, r. P. et M. Curie, F-75231 Paris cedex 05, France E-mail: japeni@utu.fi Submitted September 17, 2004; accepted November 19, 2004 Keywords: Dibarium magnesium disilicate, Europium, Persistent luminescence A new persistent luminescence material, monoclinic Ba2MgSi2O7:Eu2+, was prepared by a solid state reaction. Both the UV excited and persistent luminescence are observed at the green region centred at 505 nm. Both luminescence phenomena are due to the same Eu2+ ion occupying the single Ba2+ site in the lattice. The R3+ co-doping (R is rare earth) usually enhances the persistent luminescence of Ba2MgSi2O7:Eu2+. Especially, the Tm3+ ion has a very strong effect. Two thermoluminescence peaks at 90 and 130°C are observed in the glow curve of Ba2MgSi2O7:Eu2+, which is nearly ideal for a persistent luminescence material. The persistent luminescence is probably due to lattice defects i.e. oxygen (cation) vacancies, which create trapping levels for electrons (holes). Recombination of the electron-hole pair and energy transfer to the Eu2+ ion complete the probable persistent luminescence mechanism. The details of the mechanism(s) need, however, more experimental work to be carried out. The stable disilicate materials are very good candidates for the persistent luminescence materials as alternatives to the Eu2+ doped alkaline earth aluminates.

EFFECTS OF PREPARATION PROCESS ON DECAY LIFETIME OF LaPO4:Ce,Tb PHOSPHORS Yunxia Yang, Chen Li, Shuanglong Yuan, Bin Fang, Guorong Chen Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237, China E-mail: grchen@ecust.edu.cn Submitted September 17, 2004; accepted January 13, 2005

Keywords: LaPO4:Ce,Tb phosphor, Preparation, Decay

A two-step reaction method was used to prepare superfine LaPO4:Ce,Tb phosphor particles under two set of conditions. The crystallinity and particle morphology of the product were characterized by using XRD, SEM and particle size analysis, and decay lifetime was investigated as a function of preparation conditions. Results highlighted that an appropriate preparation process leads to less-aggregated LaPO4:Ce,Tb phosphor with greatly improved decay lifetime.

TRANSFORMATION OF NITRATE ION INTO PEROXIDE UNDER IRRADIATION Vladimir Anan'ev, Mikhail Seliverstov Department of Analytical Chemistry, Kemerovo State University, Krasnaya 6, 650043, Kemerovo, Russia E-mail: eprlab@kemsu.ru Submitted September 17, 2004; accepted December 16, 2004

Keywords: Point defects, Optical spectra, Peroxynitrite, radiolysis, Alkali nitrate crystals, Ion-molecular crystals Different types of point defects formed in ion-molecular crystals have been described. Based on the data on radiation-induced optical spectra of alkali nitrate crystals peroxynitrite was stated to be one of these defects. The peculiarities of the formation of defects in ionmolecular crystals have been interpreted in relation to the structure of energy bands of these crystals.


								
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