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The atomic structure at grain boundaries, the cause of low critical currents in sintered YBa2Cu3O7−δ
Abstracts of TheNetherlands Society of Electron Microscopy
point of view, has culminated in an unsurpassed, frantic, research activity. Virtually every conceivable measurement technique has been applied to these materials, by several different investigators operating in parallel, in order to establish their respective properties. Unfortunately, reproducibility and consistency of the data reported on the same variable is not always good, owing in part to the complex nature of these materials. Some basic phenomena and theoretical aspects associated with the superconducting state in general are treated briefly. Next, the new materials' properties (viz. compositional, structural, mechanical, electrical, etc.) are discussed. Their impact on our theoretical understanding, the possibilities for application and, in particular, how these properties affect the potential applicability of specific analytical methods is the main concern in the remainder.
Zandbergen
Gorlaeus Laboratories, State University L&den, P.O. Box 9502, 2300 RA Leiden, The Netherlands
THE ATOMIC STRUCTURE AT GRAIN BOUNDARIES, THE CAUSE OF LOW CRITICAL CURRENTS IN SINTERED YBa2Cu307_g * **, R. Gronsky**
High resolution electron microscopy (HREM) has been carried out on grain boundaries in dense (> 90%) YBa2Cu307-6, being both in the tetraqonal and orthorhombic form. It is discussed that the low critical currents in sintered materials are caused by preferred grain growth in combination with the atomic structure at the grain boundary interface, and by the intercalation near the grain boundary.
HREM INVESTIGATIONS OF DEFECTS SINTERED YBa2Cu307-S H.W.Zandbergen*
IN
** and G. Thomas**
of
Electron microscopy (HREM, ED and EDX) have been carried out on samples taken from a mixture during the synthesis of ZSM-5. The presence of a crystalline phase, present before the crystallization of ZSM-5, was observed. Evidence is obtained that this crystalline phase plays an important role in the nucleation of ZSM-5. If this is the case one would expect that the use of proper crystalline additives can enhance the crystallization of specific zeolites. By addition of a crystalline substrate to the reaction mixture a specific crystalline surface is supplied allowing the growth of zeolites with lattices, matching this crystalline substrate.
H.W. Zandbergen and G. Thomas**
*Gorlaeus Laboratories, State University Leiden, P.O.Box 9502, 2300 RA Leiden, The Netherlands, and National Center for Electron Microscopy, Materials and Chemical Sciences Division, Lawrence Berkeley Laboratory, Berkeley CA 94720, USA**
*Gorlaeus Laboratories, State University of Leiden, P.O. Box 9502, 2300 RA Leiden, The Netherlands; **National Center for Electron Microscopy, Materials and Chemical Sciences Division, Lawrence Berkeley Laboratory, BErkeley, CA 94720, USA
ELECTRON MICROSCOPIC STUDY OF THE NUCLEATION OF ZSM-5 CRYSTALS H.W.
221
YBa2Cu307_6 is studied using high resolution electron microscopy. Examples of the following defects are given: a planar stacking fault with a (CuO)2 double layer instead of a CuO layer; antiphase boundaries, characterized by a displacement of c/3, whereby the APB plane is (103) or (101); edge dislocations with Burgers vectors of a[OlOj, a[0011 and (a/Z+b/Z) 10011; [lo01 90' rotation twins; (110) mirror twins. The possible implications of these defects on the superconducting properties is discussed.
point of view, has culminated in an unsurpassed, frantic, research activity. Virtually every conceivable measurement technique has been applied to these materials, by several different investigators operating in parallel, in order to establish their respective properties. Unfortunately, reproducibility and consistency of the data reported on the same variable is not always good, owing in part to the complex nature of these materials. Some basic phenomena and theoretical aspects associated with the superconducting state in general are treated briefly. Next, the new materials' properties (viz. compositional, structural, mechanical, electrical, etc.) are discussed. Their impact on our theoretical understanding, the possibilities for application and, in particular, how these properties affect the potential applicability of specific analytical methods is the main concern in the remainder.
Zandbergen
Gorlaeus Laboratories, State University L&den, P.O. Box 9502, 2300 RA Leiden, The Netherlands
THE ATOMIC STRUCTURE AT GRAIN BOUNDARIES, THE CAUSE OF LOW CRITICAL CURRENTS IN SINTERED YBa2Cu307_g * **, R. Gronsky**
High resolution electron microscopy (HREM) has been carried out on grain boundaries in dense (> 90%) YBa2Cu307-6, being both in the tetraqonal and orthorhombic form. It is discussed that the low critical currents in sintered materials are caused by preferred grain growth in combination with the atomic structure at the grain boundary interface, and by the intercalation near the grain boundary.
HREM INVESTIGATIONS OF DEFECTS SINTERED YBa2Cu307-S H.W.Zandbergen*
IN
** and G. Thomas**
of
Electron microscopy (HREM, ED and EDX) have been carried out on samples taken from a mixture during the synthesis of ZSM-5. The presence of a crystalline phase, present before the crystallization of ZSM-5, was observed. Evidence is obtained that this crystalline phase plays an important role in the nucleation of ZSM-5. If this is the case one would expect that the use of proper crystalline additives can enhance the crystallization of specific zeolites. By addition of a crystalline substrate to the reaction mixture a specific crystalline surface is supplied allowing the growth of zeolites with lattices, matching this crystalline substrate.
H.W. Zandbergen and G. Thomas**
*Gorlaeus Laboratories, State University Leiden, P.O.Box 9502, 2300 RA Leiden, The Netherlands, and National Center for Electron Microscopy, Materials and Chemical Sciences Division, Lawrence Berkeley Laboratory, Berkeley CA 94720, USA**
*Gorlaeus Laboratories, State University of Leiden, P.O. Box 9502, 2300 RA Leiden, The Netherlands; **National Center for Electron Microscopy, Materials and Chemical Sciences Division, Lawrence Berkeley Laboratory, BErkeley, CA 94720, USA
ELECTRON MICROSCOPIC STUDY OF THE NUCLEATION OF ZSM-5 CRYSTALS H.W.
221
YBa2Cu307_6 is studied using high resolution electron microscopy. Examples of the following defects are given: a planar stacking fault with a (CuO)2 double layer instead of a CuO layer; antiphase boundaries, characterized by a displacement of c/3, whereby the APB plane is (103) or (101); edge dislocations with Burgers vectors of a[OlOj, a[0011 and (a/Z+b/Z) 10011; [lo01 90' rotation twins; (110) mirror twins. The possible implications of these defects on the superconducting properties is discussed.