Transmission Electron Microscopy Study of α-Decay Damage in Aeschynite and Britholite

1996 ◽  
Vol 465 ◽  
Author(s):  
W. L. Gong ◽  
L. M. Wang ◽  
R. C. Ewing ◽  
L. F. Chen ◽  
W. Lutze
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Rare Earth ◽  
Alpha Decay ◽  
High Resolution Electron Microscopy ◽  
Microscopy Study ◽  
Structure Type ◽  
Electron Microscopy Study ◽  
Α Decay ◽  
Transmission Electron

ABSTRACTThe aeschynite structure-type (Ce,Nd,La,Th,U,Ca)(Nb,Ti)2O6, and the rare-earth silicate apatite structure-type with the formula (Ce,La,Nd,Ca,Th)10(SiO4,PO4)6(O,F,OH)2 are important rare-earth and actinide host phases for high-level nuclear waste. Natural phases of these structure-types have calculated alpha-decay doses up to ∼1017 α-events/mg which have accumulated over hundreds of millions of years. Transmission electron microscopy has been used to study the microstructure of α-decay damage in aeschynite and britholite. Electron diffraction analysis of natural aeschynite revealed that minerals originally crystalline gradually lost their crystallinity with increasing alpha-decay doses. Helium bubbles were found in the aeschynite which have accumulated up to ∼2×1016 α-events/mg. These bubbles may nucleate within collision cascades during a-decay damage. Electron irradiation has an enhanced rare-gas migration and the formation of larger bubbles. High-resolution electron microscopy (HRTEM) revealed that amorphization during accumulation of a-decay damage was from alpha-recoil nuclei collision cascades, in both the aeschynite and britholite.

Transmission Electron Microscopy Study of Epitaxial Co/Au and Co/Pd (111) Multilayers

1992 ◽  
Vol 263 ◽  
Author(s):  
A.E.M. de Veirman ◽  
F. Hakkens ◽  
W. Coene ◽  
F.J.A. Den Broeder
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution Electron Microscopy ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Interface Plane ◽  
Misfit Dislocations ◽  
Transmission Electron Microscopy Study ◽  
Cross Sectional ◽  
Transmission Electron

ABSTRACTThe results of a transmission electron microscopy study of Co/Au and Co/Pd multilayers are reported. Special emphasis is put on the epitaxial growth and the relaxation of the misfit strain of these high misfit systems. In bright-field cross-sectional images, periodic contrast fringes are observed at the interfaces, which are the result of Moiré interference and which allow determination of the degree of misfit relaxation at the interface. It was established that 80-85% of the misfit is relaxed. From high resolution electron microscopy images the Burgers vector of the misfit dislocations was derived, being a/2<110> lying in the (111) interface plane. The results obtained for the Co/Au and Co/Pd multilayers will be discussed in comparison with those obtained for a bilayer of Co and Au.

A transmission electron microscopy study of the crystallinity and secondary phase formation in melt-processed YBa2Cu3O7−δ

1996 ◽  
Vol 11 (12) ◽  
pp. 2990-2999 ◽  
Author(s):  
Y. Yan ◽  
D. A. Cardwell ◽  
A. M. Campbell ◽  
W. M. Stobbs
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Secondary Phase ◽  
High Resolution Electron Microscopy ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Secondary Phase Formation ◽  
Layer Stacking

The microstructure of large grain melt-processed YBa2Cu3O7−δ containing 10 molar% excess Y2BaCuO5 prepared and oxygenated under atmospheric pressure has been investigated by transmission electron microscopy (TEM) and optical microscopy. These materials always contain parallel structural and microscopic platelet-like features in the crystallographic a-b plane of a few microns spacing which have been variously described as grain boundaries or microcracks. We have observed such features, which clearly influence the flow of current in melt-processed YBCO, to consist of copper deficient, impurity phase material which can be either amorphous or crystalline in nature. A variety of defects have been observed by high-resolution electron microscopy (HREM) in the vicinity of these platelet boundaries, including double and triple CuO layer stacking faults, which may constitute effective flux pinning sites.

Transmission electron microscopy study of Co/Pd and Co/Au multilayers

1993 ◽  
Vol 8 (5) ◽  
pp. 1019-1027 ◽  
Author(s):  
F. Hakkens ◽  
A. De Veirman ◽  
W. Coene ◽  
Broeder F.J.A. den
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
High Resolution Electron Microscopy ◽  
Microscopy Study ◽  
Columnar Structure ◽  
Electron Microscopy Study ◽  
Misfit Dislocations ◽  
Transmission Electron ◽  
Resolution Electron

The structure of Co/Pd and Co/Au (111) multilayers is studied using transmission electron microscopy and high resolution electron microscopy. We focused on microstructure, atomic stacking (especially at the interfaces), and coherency, as these are structural properties that have considerable magnetic effects. A columnar structure with a strong curvature of the multilayer influenced by substrate temperature during growth is observed. High resolution imaging shows numerous steps at the interfaces of the multilayer structure and the presence of misfit dislocations. In bright-field images, periodic contrast fringes are observed at these interfaces as the result of moiré interference. These moiré fringes are used to study the misfit relaxation at the interfaces, whereas electron diffraction gives the average relaxation over the whole layer. Both measurements determined that, for Co/Pd as well as Co/Au multilayers, 80–85% of the misfit is relaxed and 20–15% remains in the form of strain, independent of the Co layer thickness in the regime studied.

Transmission Electron Microscopy study of Bi-based superconducting phases

1990 ◽  
Vol 48 (4) ◽  
pp. 50-51
Author(s):  
J.G. Wen ◽  
K.K. Fung
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Single Crystals ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Space Groups ◽  
Superconducting Phases ◽  
Ceramic Samples ◽  
Transmission Electron ◽  
Modulated Structures

Bi-based superconducting phases have been found to be members of a structural series represented by Bi2Sr2Can−1Cun−1On+4, n=1,2,3, and are referred to as 2201, 2212, 2223 phases. All these phases are incommensurate modulated structures. The super space groups are P2/b, NBbmb 2201, 2212 phases respectively. Pb-doped ceramic samples and single crystals and Y-doped single crystals have been studied by transmission electron microscopy.Modulated structures of all Bi-based superconducting phases are in b-c plane, therefore, it is the best way to determine modulated structure and c parameter in diffraction pattern. FIG. 1,2,3 show diffraction patterns of three kinds of modulations in Pb-doped ceramic samples. Energy dispersive X-ray analysis (EDAX) confirms the presence of Pb in the three modulated structures. Parameters c are 3 0.06, 38.29, 30.24Å, ie 2212, 2223, 2212 phases for FIG. 1,2,3 respectively. Their average space groups are all Bbmb.

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