scholarly journals Electron microscopy study of microsegregation and defects in Czochralski grown calcium gallium germanium garnet single crystals

1978 ◽  
Author(s):  
T.F. Roth
Keyword(s):  
Electron Microscopy ◽  
Single Crystals ◽  
Microscopy Study ◽  
Electron Microscopy Study

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.

Electron Microscopy Study of Fatigue Crack Initiation in Ni3Al Single Crystals

1988 ◽  
Vol 133 ◽  
Author(s):  
L. M. Hsiung ◽  
N. S. Stoloff
Keyword(s):  
Electron Microscopy ◽  
Fatigue Crack ◽  
Crack Initiation ◽  
Single Crystals ◽  
Room Temperature ◽  
Fatigue Crack Initiation ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Dislocation Loops ◽  
Defect Clusters

ABSTRACTTransmission electron microscopy of single-slip oriented Ni3Al single crystals cyclically deformed at room temperature revealed a high density of dislocation dipoles and point defect clusters. The majority of the defect clusters were identified by weak-beam TEM to be of vacancy type. The observations of circular perfect dislocation loops, Frank loops, and spherical voids revealed the evidence of vacancy condensation during fatigue cycling at room temperature. Together with SEM observations of surface topography, it is suggested that fatigue crack initiation in Ni3Al single crystals can be rationalized by formation of microvoids at PSB/matrix interfaces.

Electron microscopy study of Pb-substitution in bulk Bi–Sr–Ca–Cu–O superconductors

1989 ◽  
Vol 4 (4) ◽  
pp. 748-751 ◽  
Author(s):  
D. J. Werder ◽  
C. H. Chen ◽  
S. Jin ◽  
R. C. Sherwood
Keyword(s):  
Electron Microscopy ◽  
Single Crystals ◽  
Structural Model ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Lattice Parameters ◽  
Modulated Structure ◽  
Pb Substitution

We present the results of an electron microscopy study of Pb-substitution in bulk Bi–Sr–Ca–Cu–O superconductors. We observe grains with c-axis lattice parameters of 30.8 Å (2212 phase), 36.7 Å (2223 phase), and 43.2 Å (2234 phase) containing no intergrowth defects. The existence of two separate incommensurate superstructures, Q1 and Q2, which were previously observed in Pb-doped ceramics and single crystals, has been confirmed in this study. It is found that superlattice reflections from the Q2,-modulated structure in the 2223 phase are much weaker than those from the Q2-modulation, whereas the diffraction intensities of the Q1- and Q2-modulations in the 2212 phase are similar. We also show that the periodicity along the b-axis of the Q2-modulation increases with increasing Pb-substitution, contrary to the implications of a previously suggested structural model.

Surface morphology of PrBa2Cu3O7-δ single crystals after the long-lasting high-temperature reduction

Open Physics ◽  
2003 ◽  
Vol 1 (4) ◽  
Author(s):  
Maciej Łuszczek ◽  
Wojciech Sadowski
Keyword(s):  
Electron Microscopy ◽  
High Temperature ◽  
Single Crystals ◽  
Crystal Surface ◽  
Microscopy Study ◽  
Structural Transformations ◽  
Electron Microscopy Study ◽  
Time Dependent ◽  
Decomposition Products ◽  
Scanning Electron

AbstractThe results of the detailed scanning electron microscopy study of PrBa2Cu3O7-δ single crystals after the long-lasting high-temperature post-growth treatment are reported. The presence of the unstable decomposition products on the crystal surface indicates that the onset of superconductivity must be related to the structural transformations in the bulk (approximately 20% of the total volume of the examined crystals). The time-dependent character of the superconductivity in the Pr-123 crystals could be attributed to the migration of defects in the Pr−Ba sublattice from the bulk toward the surface.

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