Degradation of high-Tc superconductors by annealing in dry and moist atmospheres

A study is made of the effects of annealing both La2−xSrxCuO4 (for x = 0, 0.1, and 0.15) and YBa2Cu3O7 in wet and dry O2 atmospheres at various temperatures between 200 and 930 °C. In the case of La2−xSrxSrCuO4, substantial degradation of resistive properties occurs during annealing in moist O2, the degradation being highest at 200 °C and decreasing as the treatment temperature increases. Since the Meissner effect remains unaffected, it is concluded that degradation is due to the formation of a hydroxide species at grain boundaries, which decomposes as the anneal temperature is increased to 930 °C. In the case of YBa2Cu3O7, on the other hand, moisture does not produce degradation for anneals at 200 °C and above, but severe degradation of resistive behavior does occur for dry O2 anneals, with a maximum effect at 500 °C. It is found that this effect results from a contaminant gas, possibly CO2, absorbed by the furnace when it is open to air. Again, the degradation is due to formation of a grain-boundary phase which decomposes by annealing at 930 °C.

Download Full-text

Measurement of the Displacement Across a Coincidence Grain Boundary

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100078213 ◽

1977 ◽

Vol 35 ◽

pp. 124-125

Author(s):

J. W. Matthews ◽

W. M. Stobbs

Keyword(s):

Grain Boundary ◽

Grain Boundaries ◽

Stacking Fault ◽

The Other ◽

Measuring Technique ◽

High Angle ◽

Twin Boundaries ◽

Rigid Displacement ◽

Cubic Crystals ◽

Lattice Displacement

Many high-angle grain boundaries in cubic crystals are thought to be either coincidence boundaries (1) or coincidence boundaries to which grain boundary dislocations have been added (1,2). Calculations of the arrangement of atoms inside coincidence boundaries suggest that the coincidence lattice will usually not be continuous across a coincidence boundary (3). There will usually be a rigid displacement of the lattice on one side of the boundary relative to that on the other. This displacement gives rise to a stacking fault in the coincidence lattice.Recently, Pond (4) and Smith (5) have measured the lattice displacement at coincidence boundaries in aluminum. We have developed (6) an alternative to the measuring technique used by them, and have used it to find two of the three components of the displacement at {112} lateral twin boundaries in gold. This paper describes our method and presents a brief account of the results we have obtained.

Download Full-text

Doping induced enhancement of the critical currents of grain boundaries in high-Tc superconductors

Physica C Superconductivity ◽

10.1016/s0921-4534(00)00955-2 ◽

2000 ◽

Vol 341-348 ◽

pp. 1393-1396 ◽

Cited By ~ 11

Author(s):

J. Mannhart ◽

H. Bielefeldt ◽

B. Goetz ◽

H. Hilgenkamp ◽

A. Schmehl ◽

...

Keyword(s):

Grain Boundaries ◽

Critical Currents ◽

High Tc Superconductors ◽

High Tc

Download Full-text

Interaction of Abrikosov vortex with grain boundaries near Hc1. II. Magnetic and transport properties of polycrystalline high-Tc superconductors

Low Temperature Physics ◽

10.1063/1.1925347 ◽

2005 ◽

Vol 31 (5) ◽

pp. 371-377

Author(s):

L. V. Belevtsov

Keyword(s):

Grain Boundaries ◽

Transport Properties ◽

Abrikosov Vortex ◽

High Tc Superconductors ◽

High Tc

Download Full-text

Ac Susceptibility Studies of the High Tc Superconductors: Dissipative Effects in La2.xSrxCuO4-Y and YBa2Cu3O7-Y Systems

MRS Proceedings ◽

10.1557/proc-169-947 ◽

1989 ◽

Vol 169 ◽

Author(s):

Xinsheng Ling ◽

M. E. Filipkowski ◽

E. K. Heller ◽

J. I. Budnick

Keyword(s):

Grain Boundaries ◽

Order Parameter ◽

Ac Susceptibility ◽

Similar Process ◽

Charge Carrier Density ◽

High Tc Superconductors ◽

High Tc ◽

Spatial Fluctuation ◽

Dissipative Effects ◽

Ceramic Samples

AbstractWe have studied the variation of dissipative effects with doping in the high Tc superconductors La2-xSrxCuO4-y and YBa2Cu3O7-y by studying the lossy component of ac susceptibility as a function of temperature. We find relatively strong excess losses at low temperature in both systems, which indicate stronger flux creep at grain boundaries, in lower level doped ceramic samples produced by a similar process. This effect is more significant in the La2-xSrxCuO4-y (214) system than in the YBa2Cu3O7-y(123) system. We suggest that the microscopic mechanisms of weakening of the order parameter in the grain boundaries may be different in the two systems. In the 214 system, as the charge carrier density in the CuO2 planes is reduced, the spatial fluctuation of the order parameter in the CuO2 planes is enhanced. In the 123 system, the initial removal of O from the sample, which weakens the coupling between planes and increases the spatial fluctuation of the order parameter between CuO2 planes. The grain boundaries are degraded in both systems. The degradation in the 214 samples is more significant than in the 123 samples.

Download Full-text

Dynamical Simulation of the Motion of Curved Grain Boundaries Composed of Pyramidal-Shaped Ledges

MRS Proceedings ◽

10.1557/proc-193-189 ◽

1990 ◽

Vol 193 ◽

Cited By ~ 1

Author(s):

Re-Jhen Jhan ◽

P. D. Bristowe

Keyword(s):

Grain Boundary ◽

Grain Boundaries ◽

Boundary Migration ◽

Model System ◽

The Other ◽

Grain Boundary Migration ◽

Dynamical Simulation ◽

Atomic Mechanism ◽

Or Groups

ABSTRACTA dynamical simulation of curved grain boundaries composed of pyramidal-shaped ledges has shown that the boundaries can move by local conservative shuffles of atoms or groups of atoms such that one adjoining crystal grows at the expense of the other. In the model system studied, the shuffles often take the form of correlated rotational displacements about the axis normal to the boundary. The simulations provide support for the atomic mechanism proposed by Babcock and Balluffi to explain their observation of grain boundary migration without the participation of SGBDs.

Download Full-text

GRAIN BOUNDARIES: PHASE TRANSITIONS AND CRITICAL PHENOMENA

International Journal of Modern Physics B ◽

10.1142/s0217979291001176 ◽

1991 ◽

Vol 05 (19) ◽

pp. 2989-3028 ◽

Cited By ~ 53

Author(s):

E.I. RABKIN ◽

L.S. SHVINDLERMAN ◽

B.B. STRAUMAL

Keyword(s):

Phase Transitions ◽

Grain Boundary ◽

Grain Boundaries ◽

Critical Phenomena ◽

External Surface ◽

Theoretical Models ◽

Boundary Structure ◽

Boundary Phase ◽

Recent Experimental Data ◽

Grain Boundary Structure

Recent theories of grain boundary structure have been reviewed briefly. The possibility of existence of the same variety of phase transitions on grain boundaries as that on the crystal external surface has been demonstrated. Recent experimental data and theoretical models concerning grain boundary phase transitions are critically analysed. Grain boundary phase transitions connected with the formation of thin disordered layers on the boundary (prewetting, premelting) are particularly distinguished. Results of recent indirect experiments, which may be treated in terms of prewetting and premelting, have been reviewed. Experimentally observed critical phenomena in the vicinity of the prewetting transition on the tin-germanium interphase boundary have been discussed in terms of the critical exponents theory. Some ideas regarding directions of further research are presented.

Download Full-text

The Morphology of Grain Boundary Interactions with Twins in YBa2Cu3O7−δ

MRS Proceedings ◽

10.1557/proc-319-227 ◽

1993 ◽

Vol 319 ◽

Author(s):

Jenn-Yue Wang ◽

A. H. King

Keyword(s):

Grain Boundary ◽

Grain Boundaries ◽

Twin Boundary ◽

Interfacial Energy ◽

Coincidence Site Lattice ◽

The Other ◽

Twin Boundaries ◽

Site Lattice ◽

Dislocation Arrays

AbstractVarious morphologies are observed where twins meet grain boundaries in YBa2Cu3O7−δ. Twins may be “correlated” at the boundary (i.e. twin boundaries from one grain may meet a twin boundary from the other grain in a quadruple junction) and the twins may be narrowed or “constricted” at the boundary. These effects are determined by the interfacial energy. We estimate the energy of the various interfaces by determining the dislocation arrays they contain, using the constrained coincidence site lattice (CCSL) model and Bollmann's O2-lattice formalism. Our approach indicates that there are significant changes in the energy of the interfaces and is thus able to explain the variety of observed morphologies.

Download Full-text

Grain Boundary Phase Analysis of Silicon Nitride by a Newly Developed 300kv Field-Emission Electron Microscope

MRS Proceedings ◽

10.1557/proc-346-733 ◽

1994 ◽

Vol 346 ◽

Cited By ~ 2

Author(s):

Y. Bando ◽

H. Suematsu ◽

M. Mitomo

Keyword(s):

Electron Microscope ◽

Silicon Nitride ◽

Grain Boundary ◽

Grain Boundaries ◽

Phase Analysis ◽

Field Emission ◽

Boundary Phase ◽

Emission Electron ◽

Triple Points

ABSTRACTThe grain boundary phase of silicon nitride containing additives Y2O3 and Nd2O3 has been studied by means of a newly developed 300kV field emission ATEM. The composition of the two-grain boundary phase of about 1 nm thick is successfully determined. It is then found that the compositions among the grain boundaries are not the same and the additives of Y2O3-Nd2O3 are poor in the two-grain boundary, while they are rich in the triple points.

Download Full-text