摘要:

A zone-axis critical voltage is reported in the [001] transmission electron diffraction pattern of the superconducting ceramic La1.8Sr0.2CuOy. Experimentally, this is found to occur at 95 kV; simplified theoretical calculations indicate that the critical voltage is so highly sensitive to the crystal potential that it changes by > 5 kV for a 2.5% variation in oxygen vacancy content. In principle, this technique can now be used to measure the oxygen stoichiometry to within ±2.5% from a ∼ 1 nm region in a well characterized single-phase region, and should also provide a sensitive measure of the La stoichiometry. Problems with the absolute quantification of the method are discussed, and it is concluded that the major application of this effect lies in comparative measurements of stoichiometry variations from sample to sample, and compositional inhomogeneities within a single sample.

ISSN:0950-0839    

DOI:10.1080/09500838808227790

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A new Monte Carlo method which permits the direct calculation of incoherent phase diagrams is presented. The method involves maintaining each lattice quite separately during the calculation and determining the phase boundaries by equating both the chemical potential and the pressure between phases. The results of several calculations are presented as examples. This new simulation procedure may be applied to any type of incoherent phase diagram without the complication of metastability.

ISSN:0950-0839    

DOI:10.1080/09500838808227791

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

In a Ni3Al alloy deformed at 650°C, evidence is provided for glide of KearWilsdorflocks on a {111} plane, accompanied by dragging of antiphase boundaries.

ISSN:0950-0839    

DOI:10.1080/09500838808227792

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

By means of detailed calculations with the Finnis-Sinclair potential and short-memory augmented rate theory we have investigated the isotope effect for vacancy diffusion in b.c.c. α-Fe. The experimental value is consistent with a model in which a double barrier bars the diffusion path.

ISSN:0950-0839    

DOI:10.1080/09500838808227793

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

In this Letter we report calculated values of the volume of formation of Schottky defects in ionic crystals using a three-body-force shell model which includes the effects of charge transfer arising from electron shell overlap. It is shown that the volume-derivative method suggested by Gillan (1981) can reproduce the experimental data reasonably well when a suitable interionic potential is used.

ISSN:0950-0839    

DOI:10.1080/09500838808227794

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

X-ray and electron diffraction patterns reveal significant differences between as-cast and as-quenched Al6CuLi3alloys. The broadening of the reflections and their displacements from the exact icosahedral positions are more pronounced in the as-cast alloy than in the as-quenched alloy which exhibits a ‘better’ icosahedral order. These results imply that the possible existence of the icosahedral phase as an equilibrium state is questionable.

ISSN:0950-0839    

DOI:10.1080/09500838808227795

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Elastic and plastic unloading effects are described for aligned diamond pyramid indentations imposed on a (001) MgO crystal surface. Substantial elastic recovery effects are explained in terms of the theoretical Hertzian behaviour for a ball indentation test. Limited reversal of the plastic deformation field occurs, involving dislocation processes which first produce an extensive amount of slip and cracking during the loading portion of the indentation cycle.

ISSN:0950-0839    

DOI:10.1080/09500838808227796

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The bulk and shear moduli of samarium phosphate glasses decrease under hydrostatic pressure: this acoustic-mode softening means that when compressed, these glasses become more compressible! The elastic behaviour also changes with temperature in an anomalous way. In contrast the structurally similar lanthanum phosphate glasses show normal elastic stiffness dependences upon temperature and pressure. Hence the source of the anomalous elastic behaviour of the samarium glasses is the samarium ion and is probably a volume-dependent valence state.

ISSN:0950-0839    

DOI:10.1080/09500838808227797

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

ISSN:0950-0839    

DOI:10.1080/09500838808227798

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor