Quantitative determination of antiphase boundary profiles in long period superstructures. I : real space analysis

Jérôme Planès , Annick Loiseau , François Ducastelle

We present a method combining chemical lattice imaging, using high resolution electron microscopy, and statistical analysis of numerically processed micrographs for determining, at least semi-quantitatively, the modulation function in any long period antiphase boundary structure (LPS) with wide APB generating a chemical disorder in their neighborhood. It is shown that these structures can be quantitatively represented by a generic modulation function in the form of a smoothed square wave involving three characteristic lengths : the lattice spacing, a0, the mean APB spacing, M, and the width of the smoothing, z0, The topologic and thermodynamic properties of the different structures can be expressed using the ratios M/a0, which determines the period, commensurate or not, of the structure, z0/M, which defines the APB profile and z0/a0 which measures the pinning of the APB to the lattice. The method has been applied to compare the LPS observed in Cu-Pd and in Ti-Al. It is shown that in both cases the LPS have a similar APB profile. In Cu-Pd, both M/a0 and z0/a0 are large so that the structures are incommensurate and belong to a high temperature regime. On the other hand, with small M/a0 and z0/a0 the LPS in Ti-Al are commensurate with pinned APB, which is typical of an intermediate temperature regime.

Domaines: Articles anciens

Jérôme Planès, Annick Loiseau, François Ducastelle. Quantitative determination of antiphase boundary profiles in long period superstructures. I : real space analysis. Journal de Physique I, 1992, 2 (7), pp.1507-1527. ⟨10.1051/jp1:1992224⟩. ⟨jpa-00246636⟩