P. Delavignette

Characterization of grain boundaries in the hexagonal system based on tables of coincidence site lattices (CSL's)

A method for the characterization of coincidence cells is proposed for hexagonal crystals. It is based on a simple formulation of the orientation relationships for coincidence site lattices. Therefore tables of coincidence orientation are established for different axial ratios with rational values of (c/a)2. Possible practical cases of coincidence are characterized by their comparison with these tables. This comparison is preferably performed using the description given by a rotation angle of 180°.

Dislocation movements and deformation twinning in zinc

Abstract Deformation twinning is a predominant deformation mode for many h.c.p. metals. In order to contribute to the understanding of the mechanism of this deformation, the (1012) [1011] deformation twin mode has been examined for the case of zinc. TEM observations indicate the possible existence of two families of intrinsic dislocations on the (1012) twin plane (named “twinning” and tilt dislocations), which glide occasionally on that plane. A dislocation-type mechanism is, therefore, proposed as a possibility for deformation twinning.

Group-theoretical consideration of the CSL symmetry

A theoretical analysis for the computation of the coincidence site lattice (CSL) symmetry is presented. It is shown that three types of symmetry elements can exist and each one can be found by properly using the CSLs rotation matrix of the smallest-angle description. Thus, from the existence of the subgroup H1, the order of which is directly connected with the number of the different orientations that the sublattice Λ11 can have, a low-symmetry H1 group implies more possibilities for the formation of the corresponding CSL. From the existence of the symmetry elements of the second type, the smallest-angle rotation matrix can be a symmetry element but only of the fourth or sixth order. From the third type of elements a connection between CSLs of different Σvalues can exist. Since the analytical form of this smallest-angle rotation matrix can be deduced for every crystallographic system, the procedure described here is of general use. Thus a new classification of the different CSLs is possible according to their symmetry group. This allows the study of the CSL model from the symmetry point of view.

Use of the CSL symmetrically equivalent descriptions tables in the DSC lattice base computation

A combination of analytical expressions and a knowledge of symmetry is employed for the displacement shift complete lattice (DSCL) base computation. The method is of general use and its application to cubic and hexagonal systems is given. Tables containing all the symmetrically equivalent descriptions of one and the same coincidence site lattice (CSL) as a function of one description are given for both cubic and hexagonal systems.

HIGH-SYMMETRY TRIPLE JUNCTIONS IN POLYCRYSTALLINE SILICON

Triple junctions in polycrystalline silicon for solar cell applications have been studied by TEM (transmission electron microscopy). The typical characteristic of these junctions is the existence of high-symmetry interfaces, i.e. twins of different order. Whenever the triple junction contains two such interfaces, the intersection axis is a CSL (coincidence site lattice) symmetry axis. In this case the mutual relation of the grain boundaries of the triple junctions is revealed by symmetry rules, since the boundaries are described by symmetry elements of the corresponding CSL which do not belong to the symmetry group of the parent lattice. Therefore, the different variant orientations of these CSL symmetry elements, implied by the symmetry of the lattice, are used for the study of triple junctions. A junction is geometrically characterized by the point-group-symmetry properties. The observations concern symmetrically different triple junctions of the same type of macroscopically stable grain boundaries and faceted and microfaceted interfaces. It is shown that in silicon the thermodynamically favored twins are combined by specific symmetry rules. The results are discussed in accordance with the possible growth mechanisms.

Rigid body translation in the (\(\bar 2\)11) twin boundary in silicon

AbstractThe rigid body translation accompanying a (

A ∑=27 coincidence grain boundary in a Cu-Ni alloy

\bar 2

Grain boundary analysis in TEM. IV. Coincidence and the associated defect structure in tungsten carbide

11) twin boundary in silicon has been studied by transmission electron microscopy. From a detailed analysis of theα-type fringe systems in the 111, 311 and 2