Grain boundaries in NiO. I. Relative energies of 〈001〉 tilt boundaries

Abstract

The relative grain boundary energy of nickel oxide is determined by studying the thermal grooving of bicrystalline samples containing symmetric tilt boundaries. The variation of intergranular energy with angular misorientation is similar t o that observed for metals. The relative energy for high tilt angles 0 2 4 " ) is roughly constant and equal to 0.66. The observation of "structural" dislocations in the case of grain boundaries near a coincidence orientation relationship indicates the existence of small cusps on the energy curve.Die relative Korngrenzenenergie von Nickeloxid wird durch Untersuchung der thermischen Riefenbildung von bikristallinen Proben, die symmetrische Kippgrenzen enthalten, bestimmt. Die Anderung der intergranularen Energie mit der Winkelfehlordnung ist der fur Metalle beobachteten ahnlich. Die relative Energie fur hohe Kippwinkel 0 2 4 ' ) ist nahezu konstant und betragt 0,66. Die Beobachtung von ,,Struktur"-Versetzungen im Fall von Korngrenzen in der Nahe der Koinzidenzorientierungsbeziehung zeigt die Existenz kleiner Spriinge auf der Energiekurve.

Grain boundary energy anisotropy: a review

“…For example, two sources reporting the energies of [100] symmetric tilt grain boundaries in NiO both show that it varies smoothly, as reported for Cu and Al (see Fig. 8a) [55,56]. However, the relative energies for symmetric [110] tilt grain boundaries show more variation [57].…”

The distribution of internal interfaces in polycrystals

“…For example, tilt boundaries in gold show a preference for densely packed low index planes such as {100}, {111}, {112} and {110} [72,73]. For [100] tilt boundaries in -Fe, {110} planes are observed to be special so that asymmetric tilt boundaries with one crystal terminated by {110} are favored over symmetric configurations [74]. A tendency for certain high index boundary planes has also been cited.…”

“…It is interesting to note that at some special points, the bicrystals can have noncrystallographic point symmetries. For example, all bicrystals in the cubic system with [100] misorientation axes have at least 4/mmm point symmetry, but for the 45°rotation, k(n) has a point symmetry of 8/m, as illustrated in Fig. 7.…”

Computer simulation of 〈001〉 tilt grain boundaries in nickel oxide

“…The dashed line on the diagram is intended only to show the smooth variation of these cusp points with angle. D. M. Duffy and P. W. Taaker Experimentally, the grain-boundary energies of these structures have been studied by thermal grooving techniques (Dhalenne, Revcolevshi and Gervais 1979) ; this gives the ratio of grain boundary to surface energy. Direct comparison with experiments is not possible because of the uncertainty in the surface energy.…”

“…Nevertheless, rigid displacements of the two halves relative to each other are included and, indeed, are an essential part of tJhe relaxation. The minimization of the energy with respect to all the variables is achieved by using an efficient Fletcher-Powell variable-metric method (Fletcher andPowell 1963, Norgett andFletcher 1970). The size of the explicitly relaxed region was chosen as 3n planes either side of a (nlo) boundary.…”