Polygonal Platelets Research Articles

Oriented growth of BaCl2-phases in crystals of NaCl-1% BaCl2. I. Morphology

Abstract The morphology of BaCl2-crystallites (sizes ∼ 10-60 μm) in the form of rods and regular or semi-regular polygonal platelets having various shapes and formed within an NaCl-matrix, has been studied by optical microscopy and X-ray diffraction. The crystallites are variously of cubic/non-cubic phases. The orientational relationship established for the interface between the matrix and the broad faces of platelets of the cubic phase (fluorite structure) is as follows: These interfaces are coherent with the matrix. Microhardness measurements indicate that crystals containing rod-like crystallites are 50% harder than those containing platelets.

Oriented Impurity Precipitates in Single Crystals of Sodium Chloride‐Barium Chloride

Single crystals of sodium chloride pulled from melt containing 1% by weight of barium chloride have been observed to contain a second phase precipitating throughout the interior in the form of thin rods (10–25µ long) and well defined polygonal platelets (10–15µ in size). Two types of rods have been observed, one type oriented along and the other along directions. The platelets are variously in the form of hexagons, octagons, decagons, and rhombi. The hexagonal and octagonal platelets seem to lie on {111} planes. Precipitates disappear on quenching the crystals and reappear on aging the crystals under suitable conditions.