An etching (85%H3PO4, 120C; 37%HCl, 100C) study was made of the (00•1) planes of flux-grown crystals. Fractography revealed a 1-to-1 correspondence of cleavage patterns on the 2 matched (00•1) cleaved planes. The etch patterns included: hexagonal point-bottomed pits with smooth sloping planes, hexagonal flat-bottomed pits, geometrically centered hexagonal pits with regularly spaced terracing, eccentric hexagonal pits with irregularly spaced terracing, large flat-bottomed hexagonal pits with smaller point-bottomed hexagonal pits within (having different geometrical centers) and flat-bottomed pits with a beak at their centers. It was concluded that these were associated with normal, inclined, stepped and bending dislocations.

U.Raina, S.Bhat, P.N.Kotru, F.Licci: Journal of Materials Science, 1996, 31[31], 3035-42