IMPERFECT LOW-ANGLE BOUNDARIES AND FRACTURE IN HYDROTHERMALLY GROWN BERLINITE CRYSTALS

We present evidence for finite and/or imperfect low-angle grain bounda ries and associated long-range stress fields, formed during the hydrot hermal growth of berlinite (alpha-AlPO4) crystals on multiple-seed-pla te arrays. These defective boundaries originate at angularly misaligne d junctions between adjacent seed plates as a result of the failure of some component sets of dislocations to propagate epitaxially into the new growth. Lacking a full complement of dislocations, the newly grow n boundary may be imperfect and generate long-range stresses, leading to fracture and/or plastic flow. (C) 1998 Elsevier Science B.V. All ri ghts reserved.