The growth and perfection of crystals of ammonium dihydrogen orthophosphate, NH4H2PO4. I. Dislocation characterization in self-nucleated crystals

Abstract

A combined theoretical analysis and experimental study has been made of the nature of dislocations which propagate in the prismatic and pyramidal growth sectors of ammonium dihydrogen phosphate (ADP). In general the line energies of the dislocations formed in both the sectors are less than 45 eV nm-~. A few higher-energy dislocations (123 eV nm-1) were characterized in the prismatic sectors. The line directions of dislocations which are formed in the pyramidal sectors are such that they propagate towards the growth-sector boundaries and cross into the prismatic sectors. Alternatively, they follow the growth-sector boundaries and emerge at the intersection of adjacent faces. Few, if any, dislocations propagate within these sectors. Consequently, although dislocation-controlled mechanisms of growth may contribute to the growth of the { 101 } faces of ADP in the early stages of growth, other mechanisms will dominate at longer times. In contrast, the prismatic sectors are more imperfect, containing both screw and mixed dislocations. For these sectors spiral-growth mechanisms are more likely to dominate at all stages of growth.

Dislocations in energetic materials. 2. Characterization of the growth-induced dislocation structure of pentaerythritol tetranitrate (PETN)

“…In fact, the most commonly occurring dislocation type is that of highest line energy. Dislocations with large line energies have also recently been observed in single crystals of ammonium dihydrogen orthosphosphate (Bhat, Roberts & Sherwood, 1983). These observations suggest that the line energy of a given dislocation is not necessarily the controlling factor in determining whether or not the dislocation occurs.…”

Characterization of ammonium dihydrogen phosphate crystals for soft X-ray optics of the Beam Expander Testing X-ray facility (BEaTriX)

“…They were proposed more than 30 years ago for nonlinear optical applications [see for instance Moritani et al (1983)]. Their structural characterization, performed by X-ray topography, has confirmed that the crystals are characterized by high crystal perfection (Deslattes et al, 1966;Bhagavannarayana et al, 2006;Bhat et al, 1983), nearly dislocation free and free of inclusions.…”

The growth rate variation of the (100) faces of ADP crystals in the presence of manganese ions

“…In general, transition metals used as impurities incorporate predominantly into the prismatic sectors of ADP. The changes of strain and defect content caused by incorporation of impurities can be easily observed by x-ray transmission topography and correlated with growth rate since the defect structure of this sector is quite simple [12].…”