Observations of Dislocations in Ammonium Dihydrogen Phosphate: Production of Dislocation-Free Crystals

Deslattes, Richard D.; Torgesen, John L.; Paretzkin, Boris; Horton, Avery T.

doi:10.1063/1.1708211

Cited by 33 publications

(3 citation statements)

References 12 publications

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“…Diffraction of X-rays in Bragg and Laue geometries by flat perfect crystals is well understood (Zachariasen, 1945;James, 1963;Hirsch & Ramachandran, 1950;Cole & Stemple, 1962;Batterman & Cole, 1964) and has been studied and tested in crystals where these assumptions hold to a good first approximation (K/illne & Aberg, 1975;Bearden, Marzolf & Thomsen, 1968;Deslattes, Torgeson, Paretzkin & Horton, 1966).…”

Section: Introductionmentioning

confidence: 99%

X-ray diffraction of bent crystals in Bragg geometry. I. Perfect-crystal modelling

Chantler¹

1992

J Appl Cryst

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X-ray reflectivity, widths, centroid shifts and profiles for curved perfect crystals are calculated from a model. The crystal is approximated by a stack of perfectcrystal lamellae or blocks with a gradually changing (mean) orientation. A computer program has been developed to calculate the above quantities in the Johann geometry for the composite crystal from the dynamic theory of diffraction. Focusing and defocusing aberrations and the use of photographic detection methods are included. Correction of omissions from earlier theory and modelling is noted, together with observed effects. Incoherent scattering can give dramatic changes in diffracted intensities and significant shifts of final parameters. Effects of depth penetration on shifts, cosine ratios and other parameters are included. Assumptions of the model and implementation are detailed. It is shown that interference effects between waves of roughly equal amplitudes require use of lamellar thicknesses greater than those corresponding to the Darwin range. Internal tests demonstrate agreement with the literature at extremes. The theory is applied to first-and fourth-order spectra in differential Lyman ~ wavelength measurements. Resuits for pentaerythritol 002 crystals are presented. Paper II of this series extends this model to nonideally imperfect crystals and other crystals of interest and discusses experimental agreement.

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Section: Introductionmentioning

confidence: 99%

X-ray diffraction of bent crystals in Bragg geometry. I. Perfect-crystal modelling

Chantler¹

1992

J Appl Cryst

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“…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.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2019

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A new type of X‐ray facility, the Beam Expander Testing X‐ray facility (BEaTriX), has been designed and is now under construction at INAF–Osservatorio Astronomico di Brera (Merate, Italy) to perform the acceptance tests of the silicon pore optics modules of the ATHENA X‐ray telescope. Crystals of high perfection and large dimensions are needed in order to obtain a wide beam (20 × 6 cm) with an X‐ray divergence of <0.5′′ and an X‐ray energy purity ΔE/E < 10−5. To generate X‐ray diffracted beams at an X‐ray energy of 1.49 keV, ammonium dihydrogen phosphate (ADP) crystals have been considered among other possible choices, because of their reported crystal quality and because they can be grown at sufficiently large size at a reasonable price. In the present paper, the results of the characterization of crystalline quality and lattice planarity of a 20 × 20 × 2 mm ADP sample are reported.

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“…Surprisingly little work has been carried out in this area, although the isomorphous solid, potassium dihydrogen orthophosphate has been well examined. In the few studies which have been made, X-ray topographic techniques have been used to define the propagation of dislocations during growth kinetic examinations (Chernov, Smol'skii, Parvov, Kuznetzov & Rozhanski, 1979) or to assess the quality of the grown crystals (Yoshimatsu, 1966;Deslattes, Torgesen, Paretzkin & Horton, 1966;Lefaucheux, Robert & Manghi, 1982), rather than to define the defect structure. In an attempt to rectify this situation and to resolve the question of growth on the pyramidal faces, we have attempted a comprehensive examination of the dislocation structure of ADP crystals prepared in a variety of manners, the mechan-ical properties of the solid and the influence of growth and mechanically induced dislocations and impurities on growth kinetics.…”

Section: Introductionmentioning

confidence: 99%

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

Bhat¹,

Sherwood²

1983

J Appl Cryst

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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.

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Observations of Dislocations in Ammonium Dihydrogen Phosphate: Production of Dislocation-Free Crystals

Cited by 33 publications

References 12 publications

X-ray diffraction of bent crystals in Bragg geometry. I. Perfect-crystal modelling

X-ray diffraction of bent crystals in Bragg geometry. I. Perfect-crystal modelling

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

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

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