Single crystals and polycrystals

The crystal figures shown in Fig. 9.2 were selected from sketches that appeared in a series of books published between 1913 and 1923, and all represent forms of single or twinned crystals larger than a few millimeters. They are mostly gem-quality diamonds. Other than these forms, there are translucent or opaque 

The classification and naming by Dana [9], [lO] and Orlov [11] of diamond forms 

Dodecahedral bounded by curved faces II cubic bounded by flat faces or cuboid. 

Spinel twins, etc IV coated stone, clear core and milky coat 

Shortbort VIII bort, aggregate of idiomorphic crystals 

---

P.S. Follansbee and G.T. Gray III, The Response of Single Crystal and Polycrystal Nickel to Quasi-Static and Shock Deformation, in Advances in Plasticity 1989 (edited by A.S. Khan and M. Tokuda), Pergamon Press, Oxford, 1989, pp. 385-388. 

D. Goldberg, G. Sauthoff. Effect of ageing at 673 K on the compressive behaviour of <110> oriented ("soft") NiAl single crystals and polycrystals with and without Ti additions, Intermetallics 4 143 (1996)... 

Yield Stress The effect of hydrogen on the yield stress of iron and steels is unpredictable. For very pure iron single crystals and polycrystals the yield stress is frequently found to be decreased by hydrogen, but it may increase or stay the same, depending on the dislocation structure, crystal orientation and purity of the iron . Little information is available for steels. 

Crystal structure Single crystal and polycrystal, single crystal appearing as cubiccrystal structure, and lattice constant is 0.3559-0.3570 nm. 

Often, it is not possible to obtain single crystals that are large enough to be worked with in a convenient manner. In those cases, physical properties must be measured on poly crystalline samples. There is always discrepancy, or disagreement, between measured physical properties of single crystals and polycrystals due to microstructural effects. Hence, physical properties measured from polycrystalline samples are sometimes considered less reliable from a reproducibility standpoint. 

Compare and contrast ductile with brittle fracture processes/pattems in single crystals and polycrystals. 

Fig. 134. Longitudinal field decoupling at lOOmK measured in CePt2Sn2 single crystal and polycrystal. The LF data of the polycrystal prove the spin system to be static, while it remains clearly dynamic in the single-crystalline material. Adapted fiom Luke et al. (1997a).

Fig. 8.8 a Photographs of the 2.4, 3.6, and 4.8 at % NdiYAG ceramics after heat treatment for single crystallization, b Microstmcture of the 2.4 at.% Nd YAG ceramic sample at the interface between the single crystal and polycrystal. Reproduced with permission from [61]. Copyright 2007, Elsevier... 

Compression Behavior of Quasi-Single Crystals and Polycrystals... 

However, it is often very difficult to identify the individual sources for inelasticity (compare, e.g., the discussion of results for CeRujSij from single crystal and polycrystal data). 

Single crystal and polycrystals of wiistite have been studied by many researchers using variety of experimental technologies such as X-ray diffraction (XRD), Neutron diffraction, Electron diffraction, Mossbauer spectroscopy etc. It is found that besides the 4 1 defect clusters, there are also other types of defect clusters which are formed by way of common face, common side and common angle based on... 

Noncalssical crystallization has attracted much interest in recent years. In classical models, crystalline materials were classified into single crystal and polycrystal. A variety of recent reports have showed mesocrystals as the intermediate states between single crystal and polycrystal. The present report focuses on mesocrystals and their related architectures consisting of the unit crystals. A variety of mesocrystals and their related architectures were categorized by the ordered state of the unit crystals. These new superstructures have potentials for a variety of applications, such as electrode and catalyst materials. 

Mesocrystals can be regarded as the intermediate state between single crystals and polycrystals. In the present article, mesocrystal is defined as the oriented nanocrystals in the same crystallographic direction. Recently, a number of reports have shown a number of related structures to mesocrystals. In this section, five types of mesocrystals and their related structures are introduced. The classification is based on the degree of the ordering and the orientation of the unit crystals, even though the size and shape of the unit crystals are different. 

Fig. 18. Single crystal and polycrystal YbCu2Si2 spectra taken under identical conditions (CMA analyzer, ISOmeV resolution, data of C.G. Olson at SRC). Note the large reduction in polycrystal divalent intensity even though the (rivalent intensities are equal.

---