Grain alignment

Circular polarization Changing grain alignment aligned grains acting like retarder... 

Martin, P. G., 1974. Interstellar polarization from a medium with changing grain alignment, Astrophys. J., 187, 461-472. 

A dilute suspension of electrically and optically anisotropic colloidal particles becomes birefringent when subjected to an electric field. In random orientation the suspension is optically isotropic but when the grains align with a uniform electric field the suspension becomes anisotropic in particular the effective refractive index of the ordered suspension parallel to the field direction differs from its refractive index... 

NiO grows on MgO with both grains aligned so that corresponding planes and directions in the two crystals are nearly parallel. The difference in lattice parameter (Aa) will be accommodated by a square array of misfit dislocations. 

Besides the cubic laser materials, there have also been reports on anisotropic ceramic materials, e.g., strontium fluorapatite S-FAP, with grains aligned by using a magnetic field prior to sintering, has demonstrated QCW laser emission at 1063.1 nm under 807.5 nm diode laser pumping, although efficiency is still relatively low [125, 126]. 

Fibrous Grain-Aligned Silicon Nitrides (Large Grains) 355... 

Figure 8.11 Schematic illustration of superplastic forging and superplastic sinter-forging techniques for fabricating fibrous-grain-aligned silicon nitrides.

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