It was found that a layer of the nematic liquid crystal p-N-(p-Methoxybenzylidene) amino n-butylbenzen, extended on a triglycine sulfate crystal, takes on an orientational pattern which delineates the polarized domain structures. This technique quickly delineates domain structures in great detail and can be used on a wide variety of ferroelectric crystals. It is even applicable to a uniaxial regular type in which a domain structure cannot be detected by ordinary optical methods. The new method and the ordinary carbon powder pattern technique were compared on a triglycine sulfate crystal.
High optical sensitivity is observed in 0.1 wt% Ce-doped strontium barium niobate (SBN) crystals in the absence of an external electric field. Only 5–10 mJ/cm2 of incident 0.488-μm radiation is required to produce 10% diffraction efficiency, while the energy to erase holograms from the 80% to its 1/e diffraction efficiency level is 30–40 mJ/cm2 at the same wavelength. Holograms stored in Ce-doped SBN persist at least one month (decay time constant) if kept in the dark at room temperature.
The distribution of dislocations in strontium barium niobate (SBN) crystals is examined by etching and by optical microscopy, and the sources of the dislocations are also investigated. The dislocations can be put into three categories according to the characteristics of distribution patterns. The dislocations concentrated in the central region of the crystal originate from the dislocations and the residual surface damages in the seed. The dislocations aligned radially in the outer region of the crystal are generated by the lattice mismatching or thermal stress at the groove bottoms in the shoulder part of the crystal. Finally, the dislocations distributed randomly in the outer region are generated at the positions where Pt or SBN were adsorbed on the surface of the crystal body. Methods for eliminating the dislocations are also described.
Neodymium pentaphosphate (NdP5Oz4) single crystals are grown from polyphosphoric acids by controlling polymerization rate of the acids as a main growth parameter, Solubility of NdP5OI4 in polyphosphoric acids as well as morphology and growth rate of NdP5014 crystals are empirically correlated with polymerization rate, expressed by mean-condensed rate in this study. Based on thedata for epitaxial growth rates along <100>, <010>, and <001> axes, it becomes clear that morphological change of spontaneously nucleated crystals occurs because each axis growth rate shows a different polymerization rate dependence. The influence of temperature gradient given to phosphoric acid is also investigated. As a result, the shape of spontaneously nucleated NdP5Oz4 crystals can be arbitrarily controlled with rather high reproducibility.
Metal fluxes such as Ga, In, and Sn are developed for liquid phase epitaxial growth of rare earth ultraphosphates in place of phosphoric acid flux. Solubility curves of
NdP5O14
for these fluxes are obtained. Using a tin flux,
false(normalNd,Yfalse)P5O14
layers having a few to twenty microns thickness are successfully grown both on the (100)‐oriented
NdP5O14
and (001)‐oriented
Gd0.33Y0.67P5O14
substrates. A preliminary growth mechanism is also reported.
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