Lithium niobates applications

Barium titanate is one example of a ferroelectric material. Other oxides with the perovskite structure are also ferroelectric (e.g., lead titanate and lithium niobate). One important set of such compounds, used in many transducer applications, is the mixed oxides PZT (PbZri-Ji/Ds). These, like barium titanate, have small ions in Oe cages which are easily displaced. Other ferroelectric solids include hydrogen-bonded solids, such as KH2PO4 and Rochelle salt (NaKC4H406.4H20), salts with anions which possess dipole moments, such as NaNOz, and copolymers of poly vinylidene fluoride. It has even been proposed that ferroelectric mechanisms are involved in some biological processes such as brain memory and voltagedependent ion channels concerned with impulse conduction in nerve and muscle cells. 

Earlier work on photorefractive materials was centered on the discovery of the properties of the phenomenon in optical crystals, most notably lithium niobate, strontium barium niobate, and barium tantalate. Both the mathematics of the theory of photorefraction outlined above and its application to these materials and... 

In contrast, the nonlinearities in bulk materials are due to the response of electrons not associated with individual sites, as it occurs in metals or semiconductors. In these materials, the nonlinear response is caused by effects of band structure or other mechanisms that are determined by the electronic response of the bulk medium. The first nonlinear materials that were applied successfully in the fabrication of passive and active photonic devices were in fact ferroelectric inorganic crystals, such as the potassium dihydrogen phosphate (KDP) crystal or the lithium niobate (LiNbO,) [20-22]. In the present, potassium dihydrogen phosphate crystal is broadly used as a laser frequency doubler, while the lithium niobate is the main material for optical electrooptic modulators that operate in the near-infrared spectral range. Another ferroelectric inorganic crystal, barium titanate (BaTiOj), is currently used in phase-conjugation applications [23]. 

The thiocyanate method (in various modifications) has been used in determinations of molybdenum in plant material [158], natural waters [28,41], cast iron and steel [25,56,159,160], tantalum, niobium, and tungsten [2], vanadium and its compounds [27] corundum and lithium niobate [55], ores and minerals [161,162], uranium concentrates [29,163] lithium fluoride [164], platinum chloride [42], and fertilisers [56]. A review of applications of the thiocyanate method for determining Mo has been given [165]. 

Lithium Niobate Lithium niobate (LiNbOj) is widely used as a photonic material, and has a wide range of applications in lasers, nonlinear optics, optical communications, optical memories, and diffractive optics [25O[. It is not generally considered as an ionic conductor. However, since Li NMR measurements first revealed a rapid Li ion motion in nanocrystalline powders prepared by ball-milling [251], the material has attracted considerable interest and has proved to be a good model system [ 169]. As stated earlier, it is now known that the ball-milled material has a considerable amorphous content, as shown by EXAFS [169,252] and HRTEM [169],... 

Since the early days of ferroelectric low molar mass LC research, the exploration of the NLO properties of these substances has been a topic of interest. For a recent review on SHG in ferroelectric LCs, see [215]. Unfortunately, the SHG efficiency of most ferroelectric LCs investigated so far [216-219] is orders of magnitude below that of state-of-the-art inorganic crystals, such as lithium niobate. The main reason for the low electronic NLO activity is that the ferroelectric LC compounds and mixtures used in these investigations were optimized for display applications rather than for NLO performance. Quite recently, some research groups started the development of ferroelectric LC compounds specifically devoted to NLO applications, and indeed improved the SHG efficiency by orders of magnitude [220-224]. 

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