Optical lanthanum

Zhang JWW, Zou YYK, Chen QS, Zhang R, Li KRK, Jiang H et al (2006) Optical amplification in Nd " doped electro-optic lanthanum lead zrrconate titanate ceramics. Appl Phys Lett 89 061113... 

Rare-earth compounds containing lanthanum are extensively used in carbon lighting applications, especially by the motion picture industry for studio lighting and projection. This application consumes about 25 percent of the rare-earth compounds produced. La203 improves the alkali resistance of glass, and is used in making special optical glasses. Small amounts of lanthanum, as an additive, can be used to produce nodular cast iron. 

Relatively smaller amounts of very high purity A1F. are used ia ultra low loss optical fiber—duotide glass compositions, the most common of which is ZBLAN containing tirconium, barium, lanthanum, aluminum, and sodium (see Fiber optics). High purity A1F. is also used ia the manufacture of aluminum siUcate fiber and ia ceramics for electrical resistors (see Ceramics AS electrical materials Refractory fibers). 

Bina Selenides. Most biaary selenides are formed by beating selenium ia the presence of the element, reduction of selenites or selenates with carbon or hydrogen, and double decomposition of heavy-metal salts ia aqueous solution or suspension with a soluble selenide salt, eg, Na2Se or (NH 2S [66455-76-3]. Atmospheric oxygen oxidizes the selenides more rapidly than the corresponding sulfides and more slowly than the teUurides. Selenides of the alkah, alkaline-earth metals, and lanthanum elements are water soluble and readily hydrolyzed. Heavy-metal selenides are iasoluble ia water. Polyselenides form when selenium reacts with alkah metals dissolved ia hquid ammonia. Metal (M) hydrogen selenides of the M HSe type are known. Some heavy-metal selenides show important and useful electric, photoelectric, photo-optical, and semiconductor properties. Ferroselenium and nickel selenide are made by sintering a mixture of selenium and metal powder. 

PZT (lead zirconate titanate) and PLZT (lead lanthanum zirconate titanate) combine ferroelectic, optical, and electronic properties and are used in optoelectronic and piezoelectric devices. Powders for hot pressing produced by CVD are being investigated. 

This soft, silver white metal reacts with air and water. The oxide is applied in optical glasses with high refractive indices (special lenses for powerful cameras and telescopes). Used for special effects in optoelectronics and electronics. Lanthanum exhibits catalytic properties. It is a component of flint and battery electrodes. Lanthanum boride (LaB6) is the superior electron-emitter for electron microscopes. Lanthanum is the first of the series of 14 lanthanides, also called the "rare-earth" metals, whose inner N shells are filled with electrons. They do not belong on the "red list" of endangered species they are neither rare nor threatened with depletion. China is particularly rich in lanthanide ores. 

A variety of fiber optic thermometry systems using fluorescence sensors have been discussed or become available over the past years. Most of the earliest systems are based on the temperature-dependent fluorescence intensity of appropriate materials. One such example of an early commercial system is the Luxtron model 1000, shown in Figure 11.2, which utilized europium-activated lanthanum and gadolinium... 

The rare earth (RE) ions most commonly used for applications as phosphors, lasers, and amplifiers are the so-called lanthanide ions. Lanthanide ions are formed by ionization of a nnmber of atoms located in periodic table after lanthanum from the cerium atom (atomic number 58), which has an onter electronic configuration 5s 5p 5d 4f 6s, to the ytterbium atom (atomic number 70), with an outer electronic configuration 5s 5p 4f " 6s. These atoms are nsnally incorporated in crystals as divalent or trivalent cations. In trivalent ions 5d, 6s, and some 4f electrons are removed and so (RE) + ions deal with transitions between electronic energy sublevels of the 4f" electroiuc configuration. Divalent lanthanide ions contain one more f electron (for instance, the Eu + ion has the same electronic configuration as the Gd + ion, the next element in the periodic table) but, at variance with trivalent ions, they tand use to show f d interconfigurational optical transitions. This aspect leads to quite different spectroscopic properties between divalent and trivalent ions, and so we will discuss them separately. 

Figure 2. Diffraction camera for single-molecule electron diffraction. A Lanthanum hexaboride electron source is used. The laser and associated optics is rotated after each data readout for a new molecular beam orientation. Organic molecules are picked up within liquid helium droplets to form a molecular beam traversing the electron beam.

Highly pure lanthanum oxide is used to make optical glass of high refractive index for camera lenses. It also is used to make glass fibers. The oxide also is used to improve thermal and electrical properties of barium and strontium titanates. Other applications are in glass polishes carbon arc electrodes fluorescent type phosphors and as a diluent for nuclear fuels. In such apph-cations, lanthinum oxide is usually combined with other rare earth oxides. 

In the application of lanthanum oxide in glass use is made of the high index of refraction and the lack of color of this oxide. So today optical glasses with up to 40 % lanthanum oxide are made vhich are corrosion resistant. 

New developments have been made in the photographic and optical field with the design of more sophisticated lenses. The lanthanum optical glasses with a high index of refraction and low dispersion have been an outgrowth of the post war period. 

The lanthanum glasses were not developed until after 1935 and much of the experimentation on improvement of chemical durability and crystallization characteristics was performed during the 1950 s. These glasses have played a big part in overall improvements in many optical systems such as the modern camera. 

Approximately ten years ago, it was first reported by Haertling and Land (jj that optical transparency was achieved in a ferroelectric ceramic material. This material was, in reality, not just one composition but consisted of a series of compositions in the lanthanum modified lead zirconate-lead titanate (PLZT) solid solution region. The multiplicity of compositions, each with different mechanical, electrical and electrooptic properties has led to a decade of study in defining the chemical and structural nature of these materials in understanding the phenomena underlying their optical and electrooptic properties and in evaluating the practicality of the large number of possible applications (2-12),... 

Optical Properties. The addition of lanthanum oxide to PZT has a rather remarkable effect on the optical transparency, especially when the amount of lanthanum exceeds seven atom percent. Thin polished plates characteristically transmit about 67% of the incident light. When broadband antireflection coatings are applied to the major surfaces, this transmission is increased to greater than 98%. Surface reflection losses are a function of the index of refraction (n = 2.5) of the PLZT. 

Shibasaki et al. have reported an asymmetric nitroaldol reaction catalyzed by chiral lanthanum alkoxide 18 to produce an optically active 2-hydroxy-1-nitroalkane with moderate-to-high enantiomeric excesses (Scheme 8B1.10) [27]. Apparently this novel catalyst acts as Lewis base. The proposed reaction mechanism is shown in Scheme 8B1.11, where the first step of the reaction is the ligand exchange between binaphthol and nitromethane. This reaction is probably the first successful example of the catalytic asymmetric reaction promoted by a Lew i s base metal catalyst. Future application of this methodology is quite promising. 

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