Lanthanum phosphate

The lanthanum phosphate phosphor is usually prepared by starting with a highly purified coprecipitated oxide of lanthanum, cerium, and terbium blended with a slight excess of the stoichiometric amount of diammonium acid phosphate. Unlike the case of the aluminate phosphor, firing is carried out in an only slightly reducing or a neutral atmosphere of nitrogen at a temperature 1000° C. Also this phosphor is typically made with the addition of a flux,... 

The GdAlgB O QiCe ", Tb " is synthesized by a soHd-state firing of the rare-earth coprecipitated oxide plus boric acid and MgCO at 900° C in a slightly reducing atmosphere. As in the case of the lanthanum phosphate phosphor, a flux is usually used. The synthesis of this phosphor is further comphcated, however, by the fact that it is a ternary system and secondary phases such as gadolinium borate form and must then react to give the final phosphor. 

Effects of pH and mixing temperature on the continuous predpitation of lanthanum phosphate... 

Fig. 1 shows the reactor setup used for continuous precipitation of lanthanum phosphate. A tube made of silicone rubber was used as a reactor. The inner diameter of the reactor tube... 

Fig. 6. TEM images of lanthanum phosphate 3.3. Particle growth mechanism particle. (0°C, pH = 1.7)...

By investigating the effects of pH, it was shown that H2P04 was the actual precursor of lanthanum phosphate precipitation. The particle yield was proportional to the H2P04 concentratian. The number density was proportional to the square of the H2p04 concentration. A maximum particle size was obtained at an optimum precursor concentiation as a result of the tradeoff of the nuclealion and growth. 

S. Kagaya, M. Saiki, Z. A. Malek, Y. Araki, and K. Hasegawa, Coprecipitation with Lanthanum Phosphate as a Technique for Separation and Preconcentration of Iron(III) and Lead, Fresenius J. Anal. Chem. 2001,... 

Recent research has explored a wide variety of filler-matrix combinations for ceramic composites. For example, scientists at the Japan Atomic Energy Research Institute have been studying a composite made of silicon carbide fibers embedded in a silicon carbide matrix for use in high-temperature applications, such as spacecraft components and nuclear fusion facilities. Other composites that have been tested include silicon nitride reinforcements embedded in silicon carbide matrix, carbon fibers in boron nitride matrix, silicon nitride in boron nitride, and silicon nitride in titanium nitride. Researchers are also testing other, less common filler and matrix materials in the development of new composites. These include titanium carbide (TiC), titanium boride (TiB2), chromium boride (CrB), zirconium oxide (Zr02), and lanthanum phosphate (LaP04). 

Figure 39 Illustration of a possible lanthanum phosphate-calcium aluminate glass structure for lower LaP04 content in calcium aluminate, derived from Raman and NMR data. For clarity, only a segment of the network is portrayed, with some oxygen atoms removed from the diagram. Taken from Ref. [168].

Lanthanum phosphate coatings were deposited onto NEXTEL 610 alumina fibers of up to 3 feet in length. The coatings are dense and... 

Fig. 4 Scanning electron micrograph of 300 - 400 nm thick Nextel alumina fibers coated with lanthanum phosphate. The lower figure is a 5x magnification of the inset in the upper figure.

A.T. Hunt, CCVD Processing of Lanthanum Phosphate and Beta-Alumina Fiber Coatings for Mullite Matrix Composites, Contract DM19561712, NSF SBIR Phase 1 Grant, 1996. 

Ordonez-Regil, E. et al., Sorption of uranium(VI) onto lanthanum phosphate surfaces. Langmuir, 18,1911, 2002. 

Bourcet and Fong (46) in their study of energy transfer between cerium and terbium in lanthanum phosphates performed an analysis of the dependence of the donor luminescence decay with temperature, and found that the diffusion in the cerium system plays an important role in the energy transfer process. 

The influence of the cesium hydrogenophosphate content was examined in the case of lanthanum phosphate. Figure 1 presents the selectivity observed at 330°C for a 80 % conversion. 

Lanthanum carbonate is a phosphate binder that inhibits gastrointestinal (Gl) absorption of phosphate by forming highly insoluble lanthanum phosphate complex with dietary phosphate released from food during digestion. It is indicated for reducing serum phosphate in patients with end-stage renal disease. 

Hydrolyses of l-halo-2,2,2-trifluoroethanes (HCFC 133a, 133h, 134) in 2,2,2-trifluoroethanol (TFE) were studied in the presence of modified lanthanum phosphates. Thermodynamic equilibritun could be achieved when the reactions were carried out in the vapour phase. The order of reactivity and selectivity of the various catalysts seemed to be governed by impregnation of the lanthanum phosphate with the desired alkaline earth salt. 

The presence of an alkaline on the surface of lanthanum phosphate is necessary for catalytic activity. As depicted in table 3, a cation effect was observed and there was a direct correlation between the cation size and the catalytic effect. 

In these experiments a large quantity of lanthanum phosphate was prepared and after drying, impregnated with cesium salts. 

The conversion followed the order Cl>Br>F and with cesium modified lanthanum phosphate gave in all cases, a selectivity greater than 90 %. 

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