Showing papers on "Lanthanum published in 1985"

Enhancement of humidity sensitivity for Perovskite-type oxides having semiconductivity.

Abstract: The humidity sensitivities of SrSnO3 and BaSnO3 were enhanced slightly By means of calcining their hydroxides, which were prepared by a coprecipitation method. The partial substitution of the A site element of the perovskite-type oxides with lanthanum was more useful for the enhancement of the sensitivity. The highest sensitivity was found in Sr0.95La0.05SnO3 among the specimens studied.

Effect of R3+ Ions on the Structure and Properties of Lanthanum Borate Glasses

Abstract: The present investigation of glass formation in the (mole percent) systems 25La2O3 (x)R2O3 (75-x)B2O3, where R = Al, Ga, and (25-x)La2O3 (x)Ln2O3 75B2O3, where Ln = Gd, Er, Y, notes that up to 25 mol pct Al2O3 or Ga2O3 can be substituted for B2O3, while no more than about 5 mol pct Ln2O3, substituted for La2O3, caused macro-phase separation. The substitution of either R2O3 or Ln2O3 in the lanthanum borate system changes the separation distance between adjacent B3O6 chains. The effect of this structural change on the molar volume, transformation temperature, thermal expansion coefficient, and transformation-range viscosity is discussed.

Preparation of γ‐LaSy (1.33<y<1.50) alloys by the pressure‐assisted reaction sintering method and their thermoelectric properties

Abstract: The pressure‐assisted reaction sintering (PARS) method was used to prepare thermoelectric elements of the γ‐phase lanthanum sesquisulfide solid solution alloys which exist over a wide homogeneity range: LaSy (1.33

Electrostriction in Lead Lanthanum Zirconate-Titanate Ceramics

Abstract: Electric polarizations and elastic strain were measured simultaneously for several lead lanthanum zirconate-titanate (PLZT) compositions cycled around their high-field electric hysteresis loops. Using the accepted symbolism for compositions, where the first number gives the mole percent of La2O3 and the second two numbers give the ratio of PbZrO3 to PbTiO3 in the composition, data were taken for (7,7.5,8,8.8,9.5)/65/35 and 8/70/30 compositions. The results show that for all compositions in which the base state is macroscopically nonpolar, the strains are dominantly electro-strictive in nature. Both of the polarization-related constants, Q11 and Q12, are almost independent of temperature and of the same order as in other perovskites but decrease slightly in magnitude with increasing La2O3 content.

Lanthanum fluoride coprecipitation technique for the preparation of actinides for alpha-particle spectrometry

Abstract: A simple and rapid procedure is described by which actinides can be mounted in a form suitable for alpha-particle spectrometry without recourse to electrodeposition. The actinides are coprecipitated as fluorides with 100 μg of lanthanum carrier from an acidic solution. The precipitate is mounted on a 0.1 μ-pore membrane filter containing LaF3 substrate, also prepared from 100 μg of lanthanum. The resolution obtained using samples of pure radiotracers and of frations isolated from lake sediments is generally comparable to that afforded by the conventional electrodeposition technique. The coprecipitation yield is generally quantitative. The entire procedure can be completed in about 90 min.

Gamma ray detector

Abstract: A gamma ray detector suitable for use in a positron CT and others is disclosed which comprises a scintillator formed of a single crystal of cerium activated gadolinium silicate which is expressed by a general formula Gd 2 (1-x-y) Ln 2x Ce 2y SiO 5 (where Ln indicates at least one element selected from a group consisting of yttrium and lanthanum, and x and y lie in ranges given by formulae 0≦x≦0.5 and 1×10 -3 ≦y≦0.1).

Determination of the hydrogen content in amorphous lanthanum-nickel (LaNi5) films using a quartz-crystal mass-monitoring method

Abstract: The hydrogen content in LaNi/sub 5/ films of various thicknesses was determined by a quartz-crystal mass-monitoring (QCMM) method. The hydrogen concentration increased with increasing film thickness. Pressure-composition isotherms of hydrogen in LaNi/sub 5/ film indicated that the hydrogen concentration increased with an increase in pressure and a pressure plateau was absent.

New Compound in the System La2O3-Al2O3

Abstract: A new compound, 5La2O3-2Al2O3, is formed from an amorphous material prepared by the simultaneous hydrolysis of lanthanum and aluminurn alkoxides. It has an orthorhombic unit cell with a=0.9704 nm, b=0.5967 nm, and c=1.5473 nm. The structure contains tetrahedral AlO4 groups and octahedral AlO6 groups.

X-ray photoelectron spectroscopy of a cerium-doped lanthanum aluminosilicate glass

Abstract: Core-level XPS spectra of a Ce-doped La aluminosilicate glass are reported. A deconvolution of the o 1s peak into two subpeaks corresponding to bridging and non-bridging oxygens indicates that 66% of the Al ions occupy tetrahedral sites and that the number of non-bridging oxygens in a (Si, Al)O44− tetrahedron is 1.20 which is consistent with the value obtained from the Si 2p chemical shift. The 3d core levels of Ce and La show main and satellite peaks. The broadening of the Ce and La peaks in the glass compared with the spectra of the corresponding sesquioxides is attributed to the random nature of the glassy host.

Solvent extraction of lanthanum(III) from sulphuric acid solutions by Primene JMT

Abstract: The distribution of lanthanum(III) between aqueous H2SO4 solutions and Primene JMT in the organic phase is described. The dependence of the extraction on acidity, extractant concentration and type of diluent was investigated. Aggregation numbers are calculated and a mechanism for the extraction is suggested. The separation of thorium(IV) from lanthanum(III), cerium(III) and cerium(IV) is outlined.

Complexes of carbohydrates with metal cations. XIV: Separation of sugars and alditols by means of their lanthanum complexes

Abstract: The mobilities of numerous polyols, sugars and methyl glycosides on ion-exchange resin thin-layer plates in the calcium and lanthanum form have been measured. Under these conditions, alditols which have a threo-threo sequence of hydroxy groups complex more strongly with lanthanum than with calcium, whereas methyl glycosides complex less strongly.

Process for preparing catalytic cracking catalysts

Abstract: Catalytic cracking catalysts and catalytic cracking process wherein the cracking catalysts are prepared by: (i) contacting a mixture of a large pore zeolite and an inorganic oxide matrix at effective conditions of temperature, pH and time with a fluoro salt; and (ii) ammonium exchanging the product of step (i) to provide a catalyst having less than 2.0 percent by weight Na2O, based on the weight of the zeolite. Optionally, the product is provided with an effective amount of at least one cation selected from the class consisting of serium, lanthanum, praseodymium, neodymium, promethium, samarium, europium, lutetium, gadolinium, terbium, dysprosium, holmium, erbium, thulium and ytterbium.

Reaction of yttrium with p-nitrochlorophosphonazo and the spectrophotometric determination of yttrium in nickel-base alloys in the presence of cerium sub-group rare earths

Abstract: Yttrium reacts with p-nitrochlorophosphonazo to form a 1 : 3 β-type complex, having an absorption maximum at 731 nm. The complex formation was complete within 10 min in a small volume of 0.2–0.5 M perchloric acid and the resulting complex was stable for at least 4 h after dilution. Under the conditions employed, the molar absorptivity was found to be 8.49 × 104 l mol–1 cm–1 at 731 nm. The determination range was 0–6 µg of yttrium in 25 ml of solution and was obtained using a standard addition-deduction method. Using this procedure yttrium can be determined in the presence of a 10-fold amount of lanthanum or cerium without separation. A selective and sensitive procedure for the determination of microamounts of yttrium in nickel alloys is described. The precision and recovery are both satisfactory.

Kinetics of cathodic oxygen reduction on lanthanum-based perovskite-type oxides.

Abstract: 15種のランタン系ペロブスカイト型複合酸化物を調製し,アルカリ水溶液中での酸素の電気化学的還元反応に対する触媒作用を,おもに回転リングデイスク電極(RRPE)法を用いて系統的に調べた。ほとんどの酸化物では,カーボンに対すう酸化物の混合量を増すと電極性能は向上し,中間生成物である HO2- の生成量は減少した。酸素還元に対する反応電子数(n)については,カーボン単独の場合はO, 酸化物を 80wt% 混合した場合には 2.3～4.0 となった。また H2O2 の分解速度の測定から,102.0, 種の酸化物に比較的高い分解能があることを見いだした℃ 以上の結果から,これらの酸化物は酸素の四電子還元と,HO2- の分解の両反応に対して触媒活性を有していることがわかった。したがって,これらの酸化物上での酸素還元にはつぎの二つの経路が考えられる。各反応に対する速度論的パラメーターを RRDE 法からのデータの解析によって求め,各酸化物を三つのグループに分類した。すなわち, LaCrO3 と LaFeO3 のような反応(i)および(iii)に対する活性が両方とも低いグループI, LaMnO3 などの反応(i)に対する活性だけが高いグループII,さらに両活性ともかなり高い LaNiO3 などの多くの酸化物が属するグループIIIである。電極触媒として優れているのはグループII とグループIII の酸化物であるが,それらめ中でも La0.6Sr0.4MnO3 (グループ)と La0.6 Sr0.4 Fe0.6 Co0.4O3 (グループIII)がとくに高い電極活性を示した。

Metal-nucleotide interactions. 3. Oxygen-17, phosphorus-31, and proton NMR studies on the interaction of scandium(III), lanthanum(III), and lutetium(III) with adenosine 5'-triphosphate

Abstract: Formation de complexes 1:2 M:ATP pour les 3 ions. Mesure des vitesses d'echange entre HTP libre et tri

Dielectric ceramic material

Abstract: Disclosed is a dielectric ceramic material comprising lanthanum magnesiumtitanate having a perovskite structure. The lanthanum magnesiumtitanate is preferably used in the form of a composition of the lanthanum magnesiumtitanate and calcium titanate as the dielectric ceramic material. The dielectric ceramic material has a small dielectric loss and a large dielectric constant, and the temperature coefficient of the resonance frequency can be controlled to a small value within a certain range. This dielectric material is valuable as a microwave resonator.

Ceramic temperature sensor

Abstract: A device for monitoring temperature as a function of electrical resistivity comprises a sensing element formed of a ceramic including lanthanum chromite with a dopant selected from magnesium oxide, aluminum oxide, titanium oxide, tin oxide and silicon oxide, and having electrodes operably affixed to the surface thereof.

Suppression of ferromagnetic order in pseudobinary U1−xLaxTe compounds

Abstract: We report first magnetic, electrical, and optical measurements on UTe diluted with lanthanum. With the substitution of 10% and 20% U by La, a decrease of TC by ≊30 and ≊60 K, respectively, is observed. From an extrapolation of these data a vanishing of ferromagnetic ordering is predicted to occur in U1−xLaxTe for x≊0.25. The electrical resistivity of all compounds shows a −log T term at higher temperatures and a maximum which shifts from 140 K for x=0–90 K for x=0.2. It is concluded that the dilution with nonmagnetic lanthanum weakens the interatomic exchange between uranium atoms and that the Kondo effect suppresses magnetic ordering.

Correlation between the stability of carbonates in ternary Ln2O3-H2O-CO2 hydrothermal systems and lanthanide systematics

Abstract: Phase diagrams for ternary Ln2O3-H2O-CO2 systems for the entire lanthanide series (except promethium) were studied at temperatures in the range 100–950 °C and pressures up to 3000 bar. The phase diagrams obtained for the heavier lanthanides are far more complex, with the appearance of a number of stable carbonate phases. New carbonates isolated from lanthanide systems (Ln ≡ Tm, Yb, Lu) include Ln6(OH)4(CO3)7, Ln4(OH)6-(CO3)3, Ln2O(OH)2CO3, Ln6O2(OH)8(CO3)3 and Ln12O7(OH)10(CO3)6. Stable carbonate phases common to all the lighter lanthanides are hexagonal LnOHCO3 and hexagonal Ln2O2CO3. Ln2(CO3)3• 3H2O is stable from samarium onwards and orthorhombic LnOHCO3 is stable from gadolinium onwards. On the basis of the appearance of stable carbonates, four different groups of lanthanides were established: lanthanum to neodymium, promethium to europium, terbium to erbium and thulium to lutetium. Gadolinium is the connecting element between groups II and III. This is in accordance with the tetrad classification for f transition elements.

Axial face seal (sliding ring seal)

Abstract: The present invention relates to an axial face seal (10) in which a seal element (1) comprises a sintered ceramic material containing aluminium oxide (alumina) and the seal element (1) is in contact with a counter-element (2) preferably made of carbon bonded with synthetic resin. The material of the seal element comprises from 60 to 93% by volume of aluminium titanate and the remainder is composed of up to: 20% by volume of aluminium oxide 25% by volume of titanium oxide 6% by volume of silicon oxide (silica) 5% by volume of iron oxide 10% by volume of zirconium oxide (zirconia) 10% by volume of magnesium oxide (magnesia) 5% by volume of one or more oxides of yttrium, lanthanum and cerium a maximum of 2% by volume of oxidic impurities and up to 20% by volume of reaction products of these oxidic compounds. All proportions by volume, with the exception of the proportion of pores, add up to 100% by volume.

X-ray analysis of Lymnaea stagnalis muscle fibres does not suggest that the sarcolemma is permeable to lanthanum ions.

Abstract: The cross-striated muscle from the heart ventricle and the smooth penis retractor muscle of the freshwater snail Lymnaea stagnalis have been investigated by X-ray microanalysis to establish whether lanthanum can cross the plasma membrane, as has been reported by other investigators. Tissues were incubated in 1 mM ionic lanthanum before fixation in phosphate- or cacodylate-buffered fixative. X-ray mapping for emissions in the lanthanum energy range indicates a concentration of emissions that coincided only with the network of sub-surface transverse tubules formed by the invagination of the plasma membrane and with the plasma membrane/extracellular space interface. X-ray energy spectra were collected from various cell compartments; peak-to-background ratios were obtained and analysed statistically. Cacodylate buffer is less effective than phosphate buffer in precipitating lanthanum, but no evidence to suggest the redistribution of lanthanum in cacodylate-buffered preparations was found. Lanthanum is precipitated only in the sub-surface transverse tubules and at the plasma membrane/extracellular space interface in both heart ventricle muscle and penis retractor muscle, fixed in either phosphate or cacodylate buffer. There was no evidence of lanthanum precipitation in the background cytoplasm or on any cytoplasmic organelle. These results confirm our hypothesis that lanthanum does not cross the plasma membranes in these molluscan tissues.

Catalytic cracking catalysts for high octane gasoline products

Abstract: Catalytic cracking catalysts, the process of their preparation and the process of their use. Cracking catalysts are disclosed for improving the octane number of gasoline products. The catalysts comprise a zeolitic aluminosilicate having a mole ratio of oxides in the dehydrated state of (0.85-1.1) M2/nO : Al2O3 : xSiO2 wherein M is a cation having a valence of "n" and "x" has a value greater than 6.0 to about 11.0; has an x-ray powder diffraction pattern having at least the d-spacings of Table A; has extraneous silicon atoms in the crystal lattice in the form of framework SiO4 tetrahedra; has between greater than zero to less than 5.0 percent by weight, expressed as the oxide, of at least one rare earth cation selected from the group consisting of cerium, lanthanum, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium; and less than 1.2 weight percent Na2O based on the weight of the aluminosilicate.

Effect of chloride incorporation on the crystallization of zirconium-barium-lanthanum-aluminum fluoride glass

Abstract: One aspect of the influence of preparation procedure on the crystallization behavior of a zirconium-barium-lanthanum-aluminum fluoride glass was studied. The crystallization pattern of this glass may be affected by the chlorine concentration within it. In particular, when such glasses are heated at low temperatures, the alpha-Ba-Zr-F6 crystalline phase forms only in those glasses which contain chloride.