Influence Of La3 Research Articles

Influence of La3+ ion in the yttria matrix in improving the microhardness of infrared transparent nano LaxY2-xO3 sintered via hybrid heating

In the present work, hybrid sintering technique which couples the resistive heating and microwave heating is employed to sinter infrared transparent La0.15Y1.85O3 to 99.2% of the theoretical density for the first time to the best of our knowledge. The presence of La3+ in the yttria matrix improves the hardness properties to a greater extent without affecting the transmittance properties, but there is a deterioration in the thermal properties of the sample. So we have limited our studies to La0.15Y1.85O3 which shows better optical, thermal, and hardness properties. The pellets fabricated from the ultra-fine nano powder with average particle size of ~12 nm synthesized by combustion technique and sintered at 1430 °C with an average grain size of 0.22 μm show ~80.1% transmittance in the UV–visible region and 81% in mid infrared region. For a comparative study of the optical, mechanical, and thermal properties, two other variants of sintering strategies namely conventional sintering and microwave sintering are also employed. A comprehensive analysis on the hardness reveals that the hardness of the pellets sintered via hybrid heating is 9.73 GPa and is superior to the pellets sintered using the other two techniques. The thermal conductivity of the sample is also analyzed in detail. The results clearly indicate that the La0.15Y1.85O3 ultra-fine nano powder synthesised by the single-step combustion method and sintered via microwave hybrid heating shows better transmittance properties without compromising the mechanical properties, and can be used very effectively for the fabrication of infrared transparent windows and domes.

Influence of La3+ ions on δ-Bi1−xLaxB3O6 powders structure and photo-induced optical properties of their polymer composites

Polycrystalline powder samples of orthorhombic δ-Bi1−xLaxB3O6 (where x=0.025–0.075), synthesized by means of polymeric precursor method, were incorporated into photopolymer polyvinyl alcohol matrix. The composites were fabricated by simultaneous DC-electric field alignment and UV solidification using a 337nm wavelength nitrogen laser. Optically stimulated EO effect in δ-Bi1−xLaxB3O6 was studied under the illumination of 20ns Nd:YAG bicolor laser beams at 1064nm and 532nm wavelengths. The main role of the La3+ ions content in δ-Bi1−xLaxB3O6 on the electrooptical efficiency is here clearly observed. The temperature dependence of the photoinduced EO is also investigated.

Influence of La3+ additions on the phase behaviour and antibacterial properties of ZrO2–SiO2 binary oxides

The present study reports the influence of lanthanum (La3+) content on the phase stability and antibacterial activity of ZrO2–SiO2 binary oxides. Four different concentrations of La3+ additions in ZrO2–SiO2 binary oxides were synthesized using a sol–gel technique. Heat treatment of the synthesized powders resulted in the formation of t-ZrO2 phase at 1000°C. Heat treatment beyond 1000°C resulted in the phase degradation of t-ZrO2 to yield m-ZrO2 and ZrSiO4. Results from antibacterial tests confirmed the potential activity of La3+ doped ZrO2–SiO2 binary oxides in countering the microbial invasion.

Effect of La3+ incorporation on the spectroscopic properties of Yb3+ -doped Y1−x La x Ca4 O(BO3 )3 (x = 0.09 and 0.25) crystals

Through the partial substitution of Y3+ ions with La3+ ions in the structural framework of YCa4O(BO3)3, the Yb3+-doped mixed oxyborate Y1−xLaxCa4O(BO3)3 (x = 0.09 and 0.25) crystals have been grown and characterized. The La3+ content (x = 0.25) in the crystal far exceeds the La3+ doping limit (x = 0.1) previously reported, whereas the crystal remains transparent and free from cracks. Optical absorption, emission and fluorescence decay measurements have been performed at room temperature, and the influence of La3+ doping on the spectroscopic characteristics of the crystals has been presented and discussed in detail. The main spectral and laser parameters pertinent to laser potential have been evaluated and compared with those of other oxyborates. The perspectives for application of the Yb3+:Y1−xLaxCa4O(BO3)3 crystals as laser media have been discussed.

Structural and Magnetic Properties of Different Temperature Sintering La-Substituted Barium Ferrite

The Ba1-xLaxFe12O19 (0.0≤x≤0.6) ferrite materials were prepared by the standard solid state reaction technique method and sintered at 920 °C with 4 wt% Bi2O3 and at 1150 °C without Bi2O3 in air. The influence of La3+ contents on the microstructure, density, and magnetic properties were studied. The XRD results showed essentially single phase spinel structure. The SEM images of the samples had no obvious relationship with the substituting value. Saturation magnetization continuously decreased from 59.37 emu/g to 57.93 emu/g with sintering temperature from 1150 °C to 920 °C. However, coercive force reached the value of 4547.0 Oe when x=0.6 at 920 °C. The density of the samples also decreased monotonously with increasing x value.

Influence of La3+ and Fe3+ co-doping to nano-TiO2 prepared by graded calcination

The un-doping, single-doping and co-doping TiO2 nanoparticles have been prepared through the graded calcination method with Ti(OC4H9)4 as raw material and characterized by X-ray diffraction (XRD) and UV–vis reflection spectra. Their photocatalytic activities have been investigated by the photocatalytic oxidation of methyl orange. It is indicated that Fe3+-doping makes the reflection profile narrow, improves photoutilization of TiO2, and then generates more electron–hole pairs. La3+-doping restrains the increase of grain size, leads to crystal expansion plus matrix distortion and retards the recombination of the photoexcited charge carriers. The photocatalytic activity of TiO2 co-doped with La3+ and Fe3+ is notably improved due to the cooperative actions of the two dopants.

Influence of temperature on the colloidal stability of the F-DPPC and DPPC liposomes induced by lanthanum ions

The influence of La3+ on the colloidal stability of liposomes made up by two zwitterionic phospholipids, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1-palmitoyl-2-[16-fluoropalmitoyl-phosphatidylcholine (F-DPPC), in aqueous media has been investigated by dynamic light scattering and electrophoretic mobility. The critical aggregation concentration (c.a.c.) of La3+ for F-DPPC and DPPC liposomes were experimentally obtained, and the results were compared with theoretical predictions using the Derjaguin–Landau–Verwey–Overbeek theory. In order to evaluate the influence of the state of the bilayer on the stability of liposomes, all experiments were performed at temperatures below and above the chain-melting phase-transition temperature of lipids (transition temperature of lipids). Changes in the size of both types of liposomes and high values of polydispersity in the presence of La3+ showed that these ions induce aggregation of liposomes at 25°C and at 60°C.At 25°C, when the bilayer of F-DPPC liposomes is interdigited, DPPC liposomes are more resistant to aggregation than the liposomes formed with F-DPPC. However, this difference disappears at 60°C, when both bilayers have the same conformation.The experimental results also indicate that the c.a.c. is higher at 60°C than at 25°C for both types of liposomes. In fact, it has been observed by dynamic light scattering measurements that aggregation of liposomes at 25°C can be prevented by increasing the solution temperature for La3+ concentrations near to the c.a.c. Moreover, the behavior of these liposomes in the presence of the ion was studied at temperatures above and below the transition temperature of the phospholipids.

Microwave Dielectric Properties Trends in a Solid Solution (Bi1−xLnx)2Mo2O9 (Ln=La, Nd, 0.0≤x≤0.2) System

The influence of La3+ and Nd3+ substitution for the Bi3+ cations in the low‐firing Bi2Mo2O9 system is considered in regard to the sintering behavior, density, phase composition, and microwave dielectric properties. All the compositions can be sintered to high densities in temperature range of 620°–680°C. In (Bi1−xLnx)2Mo2O9 (Ln=La, Nd) ceramics, when x≤0.2 the solid solution is within a monoclinic phase (P21/n) and the phase had an increase in melting temperature with the doping. In the La substitution case, the (Bi0.8La0.2)2Mo2O9 ceramics had the best microwave dielectric properties with a permittivity of 32.7, a Qf value (f=resonant frequency, Q=1/dielectric loss at f) of 13 490 GHz and a temperature coefficient of −4.6 ppm/°C. With the Nd‐substituted samples, the (Bi0.9Nd0.1)2Mo2O9 ceramics had the best microwave dielectric properties with a permittivity of 33.9, a Qf value of 15 200 GHz and a temperature coefficient of +8.05 ppm/°C. The substitution of La and Nd can effectively modify the microwave dielectric properties of Bi2Mo2O9 ceramic and in particular adjust the temperature coefficient to near zero. The (Bi1−xLnx)2Mo2O9 (Ln=La, Nd) ceramics are very interesting new materials for an ultralow‐temperature cofired ceramics technology that is compatible with Al metal electrodes.

Influence of La<sup>3+</sup> Ions on the Photo-Catalytic Activity of TiO<sub>2</sub> Films Prepared by Micro-Plasma Oxidation Method

Micro-porous TiO2 ceramic films have been grown on titanium plates by the micro-plasma oxidation method with the electrolyte of H2SO4. The influence of La3+ ion addition in the electrolyte on the photo-catalytic activities was investigated. The results showed that titanium dioxide thin films produced with La3+ addition electrolyte exhibit higher photo-activity than pure electrolyte for the oxidation of rhodamine B. The removal of rhodamine B reaches 90% for 30 min when La3+ addition concentrate is 0.05 g/L. Experimental results of X-ray diffraction and atom force microscopy show that the increase in activity is related to change in the lattice parameters and cell volume.

Influence of La3+ ions on growth and NLO properties of KDP single crystals

Single crystals of pure and Lanthanum added KDP crystals were grown from aqueous solution. The influence of La3+ ions in KDP crystals is studied. Isolated centers are formed by La3+ ions in KDP structure along (100) plane. La3+ ions incorporated into superficial crystal growth layer and slightly affect the growth process as they generate weak lattice stresses. The creation of these weak lattice stress is confirmed by Vickers's micro hardness test. The HRXRD analysis showed reduced structural defects in the La added KDP in the (100) plane than pure KDP. The incorporation of La in the crystal was confirmed by EDAX analysis. The Kurtz's powder SHG efficiency was found to be 1.5 times that of pure KDP. The UV-Vis transmission spectra of La added KDP showed excellent transmittance from 1100 nm to 340 nm and did not show any change in lower cutoff wavelength with respect to pure KDP. Laser damage threshold value has been determined using Q-switched Nd:YAG laser operating at 1064 nm and with 65 ns pulses in single shot mode. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Influence of Lanthanum on the Accumulation of Trace Elements in Chloroplasts of Cucumber Seedling Leaves

Influence of La3+ on the accumulation of trace elements (75Se, 56 Co, 83 Rb, 48 V, 95 mTc, and 67Ga) in chloroplasts of cucumber seedling leaves was studied by a radioactive multi-tracer technique. At the same time, chloroplast contents of different concentrations of La3+ treatment were calculated. It was observed that chloroplast contents peaked at 0.02 mM La3+ treatment and that the uptake and distribution of these trace elements in chloroplasts of cucumber seedling leaves are different under different La3+ treatments. With the increase of lanthanum concentrations from 0.002 to 2 mM, the uptake percentages of 75Se, 56 Co, and 83 Rb presented an obvious increase and then sharply decreased in contrast to the non-lanthanum treatment, whereas there appeared a sharp decrease and then restored control level in the uptake of 48 V. The other two trace elements, namely 95 mTc and 67Ga, were accumulated only in the presence of 0.02 mM La3+. The results indicate that lanthanum treatments to growing the cucumber lead to the change of trace element uptake in the chloroplasts of leaves, which suggest that lanthanum might influence the accumulation of trace elements in chloroplasts of cucumber seedling leaves by regulation of various ion transport mechanisms, thus affecting the photosystem of leaves.

Determination of Fluid Inclusion Electrolytes by Atomic Absorption Spectroscopy as of the Water Leachates of Crushed or Decrepitated Quartz Samples from Madan, Bulgaria

Two methods of opening fluid inclusions in hydrothermal quartz from Madan (Bulgaria) – mechanical (crushing) and thermal (decrepitation), followed by water leaching of the released components – were applied and compared. Problems concerning the sample preparation procedure, such as choice of an optimal sample mass and grain fraction, contamination of the grain surfaces, as well as the influence of La3+ and Cs+ additions on the water leaches etc., are discussed. The mol ratios X/Na (X=K, Ca, Mg, Mn) were determined by flame or electrothermal vaporization AAS of the dilute solutions obtained. The total salinity of inclusion fluid estimated by classical microcryometry is used to calculate the total concentrations of the main ions (Na+, K+, Ca2+, Mg2+ and Mn2+) in the water phase of the inclusions. Furthermore, the maximum concentrations of Pb2+ and Cu2+ were evaluated.

Microcalorimetric Studies of the Toxic Action of La3+ on Halobacterium Halobium R1 Growth

AbstractA microcalorimetric technique was used to evaluate the influence of La3+ on Halobacterium halobium Rl growth. By means of LKB‐2277 bioactivity monitor, ampoule method at 37 °C, the thermogenic curves of Halobacterium halobium R1 growth were obtained. In order to analyze the results, the maximum power Pm and the growth rate constants k were determined, showing that values of Pm and k are linked to the concentration of La3+. Addition of low concentration of La3+ can cause a decrease of the maximum heat production and growth rate constant. However, high concentration of La3+ may promote growth of Halobacterium halobium R1, but at much higher concentration of La3+, the growth of Halobacterium halobium R1 is inhibited again. For comparison, the shapes of Halobacterium halobium R1 cell were observed by means of transmission electron microscope. According to the thermogenic curves and TEM photos of Halobacterium halobium R1 under different conditions, it is clear that metabolic mechanism of Halobacterium halobium R1 growth is changed with the addition of La3+.

Microcalorimetric investigation of the effect of La3+ on mitochondria isolated from avian chicken liver tissue cells

A microcalorimetric technique was used to evaluate the influence of La3+ on mitochondria isolated from the liver tissue of Avian chicken. By means of LKB-2277 bioactivity monitor, ampoule method at 37°C, we obtained the thermogenic curves of the metabolism of mitochondria. After isolation from the chicken liver tissue, mitochondria still have metabolic activity and can live for a long time depending on the stored nutrients. In order to analyze the results, the maximum power (P m) and the decline rate constants (k d) were obtained. The addition of La3+ results in an increase of the maximum heat production and decline rate constants. Furthermore, values of P m and k d are linked to the concentration of La3+. According to the thermogenic curves under different conditions, it is clear that metabolic mechanism of mitochondria has been changed with the addition of La3+.

An electrochemical and Raman spectroscopic study on involvement of La3+ ions in lactate dehydrogenase catalysis

The influence of La3+ on lactate dehydrogenase catalysis was investigated by electrochemical and FT-Raman techniques. The results showed that La3+ ions bind preferably with phosphate moiety and ribose group (3′-OH) connected to nicotinamide in coenzyme NAD+/NADH, destabilize the enzyme-coenzyme complex and inhibit LDH activity.

Inhibiting effects of lanthanum ion on calcite formation from CaCL2-NaHCO3 solutions at 25�C

The influence of La3+ on calcite formation was studied using CaCl2-NaHCO3 solutions. We adopted a closed system, where the pH change of the solutions was monitored in a closed vessel. The closed system reduces a number of thermodynamic variables of the solution, thus enabling us to calculate the amount of CaCO3 precipitate only from pH with the assumption of equilibria among dissolved components in solution. After the analytical inspection of the calculation and assumption on which the calculation is based on, it was applied to experiments of the calcite formation in a Teflon vessel. The mole concentration of lanthanum added in the experiments was smaller than 1/3000 of that of calcium ion in the solutions. The addition of lanthanum oxide, chloride, and nitrate caused the difference in the pH change of the solution. The decrease of pH was smaller when lanthanum reagents were added, indicating that the amount of CaCO3 precipitate decreased. The smallest decrease was observed when lanthanum chloride or nitrate salt was added. The X-ray diffraction study showed that the CaCO3 precipitated in any solutions were calcite. If an equilibrium is assumed, which is considered to be likely from the pH change, the ion activity product (IAP) calculated in this study increased about 6 times when lanthanum ion, whose concentration is only 1/14 000 mole of calcium ion, was present.

Analytical applications of furnace atomic non-thermal excitation spectrometry (FANES) and molecular non-thermal excitation spectrometry (MONES). Part. 5. Study of the MONES of PO and HPO for the determination of trace amounts of phosphorus

A method for the determination of phosphorus by the molecular non-thermal excitation spectrometry (MONES) of PO and HPO has been developed. The phosphorus was introduced into the furnace atomic non-thermal excitation spectrometry (FANES) source as a solution of sodium dihydrogen phosphate. The measurements were carried out at the bands that gave the maximum signals, for PO at 246.4 nm and for HPO at 507 nm. The electrical, thermal and chemical conditions were optimised and are discussed. In addition, the influence of La3+ as a chemical modifier on the MONES of PO and HPO was investigated. The best values for the detection limit were 700 pg of P (MONES of PO) and 3400 pg of P (MONES of HPO). By comparison with the best values obtained with commercial electrothermal atomisation atomic absorption spectrometry instruments, these values are better by factors of 8 and 1.6, respectively. However, the determination of P by FANES at 213.5/213.6 nm is the best method for investigations of phosphorus using the FANES source, in the presence of La3+ as a chemical modifier.

Comparison of the action of La3+ and Ca2+ on contraction threshold and other membrane parameters of frog skeletal muscle.

The influence of La3+ on contraction threshold, on membrane input resistance, and on action potential parameters was investigated in fibers of the sartorius muscle of the frog, and it was compared to that of Ca2+. The dependence of the contraction threshold on [La3+]0 in the presence of 0.5mM Ca3+ gave a sigmoid relationship between 0.1 and 5 mM La3+ with a shift of 23 to 34 mV to less negative potentials following a 10-fold increase of [La3+]0. The membrane input resistance was increased to various degrees in La-containing solutions, the increase being irreversible. The threshold of action potential generation was shifted to less negative potentials by 28 mV, and the duration at half-maximal amplitude was tripled by 0.5 mM La3+. In comparison a 10-fold increase of [Ca2+]0 in the range of 0.5 to 50 mM shifted the contraction threshold by 15 mV to less negative potentials. 17 mM Ca3+, a concentration having the same effect on contraction threshold as 0.5 mM La3+, increased membrane input resistance reversibly, shifted the action potential threshold by 16 mV to less negative potentials, and had only minor effects on action potential duration. Conduction was never blocked by Ca3+ as it was with 1 mM La3+. In the theoretical treatment, it is shown that the influence of Ca3+ on contraction threshold, but not that of La3+, may be accounted for by its screening and binding to negative surface charges according to the Gouy-Chapman theory of the diffuse double layer. To describe the action of La3+ on the contraction threshold an additional interaction of La3+ with neutral but amphoteric sites was considered.