Lanthanum Concentration Research Articles

Evolution of ferroelectric and piezoelectric properties of BiFeO3 ceramics doped with lanthanum and zirconium

In this study, we performed cation substitutions at Bi-site (La3+) and Fe-site (Zr4+) to investigate their possible benefit for the ferroelectric properties of BiFeO3 ceramics. The cations with higher valence (Zr4+) ought to suppress the formation of structural defects during syntheses, such as oxygen vacancies and Fe2+. These defects are responsible for high leakage currents and low breakdown voltages characteristic of the pure BiFeO3. However, doping only with Zr did not improve the ferroelectric properties of bismuth ferrite. These samples were unable to persist electric fields above 30 kV/cm. On the other hand, the increase in lanthanum concentration resulted in improved ferroelectric and piezoelectric properties of the samples, sustaining electric fields above 100 kV/cm. Among the investigated samples, the highest remnant polarization of 24 μC/cm2 and piezoelectric coefficient (d33) of 34 pC/N reached Bi0.85La0.15FeO3 sample at 160 kV/cm. The share of non-ferroelectric contribution to the total polarization of this sample was the lowest (∼ 11 %). When it comes to the co-doped samples, the addition of Zr transformed the behavior from leaky ferroelectric to predominantly leaky dielectric. It indicated that doping with La significantly improved the ferroelectric properties of bismuth ferrite ceramics. In contrast, even a low Zr concentration of 1 mol% could outbalance the influence of much larger La concentrations (10 and 15 mol%).

Assessing the physiological responses and uptake patterns of lanthanum and yttrium in rice and Phytolacca americana L.

The effects of rare earth elements (REEs) on plant physiology and bioaccumulation characteristics vary significantly. As a result, considerable attention has been directed towards the effects and toxicity of REEs on plants. REEs migrate and transform in the environment and are absorbed by plant roots. However, different plants exhibit varying capacities to absorb REEs, leading to diverse impacts on their growth. In our study, we subjected seedlings of rice and Phytolacca americana L. to a gradient of lanthanum and yttrium (La + Y) concentrations to evaluate the physicochemical effects and uptake patterns of these elements. We meticulously measured variables such as biomass, root length, and elemental concentrations of La and Y, as well as macronutrients (P, Na, K, Mn, Fe, Mg, Ca) and micronutrients (Cu, Zn) to decode the physiological responses to varying levels of La + Y exposure. Based on the known dualistic nature of REEs interaction with plants, our results reveal that the threshold of REEs to different plants is different, and this conclusion can serve well for the formulation of rare earth pollution remediation strategies. Importantly, the accumulation of La and Y in P. americana L. roots was significantly greater than in rice roots, by an order of magnitude, reflecting the unique uptake capacities of hyperaccumulators. Additionally, this research found that nutrient dynamics and the absorption patterns of La and Y within the plants diverged, suggesting that La uptake in P. americana L. may occur via Ca2+ ion channels. These insights enhance our understanding of REE-plant interactions and have broader implications for agriculture and environmental health.

Physical properties of La3+ ion doped Ni[sbnd]Zn based spinel ferrite nanomaterials for technological applications

Spinel ferrite nanoparticles are extensively utilized in various everyday applications due to their exceptional capabilities. They are highly effective and efficient for various applications such as energy storage devices, microwave, electrode design, fuel cells, and recording media. Based on these applications, five samples of lanthanum doped nickel‑zinc spinel ferrite Ni0.5Zn0.5LaxFe2-xO4 nanoparticles were synthesized using the sol-gel auto-combustion technique. The lanthanum concentrations varied as x = 0.00, 0.05, 0.10, 0.15 and 0.20. X-ray diffraction (XRD) analysis revealed the formation of single phase cubic spinel structure of the prepared samples. The crystallite size was determined using the Scherrer formula and the values lies in the range of 9.22 to 20.09 nm. The chemical composition of the prepared samples was confirmed using Fourier transform infrared spectroscopy (FTIR) analysis. Transmission electron microscopy (TEM) confirmed the agglomeration and spherical shape morphology of the nanoparticles with an average particle size of 40 nm. Magnetic properties along with La3+ ion concentrations were investigated using the vibrating sample magnetometer (VSM). The dielectric properties of the prepared samples were carried out using impedance analyzer with an applied frequency ranging from 1 MHz to 3 GHz. Furthermore, the polarization mechanism in the applied frequency range was discussed with relaxation behavior at high frequency. The impact of La3+ concentrations on different parameters such as dielectric constant, impedance, electric modulus, tangent loss, and Ac conductivity were also investigated. The investigation of dielectric parameters. The relaxation mechanism at high frequency provided a significant impact of such type of materials to store energy due lake of hopping between the tetra and octahedral sites by addition of La3+ doping. The prepared samples exhibit excellent magnetic as well dielectric properties which makes suitable for microwave devices and soft magnetic applications.

Exploring the structural, morphological, optical, and dielectric properties, along with photocatalytic performance of La-doped SrFeO3 nanofibers

This research focuses on the enhancement of photocatalytic properties in La-doped SrFeO3 nanofibers which were successfully synthesized using the electrospinning technique, with lanthanum concentrations (x = 0.0, 0.1, 0.3, 0.5, and 0.7). The doping effect on the structural, morphological, optical and dielectric characteristics was studied using X-ray diffraction, Scanning Electron Microscopy, Fourier Transform Infrared spectroscopy, UV–Visible spectroscopy and LCR meter. Also, the influence of distance (from tip to collector) on the diameter of the nanofibers is discussed. X-ray diffraction (XRD) analysis and the Rietveld refinement process validated the successful development of ferrite structures. The band gap decreased from 2.70 to 2.60 eV as the doping concentration increased. The dielectric constant has maximum value of 195.1 × 103 for x = 0.7 concentration. The highest level of photocatalytic activity at about 82% was observed for x = 0.7 concentration. These nanofibers can be used for applications in sensors, microwave-absorbing devices, and photocatalysis.

Pyroelectric Thermal Energy Harvester Based on Sol‐Gel‐Derived PLZT Films

The present work focuses on studying the pyroelectric properties of chemical solution deposition‐grown Pb1−xLax(Zr0.4Ti0.6)O3 films on nickel substrate which are annealed at constant temperature of 650 °C with lanthanum concentrations ranging from x = 2–8% respectively. Structural studies reveal polycrystalline nature in all the PLZT films. The dielectric constant values rise from 497 to 1048 as La doping concentration rises from 2% to 6% at a constant frequency of 1 MHz, reaching a maximum value of 1048 for 6% La doping with little variation in dielectric loss between 0.03 and 0.05. As La doping level increases from 2% to 6%, the remnant (Pr) and saturation (Ps) polarization values increase from 12 to 47 μC cm−2 and 18 to 53 μC cm−2 respectively. The leakage current is found to be 2.68 × 10−8 A for 2%‐doped PZT film and it reduces to 2.94 × 10−10 A for PLZT (6% doping) film. The influence of lanthanum doping on the pyroelectric properties has been studied in detail. The value of pyroelectric coefficient (p) is varied from 240 × 10−3 to 980 × 10−3 Cm−2 K−1 and current responsivity is varied from 960 × 10−10 to 3920 × 10−10 mV−1 with the variation in lanthanum content from 2% to 6%, respectively. The promising pyroelectric results found in PLZT films encourage these films in energy applications field.

Associations between urinary rare Earth elements with renal function: Findings from a cross-sectional study in Guangxi, China

BackgroundWith increased applications of rare earth elements (REEs) across various industries, evaluating the relationship between REEs exposure and potential health effects has become a public concern. In vivo experiments have established that REEs impact renal function. However, relevant epidemiological evidence on this relationship remains scarce. The objective of this study is to examine the impact of exposure to REEs on renal function. MethodsIn this cross-sectional study, 1052 participants were recruited from Guangxi, China. We measured urinary concentrations of 12 REEs using an inductively coupled plasma-mass spectrometer (ICP-MS). Multiple linear regression models were developed to explore the relationship between a single REEs exposure and the estimated glomerular filtration rate (eGFR), a marker of renal function. Weighted quantile sum (WQS) regression and Bayesian kernel machine regression (BKMR) were used to examine the combined effects of REE co-exposure on eGFR. ResultsIn the multiple linear regression analysis, increasing the concentrations of lanthanum (La, β: 8.22, 95% CI: 5.67–10.77), cerium (Ce, β:6.61, 95% CI: 3.80–9.43), praseodymium (Pr, β: 8.46, 95% CI: 5.85–11.07), neodymium (Nd, β:8.75, 95% CI: 6.10–11.41), and dysprosium (Dy, β:7.38, 95% CI: 4.85–9.91) significantly increased the eGFR. In the WQS regression model, the WQS index was significantly associated with eGFR (β: 4.03, 95% CI: 2.46–5.60), with Pr having the strongest correlation with eGFR. Similar results were obtained in the BKMR model. Additionally, interactions between Pr and La, and Pr and Nd were observed. ConclusionsCo-exposure to REEs is positively associated with elevated eGFR. Pr is likely to have the most significant influence on increased eGFRs and this might be exacerbated when interacting with La and Nd. Mixed exposure to low doses of REEs had a protective effect on renal function, which can provide some evidence for the exposure threshold of REEs in the environment. Trial registrationThe study has been approved by the Guangxi Medical University Medical Ethics Committee (#20170206–1), and all participants provided written informed consent.

Lanthanum-modified tobermorite synthesized from fly ash for efficient phosphate removal.

Phosphate removal from water by lanthanum-modified tobermorite synthesized from fly ash (LTFA) with different lanthanum concentrations was studied. LTFA samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and Brunauer‒Emmett‒Teller specific surface area analysis. The results showed that the LTFA samples were mainly composed of mesoporous tobermorite-11Å, and LTFA1 with a lanthanum concentration of 0.15M had a high specific surface area (83.82 m2/g) and pore volume (0.6778 cm3/g). The phosphate adsorption capacities of LTFA samples were highest at pH 3 and gradually decreased with increasing pH. The phosphate adsorption kinetics data on LTFA samples were most accurately described by the Elovich model. The adsorption isotherms were in the strongest agreement with the Temkin model, and LTFA1 showed the highest phosphate adsorption capacity (282.51mg P/g), which was higher than that of most other lanthanum-modified adsorbents. LTFA1 presented highly selective adsorption of phosphate with other coexisting ions (HCO3-, Cl-, SO42-, and NO3-). In addition, phosphate was adsorbed onto LTFA samples by forming inner-sphere phosphate complexes and amorphous lanthanum phosphate. This study provides technical support for development of efficient fly ash-based phosphate adsorbents.

Anthropogenic Coal Ash as a Contaminant in an Underwater Search. II. Beyond Beryllium, Lanthanum, and Uranium

It has been shown that the Beryllium, Lanthanum and Uranium concentrations in the “BeLaU” spherules are in the expected ranges of coal ash. It is reported that the average elemental concentration of 12 microspherules can be found in the COALQUAL database in 98% (49/50) of the elements examined. The “BeLaU pattern” is found to be not unique, it can be reproduced using a coal ash standard (SRM1633a) and a chondritic normalization. The ratio of rare-earth elements in the “BeLaU” spherules and the SMR1633a sample is of order unity. Comparisons against SRM1633a return only two elements with abundances statistically significantly lower than the coal ash standard of reference (or fractions of order unity), agreeing in 96% (52/54) of the elements tested. No elements show higher abundance than 10× the reference standard. Terrestrial coal ash is curiously very similar to the collected spherules. Origin from a recent meteoritic event remains uncertain.

NMR investigation of multi-scale dynamics in ionic liquids containing Li+ and La3+: From vehicular to hopping transport mechanism

The dynamics in mixtures of ionic liquid and monoatomic cations has been studied at different time scales ranging from the nanosecond up to the second. The mixtures were composed of cholinium bis(trifluoromethanesulfonyl)imide ([Chol][TFSI]) and LiTFSI, with LiTFSI mole fraction, ▪, spanning from 0 to 0.5 (saturated solution), and [Chol][TFSI] and ▪ from 0 to 0.12. The translational self-diffusion coefficients of ▪, ▪ and ▪ have been measured, along with NMR their relaxation times at various magnetic fields, in order to decipher the intertwined dynamics between the ions, and to reveal how the local dynamics impact the long range translational diffusion. When the concentrations of lithium and lanthanum are increased in the liquid, the long range dynamics of all the ions drop. In the case of LiTFSI, the self-diffusion coefficient of lithium becomes higher than the one of TFSI at high concentration, revealing a change in lithium transport mechanisms. The NMR relaxation data confirm this change, showing a clearer transition at ▪. It is interpreted as a change from a vehicular transport mechanism of the lithium below ▪ to a hopping mechanism above. A similar crossover seems to occur in the lanthanum solutions. This phenomenon seems correlated to the departure of the hydroxyl group of the organic cation from the lithium solvation shell.

Unraveling the Complex Interactions: Machine Learning Approaches to Predict Bacterial Survival against ZnO and Lanthanum-Doped ZnO Nanoparticles.

The rise in antibiotic-resistant bacteria is a global health challenge. Due to their unique properties, metal oxide nanoparticles show promise in addressing this issue. However, optimizing these properties requires a deep understanding of complex interactions. This study incorporated data-driven machine learning to predict bacterial survival against lanthanum-doped ZnO nanoparticles. The effect of incorporation of lanthanum ions on ZnO was analyzed. Even with high lanthanum concentration, no significant variations in structural, morphological, and optical properties were observed. The antibacterial activity of La-doped ZnO nanoparticles against Gram-positive and Gram-negative bacteria was qualitatively and quantitatively evaluated. Nanoparticles induce 60%, 95%, and 55% bacterial death against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus, respectively. Algorithms such as Multilayer Perceptron, K-Nearest Neighbors, Gradient Boosting, and Extremely Random Trees were used to predict the bacterial survival percentage. Extremely Random Trees performed the best among these models with 95.08% accuracy. A feature relevance analysis extracted the most significant attributes to predict the bacterial survival percentage. Lanthanum content and particle size were irrelevant, despite what can be assumed. This approach offers a promising avenue for developing effective and tailored strategies to reduce the time and cost of developing antimicrobial nanoparticles.

Preparation and study of La-doped bismuth sodium potassium titanate -strontium titanate piezoelectric ceramics to enhance energy storage properties

This study involves the introduction of lanthanum oxide into bismuth sodium potassium titanate, alongside strontium titanate, denoted by the La2O3-doped BNKT-ST samples with varied x values ranging from 0.000 to 0.030 mol % prepared by conventional solid-state reaction technique. The research comprehensively investigates the impact of lanthanum incorporation on the phase evolution, dielectric properties, scanning electron microscopy with energy-dispersive X-ray spectroscopy (EDAX), ferroelectric behavior, piezoelectric response, and energy storage density of the Bi0.5(Na0.84K0.16)0.5TiO3-SrTiO3 (BNKT-BST) ceramics. Powder X-ray diffraction analysis reveals a tetragonal phase structure in all ceramics. Scanning Electron Microscopy (SEM) is employed for surface morphology analysis, indicating that higher concentrations of lanthanum result in reduced grain sizes. The ceramic material demonstrates remarkable P-E hysteresis loops, featuring a prominent peak at an electric field intensity of 3 kV/cm. The trends in residual polarization (Pr) and coercive field (Ec) show ascending, descending, and subsequent ascending patterns with increasing lanthanum concentration. Dielectric measurement was carried out for different composition at various temperatures. The maximum dielectric constant (εr) ∼ 4553 was observed at 348 °C. The sample was poled at a voltage of 3-5 kV. Notably, at a La doping level of 0.020 mol%, the doped samples exhibit favorable performance, as evidenced by the highest piezoelectric coefficient (d33) of 121 pC/N observed in the poled samples. The 0.97BNKT-0.030ST ceramics showcase exceptional energy storage capacity, marked by an elevated energy storage density (W) of 0.26 J/cm3 and a notable energy storage efficiency of 58 %. This study suggests the promising application potential of lanthanum-doped BNKT-ST ceramic capacitors, which are lead-free and exhibit high power density energy storage. Consequently, the BNKT-ST ceramic material emerges as a prospective candidate for further development in actuator and energy storage applications.

Longevity and efficacy of lanthanum-based P remediation under changing dissolved oxygen availability in a small eutrophic lake.

We set out to study the seasonal variations in porewater phosphorus and lanthanum concentrations in the dated sediment cores from a small eutrophic lake that has been treated with Phoslock, a lanthanum-modified bentonite (LMB) amendment. Three sites were sampled when the hypolimnion was either oxygenated or anoxic: (i) the lake's deepest point, (ii) a littoral site receiving inflows from the catchment, and (iii) a littoral site influenced by nearby septic tanks. Phosphate (PO43--P), lanthanum (La), iron (Fe), dissolved organic carbon (DOC) and sulfate (SO42-) were measured in porewater samples. An inverse diagenetic model was used to quantify fluxes of dissolved elements across the sediment-water interface as well as the net rate of their reactions along the porewater concentration gradients. Results show that porewater P and Fe underwent strong seasonal dynamics, while La did not. P fluxes, 20-fold higher at the deepest site than elsewhere in the basin, were influenced by anoxic conditions in the hypolimnion during summer and winter, suggesting that P mobility remained sensitive to redox fluctuations despite the addition of La. At the deepest site, fluxes of P across the sediment-water interface increased from 1 to 9 × 10-9 μmol cm-2 s-1 between spring and summer, while the rate of P production to the porewater also increased a hundredfold. These increases were concurrent with Fe mobilization. Finally, sediment dating shows that the fraction of P sequestered by La is buried under freshly deposited sediment at a rate of 2-3 mm per year. These results indicate that external P fluxes and erosion control remain crucial to maintain the longevity of the LMB treatment.

In situ fabrication of lanthanum-doped nickel oxide nanostructures using sol-gel for the degradation of rhodamine B.

Nanoscale science represents a thriving field of research for environmental applications within materials science. This study focuses on the fabrication of pure and La-doped nickel oxide (NiO) nanostructures with varying concentrations (1.0, 2.0, 3.0, and 4.0 wt%) of lanthanum using a facile sol-gel technique. This study explores the structural, morphological, chemical composition, and optical characteristics of the resulting pure and La-doped NiO nanostructures. Techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, UV-visible spectroscopy, and photoluminescence (PL) spectroscopy were used for material analysis. The observed trend in the energy band gap (Eg) values demonstrates a continuous decrease up to a La-doping concentration of 3 wt% in NiO. However, after this concentration (at 4.0 wt%), there is a noticeable increase in the energy band gap. At lower La-doping concentrations (up to 3 wt%), the incorporation of La ions into the NiO lattice may result in the formation of defects and oxygen vacancies. The presence of these imperfections may lead to new energy levels into the band gap, resulting in partial filling and a subsequent reduction in the band gap. Beyond a specific doping concentration (e.g., 3 wt%), excess La atoms may aggregate or cluster inside the NiO lattice. This agglomeration may cause structural distortions, strain, and disturbances in the crystal lattice, resulting in an increase in the band gap. The 3 wt% La-doped NiO sample demonstrated a notable 84% degradation efficiency of the synthesized nanomaterials coupled with its inherent stability, highlighting its dual attributes of effective pollutant removal and sustained performance. Furthermore, the cyclic stability of the optimized nanostructure is anticipated to be ∼77.42% after six cycles, suggesting promising future applications in photocatalysis.

Ln-HOF Nanofiber Organogels with Time-Resolved Luminescence for Programmable and Reliable Encryption.

Developing tunable luminescent materials for high throughput information storage is highly desired following the explosive growth of global data. Although considerable success has been achieved, achieving programmable information encryption remains challenging due to current signal crosstalk problems. Here, we developed long-lived room-temperature phosphorescent organogels enabled by lanthanum-coordinated hydrogen-bonded organic framework nanofibers for time-resolved information programming. Via modulating coassembled lanthanum concentration and Förster resonance energy transfer efficiency, the lifetimes are prolonged and facilely manipulated (20-644 ms), realizing encoding space enlargement and multichannel data outputs. The aggregated strong interfacial supramolecular bonding endows organogels with excellent mechanical toughness (36.16 MJ m-2) and self-healing properties (95.7%), synergistically achieving photostability (97.6% lifetime retention in 10000 fatigue cycles) via suppressing nonradiative decays. This work presents a lifetime-gated information programmable strategy via lanthanum-coordination regulation that promisingly breaks through limitations of current responsive luminescent materials, opening unprecedented avenues for high-level information encryption and protection.

A human health risk assessment of rare earth elements through daily diet consumption from Bayan Obo Mining Area, China

Rare earth elements (REEs) have been broad application in a range of industries, including the electronics industry, advanced materials, and medicine. However, health risks associated with REEs received increasing attention. 31 residents (16 males and 15 females) from Bayan Obo mining in Inner Mongolia, China, were enrolled in this study. In total, 677 food samples, the major human exposure matrices (drinking water and duplicate diets), and bio-samples (urine and blood) of 31 participants were obtained. The concentrations of REEs were measured to characterize their external and internal exposures, and the potential health risk of exposure to REE through the ingestion route was analyzed. The results revealed that the detection rate in blood samples (100%) is higher than in urine (32.86%), and only a few REEs were detected in water samples (8.06%), the urine concentrations were considerably lower than in blood. Exposure to REEs through drinking water was considered negligible compared to food intake. Lanthanum and cerium were the most concentrated REEs in food samples. Health risks were calculated based on a dose-response model, the total hazard quotients (THQ) values for all food groups were within normal levels, and the Monte Carlo simulation results show that the 5th, the 50th, and the 95th percentile values of HI were found as 1.45 × 10−2, 3.52 × 10−2, and 9.13 × 10−2, respectively, neither exceeds the threshold, indicating low health risks associated with food intake exposure for this area. The sensitivity results suggest that underweight people are at higher risk, cerium, lanthanum, and yttrium concentrations, and food intake contributes more to health risks. The use of probability distribution methods can improve the accuracy of the results. The cumulative health risk through food intake is negligible, and further attention should be paid to the health risk induced by other routes of exposure to REEs by the local residents.

Thermoelectric and Magnetic Properties and Electronic Structure of Solid Solutions CuCr1-xLaxS2

The oxidation states of atoms in CuCr1-xLaxS2 (x = 0–0.03) solid solutions were determined using the analysis of Cu2p, Cr2p, S2p, and La3d core level binding energy. The cationic substitution did not significantly affect the charge distribution on matrix elements (Cu, Cr, and S). The oxidation states of the atoms were identified as S2− for sulfur, Cu+ for copper, and Cr3+ for chromium. The cationic substitution in CuCr1-xLaxS2 was found to occur via the isovalent principle. The cationic substitution of CuCrS2 matrix with lanthanum ions led to the enhancement of the Seebeck coefficient comparing CuCr1-xLaxS2 to the initial matrix. The observed enhancement was attributed to the reconstruction of the valence band electronic structure after the cationic substitution. The maximum Seebeck coefficient value of 412 μV/K was measured for CuCr0.985La0.015S2 at 420 K. An increase in the lanthanum concentration to x = 0.03 caused a suppression of the Seebeck coefficient. The synthetic route was found to significantly affect both the magnetic properties and charge carrier concentration. The magnetic properties of CuCr1-xLaxS2 synthesized using metal sulfide reagents cannot be interpreted using the simple isovalent Cr3+ to La3+ cationic substitution model. The defectiveness of the samples and the formation of the impurity CuLaS2 phase could be additional factors that affect the magnetic properties of CuCr1-xLaxS2.

Improvement in ammonia gas sensing properties of La doped MoO3 thin films fabricated by nebulizer spray pyrolysis method

In the present work, different doping concentration (0, 1, 2, 3, 4 and 5 wt%) of Lanthanum (La) doped Molybdenum trioxide (MoO3) thin films were prepared using low cost Nebulizer spray pyrolysis (NSP)technique. The crystalline, morphology, optical and gas sensing properties of thin films were investigated. The presence of monoclinic MoO3 structure was confirmed through the XRD investigation for all the samples with highest crystallite of 61 nm was observed for 2 wt% La doped MoO3 thin film. The surface morphology of the produced thin films exhibits a reticulate nanofibrous mesh shape with increased particle size and porosity on addition of 2% La dopants in MoO3.The UV–Vis results showed the band gap values for the prepared thin films in the range 3.12–3.26 eV and the minimum bandgap was observed for the 2 wt% of La doped MoO3 thin film. Also the PL results confirmed the presence of more oxygen vacancies for the 2 wt% of La doped MoO3 thin film. The NH3 gas sensing study was conducted for the prepared films at room temperature, the 2 wt% of La doped MoO3thin film exhibits a maximum sensor response of 900, faster response times (28 s and 2.9s) compared to other fabricated devices. The results suggest that the 2% La doping in MoO3 could be an optimum doping concentration for the preparation of commercial NH3 gas sensors.

Potential for Phytomining of Rare Earth Elements by Naturally Occurring Plants in Reclaimed Tailing Ponds

Rare earth elements (REEs) from the ex-mining area (reclaimed tailing ponds) in East Rodope, Bulgaria, were investigated in soil and different plant species using inductively coupled plasma-optical emission spectrometry (ICP-OES). The tailings pond was reclaimed 20 years ago. The research work aims to determine the potential for phytomining of rare earth elements by naturally occurring plants in reclaimed tailing ponds. In the soil samples, the concentrations of cerium (Ce), lanthanum (La), and gadolinium (Gd) exceeded the average content of the elements in soils. The bioconcentration factor (BCF) was calculated. It was found that light rare earth elements (LREEs) are in greater concentration in plant samples than heavy rare earth elements (HREEs).

Figures of merit of PLZT ferroelectric ceramics for practical applications

Structural, microstructural and pyroelectric properties were investigated in PZT-based ferroelectric ceramics for a composition close to the morphotropic phase boundary (Zr/Ti = 53/47), as a function of the lanthanum content. The samples were prepared via the conventional solid-state reaction sintering method. Three compositions were synthetized and studied following the PbZr0.53Ti0.47O3 + x mole% La nominal formula, where x = 0.0, 2.5 and 5.0. The structural characterization confirmed the presence of both tetragonal and rhombohedral phases for all the studied compositions, showing a decrease in the tetragonality factor (c/a) with the increase of the lanthanum concentration. The observed decrease in the stability of the ferroelectric phase (in favor of the paraelectric one) have been discussed in light of the solubility of the doping cation into the studied PZT perovskite structure. Microstructural properties revealed low pores concentration micrographs, showing homogeneous microstructures and uniform grain-sizes. The pyroelectric response of the as-prepared PLZT samples was also investigated in a wide temperature interval. The lower lanthanum content composition exhibited the best properties, characterized by a high pyroelectric coefficient and enhanced figures of merit. These characteristics make such a composition a promising material for practical applications.

Effect of La doping on the structure and cycloidal spin ordering in multiferroic BiFeO3.

A series of Bi1-xLaxFeO3 samples with 0.00 ≤ x ≤ 0.30 was synthesized by the sol-gel method. The effects of lanthanum concentration on the phase formation, microstructure and cycloidal spin ordering were studied using X-ray diffraction, scanning electron microscopy and Mössbauer spectroscopy. The crystal structure of the La-doped bismuth ferrite transformed from rhombohedral R3c (x ≤ 0.05) to a mixture of R3c and cubic Pm3m (0.07 ≤ x ≤ 0.15) and finally to a mixture of R3c, Pm3m and orthorhombic Pbam (0.20 ≤ x ≤ 0.30). The Pbam phase, with characteristic porous microstructure shown by microscopy images, was observed in Bi1-xLaxFeO3 compounds for the first time. Based on the Mössbauer spectroscopy, it was found that the cycloidal spin ordering started to disappear at x = 0.07. With increasing La concentration the share of the cycloid decreased from 100% at 0.00 ≤ x ≤ 0.05 to 0% at x = 0.30. At the beginning, for x ≤ 0.02, the anharmonicity parameter, m, of the cycloidal spin ordering was about 0.5, which is typical of a pure BiFeO3 compound. In the range 0.05 ≤ x ≤ 0.25, the m parameter was of the order of 0.1, which indicated the practically harmonic character of the cycloid. The structural transition at x = 0.07 was accompanied by a substantial increase in magnetization.