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To study the synergistic lubricating effects of graphene oxide (GO) and lanthanum fluoride (LaF3), and find a new anti‐wear additive, oleic acid surface‐modified graphene oxide‐lanthanum fluoride (OA‐GO‐LaF3, OGL) composite nano‐additive was prepared by hydrothermal method by using oleic acid as the modifier. The morphology, structure, composition, element valence, thermal stability and tribological properties of nano additives were characterised by a series of modern characterisation methods. Results show that OGL has a higher degree of graphitization, smaller particle size, more homogeneous disperse, higher LaF3 load and stronger thermal stability than that of GL. The tribological properties of OGL which is modified by oleic acid are better than unmodified GL. Analysis of the friction mechanism shows that both OGL and GL can generate LaF3 physical adsorption films through adsorption during the friction process and tribochemical reactions film containing lanthanum compounds, carbon oxide compounds, and iron oxide compounds on the friction surface. These physical adsorption films and chemical reaction film can improve lubrication. [ABSTRACT FROM AUTHOR]

Coordination compounds of lanthanum with carbacylamidophosphate - N,N'-tetraethyl-N''-(trichloroacetyl)phosphortriamide (HL) and 2,2'-bipyridine (bipy) of composition LaLbipy2(NO3)2 and LaL3bipy were synthesized and studied by means of X-ray, thermal gravimetric analyses, IR, and NMR spectroscopy. It was established that all the ligands in the complexes are coordinated towards lanthanum in bidentate manner. Coordination number of central ion equals ten and eight for LaLbipy2(NO3)2 and LaL3bipy, respectively. Coordination polyhedron of LaIII ion has distorted geometry between bicapped square antiprism and sphenocorona in LaLbipy2(NO3)2 and between square antiprism and triangular dodecahedron in LaL3bipy. The bonds lengths La-O and La-N are commensurate in the synthesized complexes. The both structures are characterized by the presence of numerous intermolecular interactions, which have been analyzed using Hirshfeld surface tool. A feature of the complex LaLbipy2(NO3)2 is the presence of two crystallographically independent molecules in crystal. The compounds LaLbipy2(NO3)2 and LaL3bipy are thermally stable to 175°C and 165°C, respectively. A feature of the tris-complex LaL3bipy is the presence of a phase transition at a temperature of 96°C. [ABSTRACT FROM AUTHOR]

The prototype high-entropy oxide (HEO) Y0.2La0.2Ce0.2Pr0.2Sm0.2O2−δ represents a particularly complex class of HEOs with significant anion sublattice entropy. The system takes either a fluorite or bixbyite-type crystal structure, depending on synthesis kinetics and thermal history. Here, we synthesize bulk ceramics and epitaxial thin films of Y0.2La0.2Ce0.2Pr0.2Sm0.2O2−δ and use diffraction to explore crystal symmetry and phase. Thin films exhibit the high symmetry fluorite phase, while bulk ceramics adopt the lower symmetry bixbyite phase. The difference in chemical ordering and observed symmetry between vapor-deposited and reactively sintered specimens suggests that synthesis kinetics can influence accessible local atomic configurations, i.e., the high kinetic energy adatoms quench in a higher-effective temperature, and thus higher symmetry structure with more configurational entropy. More generally, this demonstration shows that recovered HEO specimens can exhibit appreciably different local configurations depending on synthesis kinetics, with potential ramifications on macroscopic physical properties. [ABSTRACT FROM AUTHOR]

In the present work, we have demonstrated a highly sensitive H2 gas sensor using a lanthanum doped ZnO (La_ZnO) thin film operated at 300 °C. Also, a p-type to n-type carrier reversal activity is revealed in the presence of H2 gas species, which predominantly depends on the operating temperature and doping concentration of lanthanum. Pure and La_ZnO (1–10 at. %) thin films were successfully synthesized using a sol-gel route, where a 5 at. % lanthanum doped ZnO thin film shows an outstanding H2 gas sensitivity (400%) among all other samples with an optimized temperature of 300 °C. Moreover, this sensor actively responds to a wide H2 gas concentration (10–500 ppm) with a sensitivity of 0.9 (∼n). Additionally, H2 gas sensing selectivity and mixed gas sensing performance were investigated in the presence of CO and CO2 gas species at optimized temperature (300 °C). Results show that the pure and 1–3 at. % La_ZnO thin films exhibited n-type H2 gas sensing, while p-type sensing behavior was observed for 5% and 10% La_ZnO thin films at 300 °C. It is further observed that O− species are extremely active to CO gas species operating at a high operating temperature (>250 °C). Therefore, despite the emerging p-type behavior of the sensor, the ejected electrons are expected to dominantly reduce the sensor resistance in the presence of CO gas species at 350 °C. The improvement of H2 sensing is further interrelated with the defect levels using Raman spectroscopy. [ABSTRACT FROM AUTHOR]

Due to the specific affinity of lanthanum (La) toward phosphate over a wide pH range, La compounds such as lanthanum oxide (LO), lanthanum hydroxide (LH), and lanthanum carbonate (LC) have been integrated into various La-based adsorbents in recent years. In order to evaluate the differences among LO, LH, and LC in terms of phosphate removal performance (adsorption capacity, pH-dependent behavior, and selectivity), stability (La leaching), and reusability, data from the literature are consolidated. Furthermore, key properties of the respective compounds such as solubility and speciation are examined to identify possible underlying reasons. LC exhibits superior adsorption capacity and a wider optimum pH range for phosphate binding and lower La leaching, but reusability data of the various compounds remain inconclusive. Based on their superior performance and stability in laboratory studies, LC may have greater lifespan and can serve as a viable alternative to LO and LH for future studies on phosphate removal in order to maximize phosphate removal efficiency while simultaneously reducing secondary pollution. To further develop La-based adsorbents for phosphate removal and recovery, direct comparisons are needed among La compounds using more complex matrices such as wastewater and river water. Furthermore, the role of crystal structure in the phosphate removal performance of different compounds must be carefully assessed. Finally, to evaluate the feasibility of practical application and understand the effects of continuous flow operation on phosphate removal and recovery efficiency, more pilot-scale studies involving La-based adsorbents should be conducted. Performance, stability, and reusability of different La compounds are crucial to the practicability of La-based adsorbents for phosphate removal along with addressing key challenges associated with real-world usage. The simultaneous incorporation of other metals presents a possible way to improve on the inherent properties of La-based adsorbents to enable them to better address these challenges. [ABSTRACT FROM AUTHOR]

In the model manganese perovskites La1−xCaxMnO3, several important phenomena have been observed, including ferromagnetic metallic/insulating states, colossal magnetoresistance effects, and charge- and orbital-ordered states. In the past, only compounds with x = 1/2, 2/3 and 3/4 and an insulating ground/antiferromagnetic state have been studied. To fully understand the crystal and electronic structures of these materials, it is important to study compounds with doping levels in the range of 0.5 < x < 2/3. Here we study the crystal structure in a series of compounds with 0.5 < x ≤ 0.6 using ultrahigh-resolution synchrotron X-ray diffraction. The experimental results reveal that all compounds undergo a structural transition at T < TCO(x) ≈ 200 − 220 K with the concomitant emergence of superlattice Bragg peaks, which can be indexed assuming a superstructure with a modulation propagation vector, τ. At the base temperature of 5 K, the modulation vector of the superstructure τ = [τa, 0, 0] is parallel to the a-axis, with τa varying linearly with x, as τa ≈ 1 − x. Our results may aid attempts to understand more deeply phenomena related to spin, charge, and orbital ordering, as well as colossal magnetoresistance and symmetry breaking and emergent order in quantum states. Doped lanthanum manganite compounds exhibit a range of conducting, electronic and magnetic phases, and, in the case of the Ca-doped series, a phase transition from a ferromagnetic metal to an antiferromagnetic insulator occurs. Here, the authors use ultrahigh-resolution synchrotron X-ray diffraction to track the complex structural behavior of La1−xCaxMnO3 below the charge-ordering temperatures. [ABSTRACT FROM AUTHOR]

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A series of LaF3:Ce3+ phosphors for application in photodynamic therapy are synthesized using a one-stage solvothermal synthesis. The synthesis conditions; type and quantity of stabilizer; concentration of activator providing the maximum intensity of UV- and X-ray-excited luminescence; lowest size; and highest colloidal stability of the phosphor nanoparticles are found. As a result of this study, the following parameters are determined using cerium content 5% mol. ethanol as the reaction medium for the solvothermal synthesis and polyvinylpyrrolidone as the stabilizer at an optimized amount. [ABSTRACT FROM AUTHOR]

We report on the thermoelectric properties of strained, highly-oriented, lightly-doped La1–xSrxCoO3 thin films, grown on MgO (100) substrates by pulsed laser deposition. The large lattice mismatch (∼9%), along with the different thermal expansion coefficients, between La1–xSrxCoO3 and MgO, result in the incoherent growth of thin films and the generation of a tensile thermal strain (∼1%). Room temperature resistivity values of the films are similar to those of bulk samples, while the temperature dependence of resistivity of the films does not seem to be affected by the thermal strain. The Seebeck coefficient values of all investigated films are positive but lower than those of their bulk counterparts, throughout the measured temperature range. The lower values of the films' Seebeck coefficient are attributed to the stabilization of mixed Co spin state configuration, which is induced by the thermal strain. As a result of the reduced Seebeck coefficient values, the thermoelectric power factor is suppressed, suggesting that the tensile thermal strain does not favor the thermoelectric behavior of the La1–xSrxCoO3. [ABSTRACT FROM AUTHOR]

LaSb2 has a layered crystal structure along the c-axis with ∼2% difference between the in-plane orthorombic a and b axes. Here, we report on the thermal conductivity, electrical resistivity, and Seebeck coefficient from 10 to 300 K as well as the magnetoresistance at 10 K. Using the van der Pauw technique on single crystal samples, the in-plane electrical resistivity tensor has been measured and it is found to be isotropic. An anisotropic crystal structure may have isotropic properties, but in the present case, the isotropic nature stems from crystal imperfection. Single crystal X-ray diffraction provides evidence of a mixing of the in-plane a- and b-directions leading to observed diffraction intensity where systematic absences are expected. Whether the underlying structural mechanism is twinning or stacking faults is unknown, but it could be the origin of the previously observed charge density wave states, and it may also explain the high unsaturating linear magnetoresistance reported here. At ambient conditions, LaSb2 is found to be stable in air, with no sign of bulk degradation after 5 years of storage; however, some change is observed in the amorphous background scattering. [ABSTRACT FROM AUTHOR]

We systematically investigate the thermoelectric properties of lanthanum phosphide (LaP) using first-principles calculations together with the Boltzmann transport theory. The dynamic stability of LaP is confirmed based on phonon dispersion. The different atomic masses of La and P atoms lead to an acoustic-optical bandgap that prohibits scattering between acoustic and optical phonon modes. The lattice thermal conductivity κ l is 3.19 W/mK at room temperature, which is less than that of LaAs because of the smaller group velocities and the larger Grüneisen parameter. The calculated phonon-mode contribution to κ l , scattering rate, and mean free path may provide significant guidance to further theoretical and experimental research. The power factor reaches 0.012 W m−1 K−2 at a carrier concentration of 1.05 × 10 20 c m − 3 , which is comparable to the power factor of the typical thermoelectric material Bi2Te3. This reasonable power factor and thermal conductivity suggest that LaP is a promising thermoelectric material. The dependence of the figure of merit ZT on carrier concentration n and temperature T indicates that a high ZT can be obtained by increasing the temperature and tuning the carrier concentration. [ABSTRACT FROM AUTHOR]

(Sr 0.95 La 0.05) 0.95 □ 0.05 TiO 3 ceramics were prepared by solid state reaction and sintered by spark plasma sintering at different temperatures ranging from 1473 to 1873 K for 10 min. The thermoelectric properties show that sintering at temperatures higher than 1773 K allows reaching high thermoelectric properties similar to the ones obtained after annealing at high temperatures in H 2 / N 2 for several hours. The high temperature sintered samples exhibit highest power factor near room temperature, resulting in ZT values higher than 0.1. Therefore, the 10 min short SPS process at high temperatures described in this paper is an easy, cheap, fast, and one step route to obtain dense and efficient SrTiO 3 -based thermoelectric ceramics. However, SEM observations show that the samples are not pure perovskite phase but contain titanium oxide and lanthanum compound aggregates. [ABSTRACT FROM AUTHOR]

Temperature is one of the key factor that affecting the electrical, physical, structural, and morphological properties as well as the crystallinity of the nanomaterials. The current study investigates the effect of annealing temperature on the structural and electrical properties of lanthanum oxide (La2O3) thick films. La2O3 thick films were prepared on a glass substrate using a conventional screen printing technique. In this work, T1 is an unannealed prepared film, whereas T2 and T3 are annealed in a muffle furnace for 3 hours at 350°C and 450°C, respectively. XRD technique was exploited to investigate the crystallization behavior of the films. It was found that the crystal structure of La2O3 thick films are pure hexagonal phase. The annealing temperatures were revealed to have influence on the crystallite sizes of the films. SEM and EDS was used to study the morphology and elemental analysis of the films respectively. The electrical properties of the films were explored by measuring resistivity, temperature coefficient of resistivity (TCR), and activation energy at lower and higher temperatures regions. The film annealed at 450°C has high resistivity, a high TCR, and small crystallite size. The thickness of the La2O3 thick films was also found to decrease as the annealing temperature increased. [ABSTRACT FROM AUTHOR]

Lanthanum manganite (LMO) thin films were deposited by co-sputtering La and Mn targets in an Ar and O2 gas mixture. The films were synthesized on silicon and fused silica substrates. The influences of thermal annealing on the structure, optical and electrical properties of LMO films were investigated. The results exhibited a correlation between these properties. In the amorphous state, an increase in annealing temperature improved the optical transmission and decreased the electrical capacitance. The beginning of crystallization at 600 °C was manifested by a strong increase in the capacitance and a decrease in the optical transmission. At higher annealing temperature, polycrystalline films were obtained with different optical and electrical characteristics. On the other hand, the annealed LMO films showed a photocurrent effect during exposure to a weak LED light. [ABSTRACT FROM AUTHOR]

We experimentally investigated the photo-induced direct current (DC) drift of a lead lanthanum zirconate titanate (PLZT) Mach-Zehnder modulator with large optical input power. We clarify the mechanism by which short-term and long-term DC drifts arise and discuss each case of DC drift. We reveal that short-term DC drift can be reduced by adjusting the buffer-layer resistivity of the PLZT modulator. We also found that the impurity level of the buffer layer affects long-term DC drift. [ABSTRACT FROM AUTHOR]

Rotations and distortions of oxygen octahedra in perovskites play a key role in determining their functional properties. Here, we investigate how octahedral rotations can couple from one material to another in La2/3Sr1/3MnO3/SrTiO3 epitaxial heterostructures by first principles density functional theory calculations, emphasizing the important differences between systems oriented perpendicular to the (111)- and (001)-facets. We find that the coupling length of out-of-phase octahedral rotations is independent of the crystalline facet, pointing toward a steric effect. However, the detailed octahedral structure across the interface is significantly different between the (111)- and (001)-orientations. For (001)-oriented interfaces, there is a clear difference whether the rotation axis in SrTiO3 is parallel or perpendicular to the interface plane, while for the (111)-interface, the different rotations' axes in SrTiO3 are symmetry equivalent. Finally, we show that octahedral coupling across the interface can be used to control the spatial distribution of the spin density. [ABSTRACT FROM AUTHOR]

We have investigated the electrical and dielectric properties of rare earth perovskites-type oxide (LaErO3 and LaHoO3) by using impedance spectroscopy, respectively, over a frequency and temperature range of [0.6 kHz–8MHz] and [673–973 K]. Both oxides crystallize in the orthorhombic structure but exhibit difference in lattice distortions. A correlation between structural properties and dielectric anisotropies is carried out. The analysis of Nyquist semicircles confirms the presence of bulk effects and non-Debye relaxation processes for both compounds. The activation energy, calculated using relaxation time and direct current conductivity models, was found to follow the Arrhenius law. The frequency dependence of alternative current conductivity is described by Jonscher’s universal power law and shows that the conduction mechanism follows the non-overlapping small polaron tunneling model. The investigation of dielectric properties revealed that at low frequencies the dielectric constant was higher for LaHoO3 oxide than that for LaErO3. Modulus formalism examination demonstrates that the relaxation process of studied materials takes place via the hopping mechanism. [ABSTRACT FROM AUTHOR]

Using a variety of physicochemical characterization techniques, we have determined the composition and chemical formula of lanthanum and neodymium compounds with phthalic acid, synthesized for the first time. The compounds have been shown to have similar chemical formulas: La2(L)3·7H2O and Nd2(L)3·6H2O. We have examined the thermal destruction of the synthesized compounds. The proposed schematic structure of the La complex consists of zigzag 2D polymer layers, which are cross-linked by water molecules to form a 3D structure—a supramolecule. [ABSTRACT FROM AUTHOR]

A significant structural modification and enhancement of the electrical and magnetic properties with dilute substitution of Zr (≤1mol.%) in the Bi0.8La0.2Fe1-xZrxO3 system has been reported. A mixture of rhombohedral and orthorhombic phases was detected in these conventionally sintered ceramics. Transition from a leaky state to an insulating state was observed upon Zr substitution. This is the first time that a drop in the electrical conductivity as large as 6 orders of magnitude for doping as small as 0.25mol. % in bismuth ferrite systems has been reported. An investigation on the nature of this abrupt transition revealed the dominant role of defects. A proper consideration of possible defect reactions taking place during and after sintering satisfactorily accounts for the observed modulation in the electrical properties. Both AC and DC measurements indicate that, before Zr substitution, ptype hopping conduction prevails with an activation energy as low as ~0.57 eV, whereas the Zr substitution makes oxide ion migration the central mechanism for conduction with the activation energy of ~0.96-1.08 eV. In contrast to that, the magnetic properties of the compounds experience a more subtle effect; a gradual modification of saturation magnetization and coercivity with Zr substitution is observed. Curve fitting of the magnetic hysteresis loops not only allowed extraction of three separate contributions from the magnetic response but also helped to explain the effects of Zr on the magnetic properties. Modifications of structural characteristics and magnetic anisotropy of the samples are believed to be the primary driving force behind the improvement in the magnetic properties. [ABSTRACT FROM AUTHOR]

The systematic study on structural properties of Ba-substituted La0.9Sr0.1Al0.9Mg0.1O3-δ and its correlation with conductivity was carried out. X-ray diffraction patterns indicated that the system formed a single phase composition up to 3% of Ba double substitution at the La-site. Energy dispersive X-ray spectroscopy and XPS results confirmed elemental compositions and revealed the maximum deficiency in oxygen for the 3% Ba-substituted sample. Dense grain formation is observed in SEM images, complementing higher density of these samples (>93%). Electrical conductivity was found to be in correlation with a new structural parameter of the critical triangle of (La/Sr/Ba)- Al/Mg-(La/Sr/Ba). The value of conductivity increased by an order of 2 in a substituted sample as compared to pure LaAlO3. The activation energy can be correlated with the area of the critical triangle of (La/Sr/Ba)-Al/Mg-(La/Sr/Ba). The migration path for ionic conduction of the oxygen ion was mapped out using the correlation of bulk conductivity with the A-A-B angle (β) and dc conductivity with the A-B-A angle (α). [ABSTRACT FROM AUTHOR]

The two non‐isostructural lanthanum pnictogenide selenides La3NSe3 and La3PSe3 are formed by oxidizing lanthanum metal with sodium azide (NaN3) in the presence of selenium and an excess of iodine for eight days at 850 °C and by reacting the two binary compounds lanthanum sesquiselenide (La2Se3) and lanthanum monophosphide (LaP) for four days at 900 °C in torch‐sealed glassy silica ampoules. La3NSe3 crystallizes with the well‐known Sm3NS3‐type structure in the orthorhombic space group Pnma with the lattice parameters a=1278.56(8) pm, b=424.18(3) pm, c=1358.73(9) pm, while La3PSe3 adopts the cubic Th3P4‐type structure in the space group I4‾3d with the lattice parameter a=901.42(6) pm, both for Z=4. It features one crystallographically distinct cationic La3+ site and a mixed anionic site with both P3− and Se2− anions sharing the same crystallographic position in its crystal structure. In contrast, the crystal structure of La3NSe3 is comprised of three different La3+ cations with one N3− and three distinct Se2− anions. The key structural elements are N3− centered (La3+)4 tetrahedra connected via vertices to form one‐dimensionally infinite chains ∞1{[N(La1,2)2/1t(La3)2/2v]6+} (t=terminal, v=vertex‐sharing). The comparatively large La3+ cation adopts coordination numbers of six (1×) and seven (2×) in La3NSe3, whereas in La3PSe3, the coordination number of the single cation site is eight. [ABSTRACT FROM AUTHOR]

Tunable liquid crystal (LC) alignment with twisted nematic (TN) and vertical alignment (VA) driving modes is achieved by a convenient brush‐coating method. The brush‐coating process combines film deposition and alignment treatment processes, and lanthanum aluminum zirconium zinc oxide (LaAlZrZnO) is used for the LC alignment layer. X‐ray photoelectron spectroscopy results confirm LaAlZrZnO film formation with fine optical transparency. Atomic force microscopy and line profile data indicate nano/micro surface structure with dense or directional morphologies induced by shear stresses according to film curing temperature. Low‐temperature‐cured films exhibit hydrophobic properties with low surface energy, whereas high‐temperature‐cured films show hydrophilicity with high surface energy. The geometric constraints and chemical affinities of the films induce homeotropic and homogeneous LC alignments on the surface according to the film curing temperature, respectively. The LC alignment state is verified by polarized optical microscopy and pretilt angle analysis. The brush‐coated LaAlZrZnO film demonstrates high thermal budget for advanced LC systems. The VA‐mode and TN‐mode LC cells based on the LaAlZrZnO film enable high electro‐optical performances and low power consumption. Therefore, the brush‐coating method is expected to be adoptable for next‐generation LC device applications. [ABSTRACT FROM AUTHOR]

We have presented the structural, elastic, electronic, phononic, and electron-phonon interaction properties of the La-based noncentrosymmetric superconductors, such as LaIrSi3, LaRhSi3, and LaPdSi3, by using the generalized gradient approximation of the density functional theory. The calculated elastic constants reveal the mechanical stability of all the studied compounds in their noncentrosymmetric structure, while the lack of inversion symmetry gives rise to lift the degeneracy of their electronic bands, except in the Γ-Z and X-P directions. The calculated Eliashberg spectral function shows that all phonon branches of these materials couple considerably with electrons, and thus, all of them make contribution to the average electron-phonon coupling parameter λ. Using the calculated values of λ and the logarithmically averaged phonon frequency ωln, the superconducting critical temperature Tc values for LaIrSi3, LaRhSi3, and LaPdSi3 are estimated to be 0.89, 2.56, and 2.40 K, respectively, which accord very well with their corresponding experimental values of 0.77, 2.16, and 2.60 K. [ABSTRACT FROM AUTHOR]

La2Mo2O9 (LMO) thin films have been deposited on Pt/Ti/SiO2/Si substrates by pulsed laser deposition and the resistive switching (RS) characteristics of the Au/LMO/Pt devices has been investigated. The Au/LMO/Pt devices show excellent unipolar RS characteristics with high resistance ratio between high resistance state and low resistance state (LRS), good endurance, and retention performances. The results of temperature dependence of resistance and x-ray photoelectron spectroscopy suggest that the observed RS characteristics can be explained by the formation and rupture of conducting filaments composed of oxygen vacancies. Furthermore, the plot of the reset current (IR) as a function of the third harmonic coefficient (B0) caused by Joule heating during the reset process shows scaling behavior with a power law of IR∝ B0-δ. The IR and reset power (PR) can also be scaled to the resistance in LRS (R0), i.e., IR(PR) ∝ R0-α(β). The observed scaling behaviors indicate the importance of the Joule heating for the RS characteristics of Au/LMO/Pt devices. These results demonstrate the potential application of LMO thin film in a nonvolatile memory device. [ABSTRACT FROM AUTHOR]

Water pollution is a serious global environmental problem as many pollutants are highly carcinogenic to humans (e.g., arsenic) and cause disruption in the ecosystem (e.g., phosphorus for eutrophication). Therefore, development and application of cost-effective technologies are of great importance to meet the increasing stringent regulations and the greater challenges in the water contamination. This article provides a comprehensive review of publications in lanthanum (La)-based adsorbents that are exceptionally effective for the removal of several common inorganic contaminants from aqueous solutions. The abilities of lanthanum compounds (e.g., La2(CO3)3) as standalone adsorbents or La-incorporated adsorbents (e.g., with activated carbons) were summarized and discussed in detail. The reported studies have demonstrated that the lanthanum compounds particularly work well in the adsorption of inorganic anions (e.g., arsenic and fluoride). In addition, the incorporation of lanthanum onto some supporting materials would result in better adsorption with a lower material cost, due to better dispersion of lanthanum and well distributed active functional groups. The mechanisms of adsorption mainly include ligand exchange, surface complexation and electrostatic attraction. Various evidences given in the literatures demonstrate that, the La-based adsorbents are commercially viable and well outperform the commercial materials (e.g., ion exchange resins, activated carbons and iron oxides) for the water and wastewater treatment, in particular for the removal of anionic pollutants. [ABSTRACT FROM AUTHOR]

The chemical bath deposition technique was employed to synthesize unsubstituted and different percentages of La-substituted ZnO-nanoscaled thin films on a glass substrate with nominal concentrations of 0.0%, 3%, and 7%. Microwave irradiation effects on the photocatalyst of La-substituted ZnO samples for photodegradation of Congo red dye were investigated. Crystallographic parameters of unsubstituted and La-substituted ZnO were scrutinized by XRD. It was verified that as-synthesized samples belong to the wurtzite structure. Chemical stretching of the as-prepared samples was detected using an FTIR spectrum which reflects that La substitutes in ZnO lattice. A peak of 1630 cm−1 is presently owing to the ZnO stretching and deformation. The band gap of unsubstituted and La-substituted ZnO was evaluated using a UV–Vis spectrometer, and it was substantiated that the energy band gap suppresses as La content enhances which states the existence of red shift. The electric property such as resistance of unsubstituted and La-substituted ZnO nanomaterial was intended by I–V characteristics. The optical property with surface defect study was elucidated by fluorescence spectroscopy. Visible light photosensitivity was intended by I–V characteristics. [ABSTRACT FROM AUTHOR]

In the present work, LaNi0.5Ti0.5O3 and La2NiTiO6 nanoparticles were synthesized by the modified Pechini method. LaNi0.5Ti0.5O3 was calcined at 1073 K for 17 h or 100 h, while La2NiTiO6 was calcined at 1273 K for 135 h. The double perovskite calcined at 1073 K for 17 h presented orthorhombic symmetry with Pbnm space group, mean particle size was 31.9 ± 1 nm, random ordering of Ni2+ and Ti4+ cations, Néel temperature close to 15 K, and magnetic moment of 1.29 μ B . By increasing the calcination time, this material showed the same symmetry and space group, a mean particle size of 50.7 ± 2 nm, short-range ordering of Ni2+ and Ti4+ cations, Néel temperature around 12 K, and magnetic moment of 0.96 μ B . La2NiTiO6 presented a monoclinic crystal structure, with P21/n space group, mean particle size of 80.0 ± 5 nm, rock salt ordering of Ni2+ and Ti4+, Néel temperature of approximately 23 K, and magnetic moment of 2.75 μ B . [ABSTRACT FROM AUTHOR]

Herein, a systematic study of postdeposition annealing for La1−xSrxMnO3 (LSMO) films regarding their structural, electronic, (magneto‐)optical, and magnetic properties is presented. The samples are prepared by magnetron sputtering at room temperature on silicon (111) substrates with native oxide and are annealed in ambient atmosphere for 12 h in a temperature range from 600 to 875 °C. The stoichiometry of the films is investigated by X‐ray photoelectron spectroscopy (XPS), and Raman spectroscopy is utilized to investigate the vibrational modes of the films. The diagonal and off‐diagonal components of the dielectric tensor are investigated by variable‐angle spectroscopic ellipsometry and magneto‐optic Kerr effect (MOKE) spectroscopy, respectively. The remanence and the coercive field of the layers are characterized by superconducting quantum interference device (SQUID) magnetometry. The magnetic properties are found to improve with increasing annealing temperature up to 850 °C, whereas the resistivity remains within a range between 0.5 and 2 Ωcm. The highest suitable annealing temperature for applications is, however, 775 °C due to the formation of a diffusion layer between LSMO and silicon oxide at higher temperatures. [ABSTRACT FROM AUTHOR]

The electrical transport properties of La1-xSrxCoO3 (LSCO) thin films were investigated in this paper. As x increased up to 0.3, the electrical transport mechanism transferred from variable range hopping to double-exchange and the film simultaneously turned from an insulator into a conductor. Different from the bulk materials, the maximum conductivity of the film appeared at x=0.3. A novel electrical transport model was proposed to explain this unconventional phenomenon. Besides, the effects of doped Sr and oxygen vacancies on the electrical transport properties were clarified by investigated the transport behaviors of the LaCoO3, La0.7S0.3CoO3, and La0.7S0.3CoO3-ω films. We found that, when Sr was doped into the LaCoO3 film, the insulating film turns into a conductor; when oxygen atoms were removed from the La0.7S0.3CoO3 film, the conducting film goes back to an insulator. Our work could shed light on the electrical transport mechanism of the LSCO films. [ABSTRACT FROM AUTHOR]

Polystyrene film nanocomposites of 0.3mm thickness with embedded LaPO4-Pr nanoparticles (40 wt. %) have been synthesized. The luminescent and kinetic properties of these polystyrene composites with embedded LaPO4-Pr nanoparticles upon pulse X-ray excitation have been studied. The luminescence intensity of this polystyrene material significantly increases as it is loaded with inorganic LaPO4-Pr nanoparticles. Nanocomposite films reveal luminescence spectra typical for polystyrene activators (p-Terphenyl and POPOP) and two components of decay time kinetics of luminescence with 12 ns and 2.8 ns time constants, depending on nanoparticle sizes. The component with 12 ns decay constant arises due to the radiative transfer of the 5d-4f-emission of the Pr3+ ions in the LaPO4 nanoparticles to the polystyrene. The decay component with the time constant 2.8 ns originates from luminescence of polystyrene matrix excited by electrons emitted from nanoparticles due to the photoeffect. This nonradiative mechanism of energy transfer from nanoparticles to polystyrene matrices is determinative for nanoparticles, as their sizes are smaller than a mean free path of an electron. [ABSTRACT FROM AUTHOR]

The La-excess alloys La1+δ(Fe0.85Si0.15)13 (d=0.06 and 0.09) exhibit large magnetocaloric effect which has been attributed to the occurrence of itinerant-electron metamagnetic transition near the Curie temperature TC. The maximum entropy change -ΔSm was shown to be from 4.5 to 11.5 J/kg K for the applied field variation ΔH from 20 to 70 kOe, respectively. The estimated relative cooling power for ΔH=70 kOe was 418 J/kg. The alloys show a typical NaZn13-type cubic structure, featuring a doping-induced magnetovolume effect with the increase in TC. Under the applied pressure up to 2 GPa, the TC as deduced from resistance measurements decreased linearly, ΔTC=113 (for δ=0.06) and 111K (for δ=0.09), together with a corresponding decrease of resistivity, Δp=6.1 µΩ m at room temperature for both samples. At a low pressure, the effect of spontaneous magnetostriction on TC caused by applying the pressure appeared to have a similar magnitude to that of the negative magnetovolume effect caused by La-excess doping. In comparison with other stoichiometric La(Fe1-xSix)13 compounds, the pressure in our case was shown to have a smaller influence on TC. [ABSTRACT FROM AUTHOR]

A series of LaAlO3 thin films with different thicknesses were deposited by pulsed laser deposition at temperatures from 720 °C to 800 °C. The results from grazing incidence x-ray diffraction and reciprocal space mapping indicate that a thin layer of LaAlO3 adjacent to the SrTiO3 substrate remains almost coherently strained to the substrate, while the top layer starts to relax quickly above a certain critical thickness, followed by a gradual relaxation at larger film thickness when they are grown at lower temperatures. The atomic force microscopy results show that the fast relaxation is accompanied by the formation of cracks on the film surface. This can be ascribed to the larger energy release rate when compared with the resistance of LaAlO3 to cracking, according to calculations from the Griffith fracture theory. For films grown at 720 °C, a drop in sheet resistance by two orders of magnitude is observed when the top layer starts to relax, indicating a relationship between the strain and the conductivity of the two-dimensional electron gas at the LaAlO3/SrTiO3 interface. The strain engineered by growth temperature provides a useful tool for the manipulation of the electronic properties of oxide heterointerfaces. [ABSTRACT FROM AUTHOR]

LaB6 nanoparticles are widely used as solar control materials for strong near-infrared absorption and high visible transparency. In order to elucidate the origin of this unique optical property, first-principles calculations have been made for the energy-band structure and dielectric functions of RIIIB6 (RIII = Sc, Y, La, Ac). On account of the precise assessment of the energy eigenvalues of vacant states in conduction band by employing the screened exchange method, as well as to the incorporation of the Drude term, dielectric functions and various physical properties of LaB6 have been reproduced in excellent agreement with experimental values. Systematic examinations of dielectric functions and electronic structures of the trivalent metal hexaborides have clarified the origin of the visible transparency and the near-infrared plasmon absorption of RIIIB6 nanoparticles. [ABSTRACT FROM AUTHOR]

Studying the adsorption of water on the metallic LaMnO3 surface can provide insight into this complicated surface-adsorbate interaction. Using density functional theory, we investigated the adsorption of a water monomer, dimer, trimer, and a monolayer on the surface. The electronic structure of ground state configurations is explored using analysis of density of states, charge density, and crystal orbital overlap populations. We found that the interaction between the surface and water molecules is stronger than hydrogen bonding between molecules, which facilitates wetting of the surface. Adsorbed water molecules form very strong hydrogen bonds, with substantially shifted OH stretch modes. For the monolayer of adsorbed water, a hint of a bilayer is observed with a height separation of only 0.2 Å. However, simulated scanning tunneling microscopy images and vibrational spectra suggest a significant difference between the two layers due to intermolecular bonding and interaction with the substrate. [ABSTRACT FROM AUTHOR]

Aluminoborosilicate glasses containing relatively high field strength modifiers (Ca, La, and Y) have been compressed at pressures up to 3 GPa and near the glass transition temperature (Tg) and quenched to room temperature at high pressure followed by decompression. Structural changes were quantified with high-resolution 27Al and 11B MAS nuclear magnetic resonance at 14.1-18.8 T. The changes with pressure in Al and B coordinations in the recovered samples are quite large with more than 50% decreases in tetrahedral aluminum (IVAl) and 200%-300% increases in tetrahedral boron (IVB). Glasses with higher field strength modifiers (La and Y) contain more high coordinated aluminum (V,VIAl) at all pressures studied. More high coordinated boron also correlates with higher field strength modifier if all three compositions are compared on an isothermal basis. Although lowering fictive temperature and increasing pressure both increase Al and B coordinations, our study shows that the actual mechanisms for structural changes are most probably different for temperature and pressure effects. Using a rough thermodynamic model to extrapolate to higher pressures, it appears that a simple non-bridging oxygen (NBO) consumption mechanism is not sufficient to convert all the aluminum to octahedral and boron to tetrahedral coordination, suggesting other mechanisms for structural changes could occur at high pressure as NBO becomes depleted. [ABSTRACT FROM AUTHOR]

Ionically conducting lanthanum fluoride (LaF3), displaying a nanoscopic lamellar structure, has been synthesized at the surface of an aqueous solution of LaCl3 and HF. The structure and the chemical composition of the conductor have been analyzed by SEM, electron probe microanalysis, X-ray powder diffraction, FTIR, and 19F magic angle spinning nuclear magnetic resonance (NMR) spectroscopy. The fluorine dynamics have been studied by NMR diffusometry and relaxometry in a temperature range from room temperature up to 875 K. The fluorine self-diffusion coefficient of the nanostructured LaF3 is about two orders of magnitude larger than that of bulk LaF3. This novel material is highly promising for many typical applications of fluorine ionic systems. [ABSTRACT FROM AUTHOR]

Wastewater treatment via photocatalytic activity is one of the most economical and environment-friendly method. However, obtaining an efficient photocatalyst remains a challenge for researchers in this most emerging field. In this study, pure and lanthnum (La)-(1%,2% and 3%) doped zinc oxide nanoparticles (ZnO-NPs) were synthesized via sol gel chemical technique to investigate their optical, chemical and structural properties. The synthesized NPs were characterized by using UV/VIS, SEM, EDS, XRD, FTIR, PL and Raman spectroscopy. Such nanoparticles (NPs) have been used as a photocatalyst for the degradation of rhodamine B (RhB) dye. Quite interestingly, the La-doped ZnO-NPs show unique results associated with the fact that by varying the concentration of dopant, the particle size is reduced (28.09 ± 0.04 nm to 15.85 ± 0.02 nm), which leads to a decrease in band gap, i.e., shifting toward visible (3.26 eV to 3.06 eV). This attributes to the fact that doping also helps to reduce electron–hole pair recombination rate during photocatalysis, which makes La-doped ZnO-NPs the most potential photocatalyst against RhB dye. We report a maximum degradation efficiency of 84.97% in 150 min observed from La0.02Zn0.98O, which reveals that 2% doping of La is the optimal value whereas further increase in concentration, i.e., at 3% (La) band gap increases whereas degradation efficiency reduces from 84.97 to 73.37%. [ABSTRACT FROM AUTHOR]

We studied the resistive memory switching in pulsed laser deposited amorphous LaHoO3 (a-LHO) thin films for non-volatile resistive random access memory applications. Nonpolar resistive switching (RS) was achieved in Pt/a-LHO/Pt memory cells with all four possible RS modes (i.e., positive unipolar, positive bipolar, negative unipolar, and negative bipolar) having high RON/ROFF ratios (in the range of ~104-105) and non-overlapping switching voltages (set voltage, VON~±63.6-4.2V and reset voltage, VOFF~±1.3-1.6V) with a small variation of about 65-8%. Temperature dependent current-voltage (I-V) characteristics indicated the metallic conduction in low resistance states (LRS). We believe that the formation (set) and rupture (reset) of mixed conducting filaments formed out of oxygen vacancies and metallic Ho atoms could be responsible for the change in the resistance states of the memory cell. Detailed analysis of I-V characteristics further corroborated the formation of conductive nanofilaments based on metal-like (Ohmic) conduction in LRS. Simmons-Schottky emission was found to be the dominant charge transport mechanism in the high resistance state. [ABSTRACT FROM AUTHOR]

Correlation of structure and ion conduction of La2-xYxMo2O9 (0≤x≤0.2) has been investigated. The cubic symmetry with space group P213 and other structural parameters are obtained from Rietveld refinement of X-ray diffraction patterns of Y doped samples. The average lanthanum-oxygen and molybdenum-oxygen distances are obtained from the electron density contour plot. The transmission electron microscopic study confirms the cubic nature of the samples and also provides an estimate of thickness of the grain boundary. The scanning transmission electron microscope energy dispersive spectrometer mapping confirms the different orientations of grains. The composition dependence of the ionic conductivity has been correlated with that of O2 and O3 site occupancies in the [O1La3Mo] antitetrahedral unit. The different vibrational modes in the low frequency region due to vibration of Mo-O bands are confirmed from the analysis of FTIR and Raman spectra. The full widths at half maximum of most of the Mo-O bands are found to be independent of Y doping. Additionally, the shifts in the position of Raman bands are correlated with unit cell parameter using Grüneisen constant [ABSTRACT FROM AUTHOR]

The characteristic peaks (pre-edge peaks) in the La L1-edge X-ray absorption near edge structure (XANES) of various La complex oxides were analyzed by both experimental and theoretical approaches. The pre-edge peak areas are correlated with the bond angle analysis (BAA) parameter, which we proposed as an indicator of the centrosymmetry or disorder of the local configuration of the La site. The origin of the pre-edge peak and the parameterization criteria of the BAA parameter were evaluated using theoretical calculations based on molecular orbital theory and multiple scattering theory. The theoretical calculations showed that the origin of the pre-edge peak at the La L1-edge is electric dipole transition from 2s to unoccupied states generated by p-d hybridization. Medium-scale theoretical simulations of the La L1-edge XANES spectra of thousands of virtual La aqueous complex models verified that the parameterization criteria of the BAA parameter are applicable to local configuration analysis of La. [ABSTRACT FROM AUTHOR]

We investigate magnetoresistance, ρc, of single-crystal bilayer lanthanum manganites (La1-zNdz)1.4Sr1.6Mn2O7 (z=0 and 0.1) at a transport current flowing along the crystal c axis and in external magnetic fields applied parallel to the crystal c axis or ab plane. It is demonstrated that the La1.4Sr1.6Mn2O7 manganite exhibits the positive magnetoresistance effect in the magnetic field applied in the ab sample plane at the temperatures T<60 K, along with the negative magnetoresistance typical of all the substituted lanthanum manganites. In the (La0.9Nd0.1)1.4Sr1.6Mn2O7 sample, the positive magnetoresistance effect is observed at temperatures of 60-80K in an applied field parallel to the c axis. The mechanism of this effect is shown to be fundamentally different from the colossal magnetoresistance effect typical of lanthanum manganites. The positive magnetoresistance originates from spin-dependent tunneling of carriers between the manganese-oxygen bilayers and can be explained by features of the magnetic structure of the investigated compounds. [ABSTRACT FROM AUTHOR]

In this paper, we present the results of an experimental investigation on the magnetocaloric properties of hydrogenated La(Fe-Mn-Si)13-H with Mn substituting Fe to finely tune the transition temperature. We measured the specific heat under magnetic field cp(H, T) and the magnetic field induced isothermal entropy change Δs(H, T) of a series of compounds by direct Peltier calorimetry. Results show that increasing Mn from 0.06 to 0.46 reduces the transition temperature from 339K to 270K whilst the total entropy change due to a 1.5 T field is depressed from 18.7 J kg-1K-1 to 10.2 J kg-1K-1 and the thermal hysteresis similarly is reduced from 1.5K to zero. In the paper, we interpret the results in terms of a magnetic phase transition changing from the first to the second order with increasing Mn content, and we discuss the value of the results for magnetic cooling applications. [ABSTRACT FROM AUTHOR]

The gas phase emitter effect increases the lamp lifetime by lowering the work function and, with it, the temperature of the tungsten electrodes of metal halide lamps especially for lamps in ceramic vessels due to their high rare earth pressures. It is generated by a monolayer on the electrode surface of electropositive atoms of certain emitter elements, which are inserted into the lamp bulb by metal iodide salts. They are vaporized, dissociated, ionized, and deposited by an emitter ion current onto the electrode surface within the cathodic phase of lamp operation with a switched-dc or ac-current. The gas phase emitter effect of La and the influence of Na on the emitter effect of La are studied by spatially and phase-resolved pyrometric measurements of the electrode tip temperature, La atom, and ion densities by optical emission spectroscopy as well as optical broadband absorption spectroscopy and arc attachment images by short time photography. An addition of Na to the lamp filling increases the La vapor pressure within the lamp considerably, resulting in an improved gas phase emitter effect of La. Furthermore, the La vapor pressure is raised by a heating of the cold spot. In this way, conditions depending on the La vapor pressure and operating frequency are identified, at which the temperature of the electrodes becomes a minimum. [ABSTRACT FROM AUTHOR]

Perovskite-structured Ba1-xLaxSnO3 (x=0-0.10) films have been directly grown on (0001) sapphire substrates by a sol-gel method. Optical properties and bandgap energy of the films have been investigated by transmittance spectra from 10K to 450 K. It indicates that these films exhibit a high transmission of more than 80% in the visible region. With increasing temperature, there is a significant bandgap shrinkage of about 0.5 eV for lightly La doping (x⩽0.04) films. For heavily La doping concentration (x⩾0.06), the bandgap remains nearly stable with the temperature and La composition. This is due to the fact that the lattice expansion caused by La doping is close to the saturation for the film doped with x=0.06. Moreover, temperature dependent conductivity behavior shows a similar pattern, which suggests that the doping concentration of La-doped BaSnO3 (BLSO) films has a saturated state. The La introduction can modify the Sn 5s-O 2p antibonding state and the nonbonding O 2p orbital, which remarkably affect the electronic bandgap of the BLSO films. [ABSTRACT FROM AUTHOR]

Magnetotransport properties of La2/3Sr1/3MnO3/LaAlO3/Pt tunnel junctions have been thoroughly analyzed, as a function of temperature and magnetic field, to test the suitability of LaAlO3 for insulating barriers and spin injection processes. The insulating behavior of LaAlO3 maintained down to 1-2nm (corresponding to 4-5 unit cells) renders this material useful as tunnel barrier. The temperature dependence of the junction resistance, R(T), down to 200K confirms direct tunneling as the dominant conduction channel. The barrier parameters of the junctions, φ0 and s, are estimated using Simmons' model in the intermediate voltage range. The energy of the barrier was estimated to be φ0~0.4V at room temperature. The dependence of R(T) and φ0 on the magnetic field shows an anisotropic tunneling magnetoresistance of ~4% at low T when changing the direction of the magnetization with respect to the current flow. [ABSTRACT FROM AUTHOR]

In this study, La0.8Pb0.1Ca0.1Fe1−xCoxO3 (x = 0.10 and x = 0.20) thin films with respective thicknesses of 300 and 600 nm have been prepared by the drop coating technique onto a Si/SiO2 substrate with platinum interdigitated electrodes. The effects of cobalt-content and film thickness on the ozone sensing properties have been studied. The sensor responses have been determined in an operating temperature range between 160 and 280 °C. Sensors have been exposed to different concentrations between 50 and 400 ppb of ozone gas at a constant flow rate of 500 ml min−1 dry air. The studied La0.8Pb0.1Ca0.1Fe1−xCoxO3 (x = 0.10 and x = 0.20) compounds could be a promising sensitive film for ozone detection, especially for the thinnest sensitive layer, 300 nm in our case. [ABSTRACT FROM AUTHOR]

The effect of La2O3 and Y2O3 additions on the improvement of regenerated cemented carbide properties was investigated. The WC-Co powder recycled by the zinc melting method was used as a raw material, and five alloys were prepared by conventional powder metallurgy process by adding La2O3 and Y2O3 with 0, 0.3, and 0.6 wt.%, separately. The results show that they have a certain effect on the carbide compactness, but it is not obvious. When the La2O3 or Y2O3 content is less than 0.3 wt%, the hardness of regenerated cemented carbide will be slightly increased and then significantly decreased. A rare-earth oxide exhibits significant improvement of fracture toughness and transverse rupture strength, and the performance of carbide with Y2O3 is better than that with La2O3. When 0.3 wt.% Y2O3 is added, integrated mechanical properties of regenerated cemented carbide are excellent: hardness is 1720 HV30 kgf, fracture toughness is 8.41 MPa ·m1/2, and rupture strength is 1653 MPa. [ABSTRACT FROM AUTHOR]

In this study, the lanthanum sulfide-manganese sulfide (La2S3-MnS) nanosheet composite films with different thicknesses were grown on graphene oxide (GO) (LMS/GO) coated stainless steel substrate using binder-free successive ionic layer adsorption and reaction (SILAR) method, for the first time. The formation of crystal structure and chemical states was identified using X-ray diffraction analysis and X-ray photoelectron spectroscopy, respectively. The nitrogen sorption analysis showed the micro-/mesoporous structure of La2S3-MnS-90/GO thin film exhibiting a specific surface area of 170 m2 g-1 and hydrophilic nature. The scanning electron microscopic image showed microstructure with porous ultrathin interconnected nanosheets. Surface texture was examined using transmission electron microscopy. The resulting La2S3-MnS-90/GO thin film electrocatalyst showed oxygen evolution reaction (OER) overpotential as low at 263 mV to reach 10 mA cm-2 current density with Tafel slope of 48 mV dec-1 for in 1 M KOH solution and stability over 50 h. Consequently, it could be considered one of the alternate sulfide-based catalysts for highly efficient OER evolution. [ABSTRACT FROM AUTHOR]

In this study, polymeric films based on chitosan (CS) doped with Lanthanum oxide nanoparticles at different weight percentages (5, 10, 15, and 20% La2O3/CS) were prepared using the simple solution cast transformation. The dielectric constant increases with increasing the La2O3 content, and this could be attributed to the induced defects, as a result more dipoles are produced in the polymer matrix. Also, the values of Z′ and Z″ increase with La contents. On other hand, we noticed that the plot of the normalized-imaginary electric modulus versus the frequency shows a clear peak at high frequency for all samples. This peak is associated with ionic conduction. The AC conductivity increased by increasing the La2O3 content. Furthermore, AC conductivity increases with frequency because the absorbed energy from the electric field can increase the number of charge carriers that are participating in the electric conduction. Moreover, the values of the universal exponents were larger than the unity and increase with increasing temperatures which means that the conduction process may be pertinent to reorientational (or localized) mechanism. [ABSTRACT FROM AUTHOR]