Lanthanum Aluminate Research Articles

Visible and Near-Infrared emission properties of Yb3+/Pr3+ co-doped lanthanum aluminum silicate glass

Yb3+/Pr3+ co-doped lanthanum aluminum silicate glasses (Yb3+/Pr3+-SAL glass) are prepared by high temperature melting process. The optical properties of Yb3+/Pr3+ co-doped lanthanum aluminum silicate glasses are studied. The result shows that Yb3+/Pr3+ co-doped lanthanum aluminum silicate glasses have intense absorption range from 440 to 500nm. In addition, the intense emission band centered at 620nm and 607nm are observed with the excitation of 488nm in different doping concentration. These results demonstrate that Yb3+/Pr3+ co-doped lanthanum aluminum silicate glasses can be used as a potential material for visible laser and near-infrared broadband fiber amplifiers.

A terahertz Brewster switch based on superconductor hyperbolic metamaterial

Active polarization switching devices are important to control the polarization state of light including terahertz (THz) waves that are technologically challenging to manipulate. Here, we propose and numerically demonstrate a hyperbolic metamaterial-based (HMM-based) active Brewster polarization switch for the intensity and phase modulation of THz light. The proposed multilayered HMM consists of alternating thin layers of high temperature superconductors such as yttrium barium copper oxide and dielectric materials such as lanthanum aluminate. The HMM shows elliptical dispersion above the superconducting phase transition temperature and type II hyperbolic dispersion in the superconducting state. By varying the temperature from the dielectric to the superconducting phase of the HMM, we demonstrate above 98% THz intensity modulation and 100% phase tunability (180°) at Brewster’s angle. The proposed HMM can work as an efficient reflective THz modulator by properly selecting the angle of incidence.

Crystalline phase evolution and thermal behavior of zirconia-lanthanum aluminate ceramics produced by surface modification.

The purpose of the present work was to investigate the effect doping with lanthanum aluminate on the phase assemblage and thermal behavior of zirconia ceramics for biomedical applications. Four compositions were prepared by a surface modification route of either conventional tetragonal zirconia (3Y-TZP) or high translucency cubic-based zirconia (5Y-PSZ) to reach a nominal composition of either 0.5 wt. % (3Y-0.5LAO and 5Y-0.5LAO) or 5 wt. % of lanthanum monoaluminate (3Y-5LAO and 5Y-5LAO). Undoped powders were used as controls. DTA and XRD analyses revealed that lanthanum dizirconate crystallized in the 934°C-936°C range, while lanthanum aluminate crystallized in the 1,056°C-1,063°C range in both types of zirconias doped at the 5% level. No second phase was found in compositions doped at the 0.5% level. The a lattice parameter and the amount of the cubic phase increased in both 3Y-5LAO and 5Y-5LAO. The microstructure of the compositions doped with 5% LAO was characterized by well distributed LAO twinned crystals and sparse needle-shaped lanthanum hexaaluminate crystals. A bimodal grain size distribution was observed in 5Y-doped compositions. This was attributed to abnormal grain growth of the cubic phase, and in line with aluminum segregation at grain boundaries and the presence of second-phase LAO crystals.

Adsorption of anionic dye on eco-friendly synthesised reduced graphene oxide anchored with lanthanum aluminate: Isotherms, kinetics and statistical error analysis

In the present study we made an effort to deploy eco-friendly synthesized reduced graphene oxide/Lanthanum Alluminate nanocomposites (RGO-LaAlO3) and Lanthanum Alluminate (LaAlO3) as adsorbents to remove dye from the synthetic media. XRD, SEM, BET surface area and EDX have been used to characterize the above-mentioned adsorbents. The impacts of different factors like adsorbent dosage, the concentration of adsorbate and PH on adsorption were studied. The best fit linear and nonlinear equations for the adsorption isotherms and kinetic models had been examined. The sum of the normalized errors and the coefficient of determination were used to determine the best fit model. The experimental data were more aptly fitted for nonlinear forms of isotherms and kinetic equations. Pseudo-second-order and Freundlich isotherm model fits the equilibrium data satisfactorily. Methyl orange (MO) has been used as model dye pollutant and maximum adsorption capacity was found to be 469.7 and 702.2 mg g−1 for LaAlO3 and RGO-LaAlO3, respectively.

Improving the performance of graphene nanoribbon field-effect transistors by using lanthanum aluminate as the gate dielectric

In nanoscale transistors, electron tunneling increases and causes a large leakage current due to the reduced channel length and gate oxide thickness. To reduce the short-channel effects and leakage current, the gate oxide can be selected from materials with high dielectric constant. In this paper, lanthanum aluminate (LaAlO3), a material with a high dielectric coefficient, is used as a gate dielectric in the structure of graphene nanoribbon field-effect transistors (GNRFET) and the effect of using this material on the device performance is studied. The transistor characteristics are extracted from device simulations performed by self-consistently solving the Poisson and Schrodinger equations in the nonequilibrium Green’s function formalism, employing the tight-binding approximation in the mode-space and ballistic regime. The ON-state and OFF-state currents, the ION/IOFF ratio, the threshold voltage, the drain-induced barrier lowering (DIBL), the subthreshold swing, and the transconductance (gm) are calculated for LaAlO3 as well as different materials as the gate dielectric to investigate the device performance. Based on the simulation results, the use of LaAlO3 as the gate dielectric in the transistor structure instead of other materials leads to larger values of the ON-state current, ION/IOFF ratio, and gm as well as smaller values of the OFF-state current, threshold voltage, DIBL, and subthreshold swing. According to the obtained results and excellent properties of LaAlO3, the use of this material could improve the performance of GNRFETs.

Optical emissions of chitosan modified LaAlO3: Bi3+, Tb3+ nanoparticles for bio labeling and drug delivery to breast cancer cells

Abstract Nanoparticles with luminescent properties have significant role in cancer theranostics and are extensively used as detection probes and drug carriers. Chitosan (CS) modified LaAlO3:Bi3+, Tb3+ nanophosphors (LNPs) is entrapped with anticancer agent capecitabine (CAP) for target imaging and drug delivery to breast cancer cells. LaAlO3: Bi3+, Tb3+ nanophosphors were synthesized by simple polyol mediated route and characterized by X-ray diffraction, Field emission scanning electron microscopy (FESEM), Energy Dispersive X-ray Analysis (EDAX), High Resolution Transmission Electron Microscopy (HRTEM) and fluorescence spectroscopy. Tb–Bi doped lanthanum aluminate nanoparticles show the typical green luminesce at 544 nm due to the energy transfer from Bi3+ to Tb3+ ions. Bismuth activated Lanthanum aluminate with terbium nanoparticles were then surface modified with CS to improve biocompatibility and facilitate entrapment of anticancer drug CAP. The drug delivery and imaging propensity of CS-CAP-LNPs was assessed in MDA-MB231 (breast cancer) cells. The obtained results demonstrated that CS-CAP-LNPs have greater cellular internalization and significant cytotoxicity (IC50 9 μg/ml) compared to naive LNPs. The CS-CAP-LNPs, therefore, is a promising multimodal system for therapy and bioimaging of breast cancer.

Thermal conductivity and compatibility of LaMgAl11O19/LaPO4 composites

As a toughening agent, LaPO4 has been used to improve several properties of ceramics. In such applications, its compatibility with the matrix material should be considered first. In this study, the compatibility of LaPO4 and magnesium lanthanum hexa-aluminate (LaMgAl11O19, LMA) was elucidated at temperatures ranging from room temperature to 1600 °C. The compositions, thermal stabilities, thermal conductivities and microstructures of the above-mentioned materials were analysed using X-ray diffraction, thermogravimetry-differential scanning calorimetry, thermal conductivity tester and scanning electron microscopy. The results indicated that the two materials maintained a good compatibility at temperatures lower than 1600 °C. At 1600 °C, the diffusion of La was observed to alter the chemical composition of LaPO4 and accelerate its reaction with LMA, leading to the formation of LaAlO3 and magnesium lanthanum aluminium oxide, resulting in the increase of thermal conductivity.

Synthesis and characterization of 50-50 wt. lanthanum aluminate-lanthanum zirconate composite dried by spray-drying

Lanthanum aluminate-lanthanum zirconate composite was synthesized by using coprecipitation and powders were dried by spray-drying. Pseudoboehmite was used as a precursor of lanthanum aluminate during the precipitation process. Highly crystalline phases were obtained. Lanthanum zirconate exhibits a pyrochlore structure at lower synthesis temperature (>1500°C). Due drying technique lanthanum aluminate particles appear surrounded by lanthanum zirconate. No other remaining phases were observed and the phase distribution in the composite was homogeneous.

Synthesis and characterization of nanomesoporous lanthanum aluminate (LaAlO3) for catalytic wet air oxidation of phenol

Nanomesoporous LaAlO3 synthesized by reverse microemulsion method were tested in the catalytic wet air oxidation (CWAO) of phenol in a fixed bed reactor. Synthesized LaAlO3 was characterized in depth by TG-DSC, XRD, FTIR, BET, TEM, TPD-CO2, TPD-NH3, and H2-TPR in order to relate its performances to the chemical and textural characteristics. Nanomesoporous LaAlO3 showed high activity towards phenol and in total organic carbon (TOC) removal with greater selectivity to non-organic compounds, a clear increase in the removal efficiency and selectivity relatively to non-catalytic wet air oxidation being observed. Effect of temperature, catalyst dosage, air flow, and phenol pumping rate in CWAO of phenol was investigated. LaAlO3 displayed high catalytic stability even after 6 h of continued reaction. Structural and textural stability of LaAlO3 was confirmed by XRD and BET surface area analysis of regenerated catalyst. Lewis basic sites and mesoporous nature of nano-LaAlO3 may play an important role in phenol degradation and TOC removal efficiency with high selectivity to non-organic compounds.

Optical enhancement of dielectric permittivity in reduced lanthanum aluminate

When light is absorbed in solids, electrical conductivity is usually enhanced through generation of photodoped conductive carriers, known as photoconduction. Here we show UV-light absorption restrains photoconduction, but markedly enhances dielectric permittivity in a ceramic sample of $\mathrm{LaAl}{\mathrm{O}}_{3}$ with defects introduced deliberately by reduction synthesis. Using systematic dielectric measurements under photoirradiation combined with computational studies for defect formation energies, we explain this unconventional photoinduced phenomenon in terms of photoexcited dipoles: The photoexcited electrons are trapped in in-gap states introduced by oxygen vacancies whereas photoexcited holes are localized in a valence-band maximum. Thus the created electron-hole pair acts as an electric dipole to enhance the dielectric permittivity. This unprecedented photoelectric effect does not only provide an alternative functionality for dielectric materials, but also paves the way for next-generation photoelectronic devices.

Ionic migrations during poling process in lanthanum aluminate investigated by time of flight-secondary ions mass spectrometry and piezoresponse force microscopy combined methodology

Time of flight-secondary ion mass spectrometry (ToF-SIMS) has been used to obtain the composition in depth of a few nanometers thick layer of lanthanum aluminate prepared by molecular beam epitaxy. The electrical properties of the films were probed by piezoresponse force microscopy (PFM) and Kelvin Force Microscopy (KFM). From PFM images, the sample under study behaves exactly as if it was ferroelectric although it is amorphous: this is a major artefact of this technique. This effect has often been related to the migration of oxygen vacancies within the sample, which modifies the molar volume under the AFM tip. ToF-SIMS results show that this effect may rather be due to the migration of lanthanum instead of oxygen vacancies. The authors also show that scanning with the tip of an atomic force microscope induces some chemical modifications at the surface. This combined methodology (ToF-SIMS, PFM, and KFM) allows one to better understand the contrast mechanisms at play during scanning probe experiments, especially when high electric fields and ionic migrations are involved.

Improved luminescence and LPG sensing properties of Sm3+-doped lanthanum aluminate thin films

Undoped and (1 mol%) Sm3+-doped LaAlO3 nanoparticles were synthesized by solution combustion technique utilizing sucrose as fuel. These rhombohedral perovskite nanoparticles thin films were prepared by spin coating on the ITO glass substrate. The XRD, SEM and TEM results show that the 40–60 nm crystallites are formed. The Photoluminescence Emission spectra and CIE coordinates show the enhancement of the yellowish orange color from Sm3+-doped LaAlO3 nanoparticles under the excitation wavelength of 406 nm. LPG detection was carried out for 0–1000 ppm concentrations. The sensor response of the Sm3+-doped LaAlO3 thin films was perceived to be > 87% for the detection of LPG through enhanced response as well as recovery time. Also, the stability analysis implied that the % sensor response remained favorably steady over a time period of 30 days. Owing to the improved % sensor response, quick response and recovery along with greater stability, these thin-film sensors showed better applications for detection of LPG leakage at room temperature.

Parameterization of dilute Ising model for iron-containing lanthanum gallate and aluminate solid solutions based on first-principles calculations

Calculations of the cubic models of two solid solutions LaGa0.5Fe0.5O3 and LaAl0.5Fe0.5O3 have been performed within the hybrid density functional theory. Multiple configurations have been considered for the solid solutions resulting from a different distribution of Fe atoms over the p-metal (Ga or Al) positions accounting for different spin orientation for Fe atoms themselves. It was demonstrated that 27 structures for both LaGa0.5Fe0.5O3 and LaAl0.5Fe0.5O3 should be treated to account for all the possible configurations in case of cubic 2 × 2 × 2 supercell. Optimized geometry, energy, and electron properties were calculated for all the obtained configurations. Statistical weights and probabilities were estimated for each symmetry non-equivalent configuration of the solid solutions within the canonical ensemble. A new parameterization for the dilute Ising model has been proposed. In this model, we account for non-magnetic contributions, which are absent in the simple Ising model, using the lattice approach based on the concept of interchange energy. Two model parameters (the magnetic coupling constant and interchange energy) were fitted to the calculated total energies of all considered configurations of both solid solutions. The dilute Ising model confirmed the benefit of Fe-clustering in doped lanthanum gallate against aluminate. Different signs of the estimated interchange energy enable us to explain the reasons for such differences.

Pascal conductance series in ballistic one-dimensional LaAlO3/SrTiO3 channels.

One-dimensional electronic systems can support exotic collective phases because of the enhanced role of electron correlations. We describe the experimental observation of a series of quantized conductance steps within strongly interacting electron waveguides formed at the lanthanum aluminate-strontium titanate (LaAlO3/SrTiO3) interface. The waveguide conductance follows a characteristic sequence within Pascal's triangle: (1, 3, 6, 10, 15, …) ⋅ e 2 /h, where e is the electron charge and h is the Planck constant. This behavior is consistent with the existence of a family of degenerate quantum liquids formed from bound states of n = 2, 3, 4, … electrons. Our experimental setup could provide a setting for solid-state analogs of a wide range of composite fermionic phases.

An unusual conductance sequence

Solid-State Physics Effects of correlations between electrons are enhanced in systems of reduced dimensions. The two-dimensional interface between two oxide materials, lanthanum aluminate (LaAlO3) and strontium titanate (SrTiO3), exhibits magnetism and superconductivity. In even lower-dimensional systems fabricated in similar heterostructures, electrons can pair without going superconducting. Briggeman et al. have now observed another exotic effect in LaAlO3/SrTiO3 waveguides: At certain magnetic fields, the conductance in these one-dimensional systems exhibits steps of an unconventional sequence. To understand the experimental data, the researchers used a model that accounted for interactions between electrons and found that the phenomenology was consistent with the formation of a series of correlated phases characterized by bound states of three or more electrons. Science , this issue p. [769][1] [1]: /lookup/doi/10.1126/science.aat6467

Enhanced humidity sensing performance of Samarium doped Lanthanum Aluminate at room temperature

In the present research, the enhanced room temperature operable humidity sensing response of lanthanum aluminate (LA) and (1 mol%) Sm3+ doped Lanthanum aluminate (SDLA) compound synthesized by solution combustion method using in-toxic and bio-degradable sucrose (C12H22O11) as fuel, is been discussed. Structural analysis are carried out by many analytical methods like X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier Transform infrared (FTIR) spectroscopy. The crystallite size for the compound is about 40−60 nm as depicted by XRD studies, the SEM images and BET studies show increased porosity and specific surface area correlated with the decreased crystallite size of SDLA compared to LA. Intensified agglomeration forming the greater pores available for sensing further confirmed by Transmission electron microscopy (TEM) images. The shifting in absorption bands at tetrahedral and octahedral sites is confirmed by FTIR spectra. SDLA has shown maximum sensing response of 92 % in the relative humidity (RH) range 11%–97%. The response time for the compound was found to be 40 s and 60 s and the stability was tested for 3 months. The mechanism of humidity sensing is schematically represented using various steps of adsorption processes.

Influence of Tb3+ doping on the structural and down-conversion luminescence behaviour of SrLaAlO4 nanophosphor

Different concentrations of terbium activated strontium lanthanum aluminates (SLA:Tb3+) were synthesized by adopting urea-aided solution combustion route at the sintering temperature of 1330 °C. XRD based Rietveld refinement technique confirms that SLA:Tb3+ nanophosphors have a perovskite-based structure with I4/mmm space group symmetry. Morphological information is collected on scanning and transmission electron microscopes (SEM & TEM) however, the energy dispersive mode of SEM (EDS) provides an idea about the distribution of existing elements throughout the host lattice. The band-gap studies for SrLaAlO4 (5.00 eV) and SrLa0.98Tb0.02AlO4 (4.50 eV) compositions are carried out using diffuse reflectance (DR) measurements via Kubelka-Munk relations. The down-converted photoluminescence (PL) studies reveal that an intense green emission is obtained at 545 nm due to 5D4 → 7F5 transition under 279 nm UV-excitation. Further, Dexter's theory helps in explaining the concentration quenching mechanism in SLA:xTb3+ nanocrystals (d-q interactions, s = 8.13). Moreover, the radiative lifetime (1.17 ms), non-radiative rates (194.28 s−1) and quantum efficiencies (81%) of 5D4 term are calculated using Auzel's model. Finally, the Commission International de I'Eclairage (CIE) color coordinates confirm the emission in green region; which approves the role of Tb3+-activated SLA nanophosphors as a green component in RGB based white light emitting diodes (WLEDs).

Arbitrary control of the diffusion potential between a plasmonic metal and a semiconductor by an angstrom-thick interface dipole layer.

Localized surface plasmon resonances (LSPRs) are gaining considerable attention due to the unique far-field and near-field optical properties and applications. Additionally, the Fermi energy, which is the chemical potential, of plasmonic nanoparticles is one of the key properties to control hot-electron and -hole transfer at the interface between plasmonic nanoparticles and a semiconductor. In this article, we tried to control the diffusion potential of the plasmonic system by manipulating the interface dipole. We fabricated solid-state photoelectric conversion devices in which gold nanoparticles (Au-NPs) are located between strontium titanate (SrTiO3) as an electron transfer material and nickel oxide (NiO) as a hole transport material. Lanthanum aluminate as an interface dipole layer was deposited on the atomic layer scale at the three-phase interface of Au-NPs, SrTiO3, and NiO, and the effect was investigated by photoelectric measurements. Importantly, the diffusion potential between the plasmonic metal and a semiconductor can be arbitrarily controlled by the averaged thickness and direction of the interface dipole layer. The insertion of an only one unit cell (uc) interface dipole layer, whose thickness was less than 0.5 nm, dramatically controlled the diffusion potential formed between the plasmonic nanoparticles and surrounding media. This is a new methodology to control the plasmonic potential without applying external stimuli, such as an applied potential or photoirradiation, and without changing the base materials. In particular, it is very beneficial for plasmonic devices in that the interface dipole has the ability not only to decrease but also to increase the open-circuit voltage on the order of several hundreds of millivolts.

Luminescence of alumina ceramic doped with lanthanum under medium- and high-dose irradiation

The synthesis of La-doped alumina ceramics results in a formation of new pulsed cathodoluminescence bands and thermoluminescence peaks which associated with phases of lanthanum aluminate (LaAlO3) and lanthanum aluminium oxide (LaAl11O18). Annealing at high temperatures (up to 1600 °C) with maximum lanthanum concentration allows to create ceramics with high intensity of 510 pulsed cathodoluminescence band and 370 K thermoluminescence peak. The high intensity of new peaks thermoluminescence demonstrates the material sensitivity to ionizing radiation and the possibility of its use as ionizing radiation detectors in the case of expanding the sublinear dose recording range.

A New Ag/AgBr/LaAlO3 Plasmonic Composite: Synthesis, Characterization, and Visible-Light Driven Photocatalytic Activity

In recent years, fabricating the visible-light induced photocatalysts based on the concept of plasmonic photocatalysis provides an efficient way to reduce environmental pollution. Accordingly, the present investigation has been carried out to develop such materials based on lanthanum aluminate (LaAlO3; LAO) and Ag/AgBr. The Ag/AgBr/LAO composite is prepared by deposition of metallic Ag nanoparticles onto the pre-prepared AgBr/LAO heterostructure by visible-light photo-reduction. The characteristic properties of synthesized catalysts were investigated by using a variety of techniques such as XRD, N2 adsorption–desorption, FESEM/EDX/EDS mapping, TEM-HRTEM, UV–Vis DRS, FT-IR, XPS, and PL measurements. The photocatalytic degradation of methylene blue (MB) was used as a probe reaction to evaluate their photocatalytic activity under visible-light irradiation. Because of the higher surface area with vast mesoporous nature, enhanced visible light absorption, and more efficient charge separation after the deposition of Ag/AgBr, the composite Ag/AgBr/LAO showed enhanced photocatalytic activity compared with pristine LAO. The recycling experiment revealed excellent stability (up to five successive cycles) of Ag/AgBr/LAO composite. Furthermore, a photocatalytic mechanism is proposed for the degradation of MB over Ag/AgBr/LAO composite. The composite Ag/AgBr/LAO can be used as a promising catalyst for environmental remediation.