Lanthanum Aluminate Research Articles

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.

Facile synthesis of perovskite lanthanum aluminate and its green reduced graphene oxide composite for high performance supercapacitors

A facile simple hydrothermal synthetic route has been developed for the synthesis of perovskite lanthanum aluminate (LaAlO3) and reduced graphene oxide composite (RGO). Green tea extract here is used as reducing agent for conversion of graphene oxide to reduced graphene oxide. The synthesized materials have been characterized for its morphology using, XRD, SEM, EDAX, FTIR and BET techniques. The materials are used as electrode materials for supercapacitor applications. Electron microscopic images indicate RGO sheets are densely attached to surface of LaAlO3 with perforated cage like morphology. A high specific capacitance of 721 F g−1 at a scan rate of 2 mV s−1 was exhibited by RGO/LaAlO3 hybrid structure electrode when compared to pure RGO (531 F g−1) and pure LaAlO3 (105 F g−1) electrodes at the same scan rate using cyclic voltammetry (CV). By using chronopotentiometry (CP), the RGO/LaAlO3 hybrid structure electrode out stretched specific capacitance of 283 F g−1 at a current density of 0.5 A g−1 and able to retain specific capacitance (Csp) of about 157 F g−1 even at very high current density of 20 A g−1. RGO/LaAlO3 composite also possesses an energy density of 57 Wh kg−1 with a maximum power density of 569 W kg−1. RGO/LaAlO3 nanocomposite has also been fabricated for asymmetric supercapacitor device (ASD) system. From the Electrochemical Impedance Spectroscopy (EIS), the RGO/LaAlO3 hybrid structure electrode has shown phase angle close to −90° for frequency up to 0.01 Hz, suggesting that the nanocomposite electrode material approached ideal capacitor behaviour.

Fast adsorptive removal of direct blue-53 dye on rare-earth doped Lanthanum aluminate nanoparticles: equilibrium and kinetic studies

The nanocrystalline LaAlO3: Sm3+: Bi3+ composites are synthesized using sugar as fuel through the solution combustion process. Prepared composites were well categorized by Powder Xray Diffraction (PXRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), UV- Visible spectroscopy, Fourier Infrared Transform (FTIR) spectroscopy, Brunauer-Emmett-Teller (BET) analysis. The average size of the crystallites as estimated using Scherrer equation is in the range 30–46 nm agreeing with TEM results. The SEM images show the spherical agglomerated nanoparticles. The nominal composition of dopant and co-dopant ions present inside the host lattice is confirmed with EDX patterns. The adsorption of Direct Blue-53 (DB-53) dye has been investigated. The influence of adsorbent load, the concentration of dye, pH and time on adsorption of Direct Blue-53 dye was studied. The statistical error computation and nonlinear curve fitting of experimental isotherm and kinetic data are carried out using Excel solver-2019 (Microsoft office-2019 USA). The kinetic studies indicate that the adsorption process follows pseudo first-order kinetics and isotherm studies suggest that the Dubinin-Radushkevich (D-R) isotherm model is well fitted and is in good agreement with experimental data. The adsorbent is admirable and promising in the adsorption capacity and is beneficial in the elimination of toxic and non-biodegradable organic pollutants in water.

Extraordinary quasi-two-dimensional magnetotransport properties of a LaAlO3/SrTiO3 heterostructure tailored with a surface TiO2 atomic sheet

Epitaxial heterostructures of lanthanum aluminate (LaAlO3) and strontium titanate (SrTiO3) exhibit extraordinary quasi-two-dimensional magnetotransport properties at low temperatures. To elucidate the mechanisms responsible for the unique properties of these interfaces, which can guide the design of novel structures having high performances, extensive analyses of the magnetotransport properties at low temperatures are required. We report the magnetotransport properties of a LaAlO3/SrTiO3 system tailored with a topmost surface atomic sheet of titanium dioxide (TiO2). Three unit cells of LaAlO3 were deposited on a reconstructed SrTiO3(001)-(13×13)-R33.7° substrate, yielding LaAlO3 covered with a single-atom-thick TiO2 sheet. The high-mobility electrons confined at the LaAlO3/SrTiO3 interface provided significantly high magnetoresistance ratios of +150% and −80% under magnetic fields perpendicular and parallel to the interface, respectively. The in-plane anisotropic magnetoresistance at 4.2 K reached approximately +30%, reflecting the Rashba spin–orbit interactions of the quasi-two-dimensional electrons. A high carrier concentration at the interface realized by the capping of LaAlO3/SrTiO3 with the surface TiO2 sheet significantly contributed to the enhancement of magnetotransport properties arising from the Ti 3d orbitals.

Effect of low-k oxide thickness variation on gate-all-around floating gate with optimized SiO2/La2O3 tunnel barrier

This paper reports the use of a novel lanthanum oxide (La2O3) tunnel barrier layer with low-k materials, silicon dioxide (SiO2) to improve Gate-All-Around Floating Gate (GAA-FG) memory performance performed using 3-Dimensional (3D) simulator of Silvaco ATLAS. We examine the ability of Variable Oxide Thickness (VARIOT) concept for several high-k dielectric materials using lanthanum oxide, yttrium (III) oxide, aluminum oxide, zirconium dioxide and hafnium (IV) oxide (La2O3, Y2O3, Al2O3, ZrO2 and HfO2) to evaluate the memory characteristics including tunneling current, program/erase (P/E) operation and memory window. In this work, low-k oxide thickness, SiO2 is varied at 1:1:4 nm. Importantly, this finding shows that the combination of SiO2/La2O3 asymmetric stack have distinct consequences at the lowest programming voltage with Vprog = 4.7 V. In addition, the ability of silicon dioxide / lanthanum oxide (SiO2/La2O3) tunnel stack is significantly improved when the low-k oxide thickness, SiO2 is reduced. The proposed thickness ratio of SiO2 on GAA-FG memory cell yields substantial increased in memory window from 0.04 V to 5.0 V at the same P/E time, t = 0.1 ms. The optimized SiO2/La2O3 combination in this study demonstrated potentials flash memory architecture in the future.

Stopping power and inelastic mean free path of 300 eV–50 keV electrons for lanthanum aluminate

SP (Stopping Power) and IMFP (Inelastic Mean Free Path) of lanthanum alumínate (La2O3)x (Al2O3)1–x was varied with x = 0.25, 0.34, and 0.5. for electron energy from 300 eV to 50 keV have been determined by using composite Simpson from the equation of Born Ochkur correction. The main parameter in determining the SP and IMFP is Energy Loss Function (ELF) which was obtained from the experimental reflection electron energy loss (REELS) spectra. The method in this study is convenient methods for determining SP for binary compound lanthanum aluminate.

Spatial beam self-cleaning in multimode lanthanum aluminum silicate glass fiber

We demonstrated that spatial Kerr beam self-cleaning can be obtained in a highly multimode multicomponent optical fiber based on lanthanum aluminum silicate oxide glasses (SiO2-Al2O3-La2O3), which was made by using the modified powder in tube technology (MIPT). We show how such fabrication method can provide interesting potentialities to design doped multimode optical fibers with homogeneous and quasi-parabolic refractive-index core profile for nonlinear optics applications.

Substrate strain and doping effects on the crystal structure of SrNbxTi1−xO3

Strontium titanate, SrTiO3 (STO), is an interesting material for both fundamental studies and technological applications. Modifications of the atomic and crystal structure by doping, e.g. replacing titanium with niobium atoms, and by strain, i.e. by growing STO on a different substrate such as lanthanum aluminate, LaAlO3 (LAO), have been proposed to tune the STO electronic, optical and transport properties for applications. Here we report the results of ab initio density-functional theory (DFT) simulations of both strain and Nb-doping effects, independently and joint, on the STO crystal structure. We found that the DFT energy differences among the three commonly observed STO crystal structures, Pm3m, P4∕mmm, and I4∕mcm, are very small, <2.6 × 10−4 Ry, so that the ground-state cannot be determined unambiguously at this level of theory and physics. Our calculations show that an in-plane strain, at least at the level of only − 0.4% as observed in STO on LAO, does not lead to the expected increase in c toward tetragonal symmetry, where c is the length of the cell axis perpendicular to the plane. Instead, c also is reduced and the cubic symmetry tends to be restored. Nb doping, even at the maximum experimental level of 3.7%, does not have significant effects on lattice parameters. The latter result is confirmed also under the presence of strain, so we could not find any crossed effect of strain and doping.

Nanostructural and Electrical Properties of Al/Sn/La2O3 Nanocomposite as a Gate Dielectric of MOSFETs

Metal–oxide–semiconductor field-effect transistors (MOSFETs) have significant role on producing the electronic devices. The producers try to make the chips in smaller size so they need materials with high dielectric constant. Here, in this research, Al/Sn/La2O3 will introduce as a material with higher dielectric constant and less defections. In this research, Al/Sn/La2O3 nanostructure was prepared by sol–gel and spin-coating methods. Lanthanum chloride (LaCl3·7H2O), cetyltrimethylammonium bromide, ammonia (25%), aluminum tri-sec-butylate (C12H27AlO3), acetyl acetone (C2H5O8), isopropyl alcohol (C3H8O), Tin (II) chloride (SnCl2) and H2O were used to synthesize Al/Sn/La2O3. Structural properties and surface morphology of nanocrystallites were investigated by X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, atomic force microscopy and Fourier-transform infrared radiation, respectively. Electrical properties were determined with metal–dielectric–semiconductor through capacitance–voltage (C–V), the hysteresis curve and current density–voltage (J–V). The conduction mechanism was measured in the temperature range of 330 K < T < 410 K and in the electrical field < 0.12 MV cm−1, and the results showed ohmic emission. A thermal excited model was proposed to explain the mechanism of ohmic conduction current. The highest value of dielectric constant (k) for Al/Sn/La2O3 structure was 33 at T = 250 °C with almost amorphous structure. The result showed that $$ \frac{{I_{\text{on}} }}{{I_{\text{off}} }} $$ of Al/Sn/La2O3 structure was ~ 1.3. The leakage current and capacitance–voltage of Al/Sn/La2O3 nanocomposite for the sample calcined at T = 250 °C showed that this sample can be good enough for using as a gate dielectric of MOSFETs.

Thermal and structural analysis of 40La2O3-10Nb2O5-(50-x)Al2O3-xBaO glasses

Aluminate glasses have excellent optical and mechanical properties, in addition to high thermal and chemical stability. However, aluminate glasses require high melting temperatures and exhibit poor glass forming ability, causing difficulties while preparation by the melt-quench method. Therefore, it is necessary to establish novel methods to improve melting conditions and glass forming tendencies for aluminate glasses. 40La2O3-10Nb2O5-(50-x)Al2O3-xBaO (x = 0, 2.5, 5, 7.5, 10) glasses were prepared by the aerodynamic levitation method. XRD, DTA, and Raman and NMR spectroscopic techniques were used to investigate the effects of BaO on the structure and thermal properties—including crystallization behavior—of lanthanum aluminate glass. The results show that the addition of BaO increases the glass transition temperature (Tg) and stability ΔT of the baseline glass, as Al-Ba-7.5 (40Al2O3-10Nb2O5–42.5Al2O3–7.5BaO) glass has the highest ΔT value (151 °C). The 27Al MAS NMR spectrum of a high BaO-content glass (Al-Ba-10) shows that about 80% of [IV]Al and 15% of [V]Al are present in the glass network. Raman scattering spectra indicate that a peak shown around 790 cm−1canbe assigned to the internal stretching vibrations of the Al-non-bridging oxygen (NBO) bonds in depolymerized [AlO4/2] tetrahedrons. The crystallization activation energies were calculated to be 1157.1 kJ/mol and 891.7 kJ/mol (Kissinger method) for Al-Ba-x (x = 0, 7.5) glasses, respectively, which progresses as a diffusion-controlled three-dimensional growth process. The nucleation rate of Al-Ba-0 decreases continuously, while Al-Ba-7.5 increases.

Multifunctional macroporous solid oxide fuel cell anode with active nanosized ceramic electrocatalyst

In this work, an alternative anode material, consisting of perovskite-type manganese-doped lanthanum aluminate (La1.5Al0.33Mn0.17O3), was proposed and implemented. The solid oxide fuel cell anode was produced by the wet impregnation of nanoparticles into a macroporous electrolyte-based scaffold material. The produced cell was characterized by X-ray diffraction and scanning electron microscopy, from which the morphology of the scaffold, the particle size distribution, and porosity were extensively performed and discussed. Electrochemical and electrocatalytic tests were accounted by recording i-V plots with hydrogen or methane as fuels, and by measuring methane conversion rates and C2 hydrocarbons selectivity.The particle size distribution was confirmed to be submicrometric with the presence of nanoparticles. High levels of porosity (30–35%) were achieved at the scaffold and the cells were able to operate with hydrogen and methane as fuels delivering a power density of around 150 mW.cm−2 and yielding 30–70% C2 hydrocarbons selectivity, depending on operational conditions.

Exchange Interactions between Atoms of Rare-Earth Elements in the Perovskite Structure

Solid solutions of lanthanum aluminates containing rare-earth elements (cerium, europium, gadolinium, and ytterbium), were studied by the magnetic dilution method. Exchange interactions between lanthanide atoms in the perovskite structure were found.

Perovskite lanthanum aluminate nanoparticles applications in antimicrobial activity, adsorptive removal of Direct Blue 53 dye and fluoride

In the present study, efficient adsorptive removal of fluoride and Direct Blue 53 (DB-53) dye solution on perovskite lanthanum aluminate (PLA) has been investigated. To characterize the prepared PLA with analytical techniques like FTIR, SEM, EDS, PXRD, PHZPC and BET. The influence of adsorbent dose (0.05–0.6) gL−1, pH (2−12), contact time (0–60 min) and initial adsorbate concentration (0–50 mg L−1) were studied on adsorption process. Mathematical modeling of kinetics and isotherms were computed using equations. The pseudo-second-order kinetic and Halsey isotherm equilibrium model are best fitted with experimentally computed data with R2 > 0.96. The value of free mean energy EDR per adsorbate molecule was 1.77 kJmol−1 (fluoride) and 1.86 kJmol−1 (DB-53) with an adsorption capacity 25.103 and 38.03 respectively, hence nature of adsorption suggested as physisorption process. The maximum Langmuir adsorption capacity of PLA was investigated to be 40.8 mgg−1 (fluoride) and 71.4 mgg−1 (DB-53). Present study PLA deficits efficient adsorbent for fluoride and DB-53 dye for ground and industrial wastewater. Further, the effect of in-vitro antimicrobial studies was carried out against six test microorganisms. PLA showed, a maximum antibacterial effect at MIC 63 μg mL−1 for Gram-negative bacteria: Pseudomonas aeruginosa (NCIM 5029) due to the interaction between the positively charged nanoparticle and negatively charged cell wall.

A development of new red phosphor based on europium doped as well as substituted Barium Lanthanum Aluminate (BaLaAlO4: Eu3+)

New red emitting Eu3+ doped and substituted BaLaAlO4 phosphor powders were synthesized by simple modified solid state reaction method. BaLaAlO4 crystal phase formation studied through powder X-ray diffraction (XRD) analysis. Fourier Transform - Infra Red (FT-IR) analysis was performed to study the formation of the host with respect to temperature increment and metal-oxygen bond vibrations of BaLaAlO4 host lattice. Morphology of the phosphor was appeared as irregular in shapes with agglomeration. Photoluminescence (PL) analysis was performed to study the PL excitation and emission characteristics of the phosphor. It dictates that synthesized phosphors exhibited a strong red emission at 626 nm. Substitution effect of Eu3+ in BaLaAlO4 with various compositions such as Ba(1-x)LaAlO4: Eux3+, BaLa(1-y)AlO4: Euy3+ and BaLaAl(1-z)O4: Euz3+ were studied for PL enhancement. Luminescence decay time of the phosphors was also determined. PL thermal quenching and Commission Internationale de l'Eclairage (CIE) chromaticity analysis were carried out to find thermal stability and colour purity of the phosphor sample respectively. The Judd- Ofelt parameters (Ω2 & Ω4) obtained from the emission spectra of Eu3+ ions in BaLaAlO4 host lattice were evaluated and discussed.

Thermoluminescent properties of LaAlO3:C crystals synthesized by solid state reaction applied to UV Dosimetry

In this work, the thermoluminescent (TL) response of carbon doped lanthanum aluminate crystals grown by solid state reaction method was investigated. Three syntheses using different combinations of Al2O3, La2O3 and 0.1 wt % of carbon atoms were conducted. The 1:1 mixture of aluminum and lanthanum oxide was mixed with 0.1wt.% carbon and annealed at 1700°C for two hours in a hydrogen atmosphere. The X-ray diffraction analysis revealed the formation of the rhombohedral LaAlO3 crystallographic phase. Ultraviolet-visible spectroscopies were obtained and F and F+ centers were identified ascribed. Fourier transform infrared spectroscopic data show higher and lower frequencies assigned to AlO6 octahedra in LaAlO3. The UV irradiations were carried out using a commercial 8W UV lamp. Thermoluminescence measurements were performed at a Harshaw 4500 TL reader. The three syntheses were very efficient to obtain carbon doped LaAlO3 crystals with high thermoluminescent output, for low exposure rates of UVR fields.

Thermoluminescent properties of LaAlO3:C crystals synthesized by solid state reaction applied to UV Dosimetry

In this work we have investigated the thermoluminescent (TL) response of carbon doped lanthanum aluminate crystals grown by solid state reaction method. We conducted three syntheses by different combinations of Al2O3, La2O3 and 0.1 wt % of carbon atoms. The 1:1 mixture of aluminum and lanthanum oxide was mixed with 0.1wt.% carbon and annealed at 1700°C for two hours in a hydrogen atmosphere. The X-ray diffraction analysis revealed the formation of the rhombohedral LaAlO3 crystallographic phase. F and F + centers were identified by ultraviolet-visible spectroscopy. Fourier transform infrared spectroscopic data show higher and lower frequencies assigned to AlO6 octahedra in LaAlO3. The UV irradiations were carried out using a commercial 8W UV lamp. Thermoluminescence measurements were performed at a Harshaw 4500 TL reader. The three syntheses were very efficient to obtain carbon doped LaAlO3 crystals with high thermoluminescent output, for low exposure rates of UVR fields.

Theoretical Study of Phonon Dispersion of Lanthanum Aluminate in Terahertz Frequency

The phonon dispersion spectrum, eigenvector and lattice vibration frequency of cubic crystalline lanthanum aluminate (LaAlO3) are studied by density functional theory (DFT). The effects of lattice constant, K-point selection and kinetic-energy cutoff (Ecut) on the calculation accuracy are discussed. The vertical parallel relationship between the phonon propagating wave vector and the atomic vibration direction is analyzed to obtain the frequency of the LaAlO3 transverse (TO)/longitudinal (LO) optical phonon. The comparison results of the first-principles calculation software Materials Studio, the open source component package ABINIT, and he open source component package Quantum Espresso show that the calculation accuracy depends on the convergence analysis and the approximation method adopted in the calculation process.

Electrical conductivity and infrared ray photoconductivity for lattice distorted SmNiO&lt;sub&gt;3&lt;/sub&gt; perovskite oxide film

The metal-to-insulator transitions achieved in rare-earth nickelate (&lt;i&gt;R&lt;/i&gt;NiO&lt;sub&gt;3&lt;/sub&gt;) receive considerable attentions owning to their potential applications in areas such as temperature sensors, non-volatile memory devices, electronic switches, etc. In contrast to conventional semiconductors, the &lt;i&gt;R&lt;/i&gt;NiO&lt;sub&gt;3&lt;/sub&gt; is a typical electron correlation system, in which the electronic band structure is dominant by the Coulomb energy relating to the &lt;i&gt;d&lt;/i&gt;-band and its hybridized orbitals. It was previously pointed out that lattice distortion can largely influence the electronic band structures and further significantly affect the electronic transportation properties, such as the resistivity and metal-to-insulator transition properties. Apart from directly measuring the transportation performance, the variations in the origin of carrier conduction and orbital transitions relating to the strain distortion of &lt;i&gt;R&lt;/i&gt;NiO&lt;sub&gt;3&lt;/sub&gt; can also be reflected via their optical properties. In this work, we investigate the optical properties of samarium nickel (SmNiO&lt;sub&gt;3&lt;/sub&gt;) thin films when lattice distortions are induced by interfacial strains. To introduce the interfacial strain, the SmNiO&lt;sub&gt;3&lt;/sub&gt; thin films are epitaxially grown on the strontium titanate (SrTiO&lt;sub&gt;3&lt;/sub&gt;) and lanthanum aluminate (LaAlO&lt;sub&gt;3&lt;/sub&gt;) single crystal substrates by using the pulsed laser deposition. A bi-axial tensile distortion happens when the SmNiO&lt;sub&gt;3&lt;/sub&gt; thin films are grown on SrTiO&lt;sub&gt;3&lt;/sub&gt; due to the smaller lattice constant of SmNiO&lt;sub&gt;3&lt;/sub&gt; than that of SrTiO&lt;sub&gt;3&lt;/sub&gt;, while the one grown on LaAlO&lt;sub&gt;3&lt;/sub&gt; is strain-relaxed. We measure the infrared radiation (IR) transmission spectra of the SmNiO&lt;sub&gt;3&lt;/sub&gt; thin films grown on various substrates. The obtained IR transmission spectra are fitted by a Drude-Lorentz model and further converted into the curves of photoconductivity versus IR frequency. Comparing the difference in photoconductance between low frequency and high frequency reflects the two different origins of the conduction, which are related to intraband transition and band-to-band transition, respectively. The smaller photoconductance is observed for SmNiO&lt;sub&gt;3&lt;/sub&gt;/SrTiO&lt;sub&gt;3&lt;/sub&gt; than for SmNiO&lt;sub&gt;3&lt;/sub&gt;/LaAlO&lt;sub&gt;3&lt;/sub&gt; at low frequency, and this is expected to be caused by the suppression of free carriers as reported previously for tensile distorted SmNiO&lt;sub&gt;3&lt;/sub&gt;. The consistence is obtained when further measuring the electronic transportation such as temperature-dependent electrical resistivity, as a higher resistivity is observed for SmNiO&lt;sub&gt;3&lt;/sub&gt;/SrTiO&lt;sub&gt;3&lt;/sub&gt; than for SmNiO&lt;sub&gt;3&lt;/sub&gt;/LaAlO&lt;sub&gt;3&lt;/sub&gt;. The combination of the investigation of electrical transport with that of infrared transmission indicates that the tensile distortion in structure stabilizes the insulating phase to eliminate a pronounced metal-to-insulator transition and elevates the transition temperature. This is related to the respective twisting of the NiO&lt;sub&gt;6&lt;/sub&gt; octahedron when tensile distortion regulates the valance state of the transition metal and further opens the band gap, which is further confirmed by results of the X-ray absorption spectrum.

Optical spectroscopy of Rh3+ ions in the lanthanum-aluminum oxide systems

A series of the Rh-containing samples supported on pure γ-Al2O3, La-doped γ-Al2O3, LaAl11O18 and LaAlO3 was prepared and characterized. Diffusion of Rh3+ ions from the surface of the support into its bulk causing the rapid deactivation of the catalyst in a model reaction of CO oxidation under the prompt thermal aging conditions was shown to be accelerated by a presence of lanthanum. The amount of rhodium disappeared from the surface during the high temperature treatment was estimated by a testing reaction of ethane hydrogenolysis and an electron paramagnetic resonance spectroscopy with spin probe. In order to characterize rhodium ions diffused into the bulk of the support at different calcination temperatures, the optical spectroscopic methods (diffuse reflectance UV–vis and photoluminescence spectroscopies) were applied. Rh3+ ions were shown to be applicable as a luminescence probe to follow the process of their bulk diffusion and localization within the matrix of the support, as well as for the structure identification of the La-containing sites responsible for the alumina thermal stabilization. The obtained data on luminescence of Rh3+ ions indicate that already at 800 °C the oxygen octahedrons corresponding to LaAl11O18 structure are being formed in the local coordination surroundings of isolated La ion in the 4%La2O3-Al2O3 support. It is important to notice that the structures of such kind can be formed in La-doped aluminas only. There are no octahedron positions with sufficient values of the crystal field for the formation of luminescence centers of Rh3+ ions in pure γ-Al2O3.

RE3+:LaALO3 doped luminescent polymer composites

In this work we summarize the results of our research on design and development of the PMMA-based composites doped with lanthanum aluminum oxide (LaAlO3) nanocrystals activated with selected rare-earth ions - dysprosium, holmium, thulium and praseodymium. A set of rare-earth doped nanopowders, differing in activators' concentration was manufactured and carefully characterized with respect of luminescent properties in the visible spectral range. The samples of optimal luminescent features were introduced into PMMA polymer, constituting the luminescent composite materials with the active centers shielded from the parasitic interactions with polymer phonons. These, in turn, were subjected to optical characterization covering luminescence spectra and kinetics measurements, which enabled comparison of the luminescent features and assessment of the quality of developed materials as well as correctness of proposed approach.