La Zr Research Articles

One Pot Method to Synthesize a Novel La–Zr Composite with Exceptionally High Fluoride Removal Performance

A novel La–Zr composite was prepared by one pot method in mild conditions, and it shows a high fluoride removal ability of 143 mg/g. The powders were characterized by SEM, EDS, and FTIR. The effects of various factors such as pH, the presence of coexisting anions, contacting time, and initial fluoride concentration were investigated. The equilibrium data were studied by being fitted to several isotherm models, and the kinetic data are found to be described very well by the pseudo-second-order kinetic model. The overall rate of fluoride adsorption is likely to be controlled by chemisorption processes. The mechanism of adsorption was discussed in detail.

Carbon dioxide adsorption on lanthanum zirconate nanostructured coating surface: a DFT study

Pyrochlore lanthanum zirconate (La2Zr2O7) is a very promising candidate material for thermal barrier coating applications. However it may deteriorate by oxidizing gas such as CO2 during operating conditions. This paper investigates CO2 gas adsorption on La2Zr2O7 nanostructured coating surfaces using the density functional theory calculations. CO2 adsorption energies on (001), (011) and (111) planes in the La–Zr bridge positions have been calculated. The most favorable CO2 adsorption occurs on the (111) plane, which is confirmed by electron charge transfer and charge density difference analyses. La2Zr2O7 surface energies on (001), (011) and (111) planes have been calculated. Results show that (011) plane is the most thermodynamically stable plane due to its lowest surface energy.

Experimental and thermodynamic assessment of the La–Ti and La–Zr systems

The phase equilibria of the binary La–Ti and La–Zr system have been investigated between 900K and 2300K by combining conical nozzle levitation technique with in situ high energy synchrotron X-ray diffraction. The coexistence ranges of phases as well as experimental data of the liquidus and binodal line were obtained from the analysis of the diffraction data. The monotectic character of the La–Ti system is evident by the occurrence of two diffuse diffraction maxima according to the coexistence of two liquids above the monotectic temperature of 1845K±20K. The La–Zr phase diagram is a eutectic type, owning a metastable miscibility gap with a critical temperature close to the liquidus temperature. Based on the experimental data, thermodynamic descriptions of the La–Ti and La–Zr phase systems were derived.

Reduction of cobalt ion improved by lanthanum and zirconium as a triphenylphosphine stabilized nano catalyst for hydrolysis of sodium borohydride

La–Zr co-doped Co–B nanoparticle stabilized by Triphenylphosphine (TPP) is for the first time prepared in situ reduction by sodium borohydride at reflux condition. Obtained powders were characterized by XRD, BET, ICP, SEM–EDS and TEM techniques. TEM images depict that Co–B is appears formless and agglomerated powder. There are no agglomerated TPP stabilized La–Zr co-doped Co–B nanoparticles. It is concluded that, TPP as stabilizing agent can prevent agglomeration. TPP stabilized nanoparticle is formed as a spherical shaped particle. Particle size distribution is prepared and average size particle is about 13 nm. TPP stabilized La–Zr co-doped Co–B nanoparticle is highly active catalyst for hydrogen generation through the hydrolysis of sodium borohydride. It is also includes the full experimental details for the collection of a wealth of kinetic data to determine the activation energy (Ea = 45 kJ mol−1). Catalytic hydrolysis of NaBH4 is first order with respect to the catalyst concentration and also first order to the NaBH4 concentration in the case of TPP stabilized La–Zr co-doped Co–B nanoparticles.

Greener synthesis of propylene carbonate using graphene-inorganic nanocomposite catalysts

Continuous hydrothermal flow synthesis (CHFS) has been employed as rapid and cleaner route for the synthesis of a novel, highly efficient graphene-inorganic heterogeneous catalyst, denoted as Ce–La–Zr–GO nanocomposite. The catalyst was used for the direct synthesis of propylene carbonate (PC) from the cycloaddition of carbon dioxide (CO2) and propylene oxide (PO) in the absence of any organic solvents. Ce–Zr–La–GO nanocomposite was synthesized from pre-mixed aqueous solution of cerium, lanthanum, zirconium nitrate and GO (synthesized via conventional Hummers method) under alkaline conditions using the CHFS reactor. The resulting nanocomposite catalyst was heat-treated at various temperatures (773, 973 and 1173K) and their catalytic properties were assessed. The as-prepared and the corresponding heat-treated catalysts were characterized using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD) and Brunauer–Emmett–Teller (BET) surface area measurements. Effect of various parameters such as heat-treatment temperature, catalyst loading, CO2 pressure, reaction time and temperature was systematically studied to determine the optimum reaction conditions. The optimum reaction condition for the direct synthesis of PC was found at 443K, 70bar and 10% (w/w) catalyst loading. Catalyst reusability study was also conducted to investigate the long life stability for the synthesis of PC and it was found that the catalyst could be reused several times without losing it catalytic activity. These studies revealed that Ce–Zr–La–GO nanocomposite catalyst showed high catalytic activity as compared to other reported heterogeneous catalysts with the conversion of PO, selectivity and yield of PC.

The effect of H2 distribution in (Pb,La)(Zr,Ti)O3 capacitors with conductive oxide electrodes on the degradation of ferroelectric properties

ABSTRACTWe fabricated ferroelectric (Pb,La)(Zr,Ti)O3 (PLZT) capacitors with Sn:In2O3 (ITO) top electrodes using chemical solution deposition. Then, the effects of a thin conductive ITO buffer layer between the Pt bottom electrode and PLZT thin film were investigated in combination with top electrode (ITO/PLZT/ITO/Pt). The H2 degradation resistance of ITO/PLZT/ITO/Pt capacitors with a 3- and 28-nm-thick buffer layer was improved to 78 and 85%, respectively, from 60% without a buffer layer. The time-of-flight secondary ion mass spectrometry profiles indicated the intensity of H ion increased after 45 min forming gas (3% H2/balance N2) annealing.

Effects of crystallinity and impurities on the electrical conductivity of Li–La–Zr–O thin films

We present a study of the fabrication of thin films from a Li7La3Zr2O12 (LLZO) target using pulsed laser deposition. The effects of substrate temperatures and impurities on electrochemical properties of the films were investigated. The thin films of Li–La–Zr–O were deposited at room temperature and higher temperatures on a variety of substrates. Deposition above 600°C resulted in a mixture of cubic and tetragonal phases of LLZO, as well as a La2Zr2O7 impurity, and resulted in aluminum enrichment at the surface when Al-containing substrates were used. Films deposited at 600°C exhibited the highest room temperature conductivity, 1.61×10−6S/cm. The chemical stability toward metallic lithium was also studied using X-ray photoelectron spectroscopy, which showed that the oxidation state of zirconium remained at +4 following physical contact with heated lithium metal.

Compositional and Sr–Nd–Hf isotopic variations of Baijingsi eclogites from the North Qilian orogen, China: Causes, protolith origins, and tectonic implications

Eclogites from the Baijingsi area in the North Qilian orogen at NW China were analyzed for major and trace element abundances as well as Sr, Nd, and Hf isotope ratios to evaluate the impacts from subduction processes on these compositional parameters and to reveal the complexity in protolith characteristics. The major element compositions of the Baijingsi eclogites are within the ranges for basalts. However, the absence of systematic variations among major oxides indicates varying extents of metamorphic modifications. Seven samples are characterized by profound Nb and Ta depletions. Six of them form coherent trends in the La versus Th, HFSE, and LREE plots. They are classified as the Group 1 samples. Other eight samples, referred to as the Group 2 samples, define distinct La–Zr and La–Sm trends and have flat variation patterns with slight Th–Nb–Ta–LREE depletions in the primitive mantle-normalized multiple-element diagram. Group 1 dominates the 87Sr/86Sr–87Rb/86Sr, 143Nd/144Nd–147Sm/144Nd and 176Hf/177Hf–176Lu/177Hf trends for relatively larger variations in the isotope and abundance ratios. Based on the errorchron ages from the samples, closure temperatures of the isotope systems, and isotope ratio versus 1/X plots (e.g., 87Sr/86Sr–1/Sr), it is inferred that the Rb–Sr isotope system was subjected to metamorphic modification, whereas the Sm–Nd and Lu–Hf isotope systems mainly reflect protolith characteristics. In addition to the Nb and Ta depletions, the Group 1 samples generally have εHf(510) values (protolith initial at 510Ma) higher than those of MORB at a given εNd(510), reflecting derivation from relatively high Lu/Hf ratio sources. They also plot within the fields for arc lavas in the Ta/Yb–Th/Yb and Th–Ta–Hf/3 diagrams. All these features are consistent with derivation from protoliths of an arc origin. In contrast, the Group 2 samples have εNd(510) values slightly higher than those of the Group 1 samples at a given εHf(510), plotting on the low εNd(510) margin of the MORB field. They also deviate from the Ta/Yb–Th/Yb trend defined by MORB and OIB toward higher Th/Yb values within the fields of back-arc basin basalts. Therefore, it is inferred that the protoliths of the Group 2 samples were generated as back-arc basin basalts possibly associated with the protoliths of the Group 1 samples in a common supra-subduction zone. The εNd(510)–εHf(510) relationship of the Baijingsi eclogites shows an affinity to the Indian ocean type mantle, implying protolith generation at the southern hemisphere on the margin or a fragment of the Gondwana continent, most likely in the Qilian Block. Based on the current tectonic configuration, a southward subduction is required for protolith generation and might eclogitize the arc protoliths by subduction erosion. Alternatively, the northward subduction in a bidirectional subduction system might become dominant during the amalgamation of the Qilian Block and the North China Craton to eclogitize the arc protoliths in the Qilian Block. Resolving these two possibilities requires more petrological, geochemical, and structural evidence from the North Qilian orogen.

Hydrogen production from oxidative reforming of methane on Ni/γ-Al2O3 catalysts: Effect of support promotion with La, La–Ce and La–Zr

Ni/Al2O3 catalysts promoted by adding La2O3, La2O3–CeO2 and La2O3–ZrO2 were investigated on oxidative and steam reforming aiming the hydrogen production. The samples were characterized by surface area estimation (BET), XRD, TPR, TPD-H2 and XANES. Analysis of TEM and TPO was performed as complementary characterization for catalysts after reaction. The oxidative steam reforming of methane at temperatures above 500°C reveals that all the promoted catalysts presented better activities than the unpromoted. Below 500°C, the catalysts presented deactivation due to metallic nickel species oxidation and the TEM analysis of Ni/Al and Ni/La–Al catalysts revealed that the lanthanum addition led to a decrease in the Ni species particle size and also to a better active phase dispersion. The results suggest that below 500°C the activity may be related to differences in the metallic area values, although the Ni/La2O3–Al2O3 catalysts have shown a different behavior.

Sol–gel derived Li–La–Zr–O thin films as solid electrolytes for lithium-ion batteries

Li–La–Zr–O thin films were successfully fabricated using a sol–gel spin coating method, and the effects of altering the annealing temperature and the number of layers of the films on electrolyte conductivity were studied. Using X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy, the characteristics of these films were investigated as a function of annealing temperature and the numbers of layers of the film. With these methods, an amorphous structure and a smooth surface on the films were revealed. The thin film's ionic conductivity was investigated by impedance analysis. The results show that the ionic conductivity of the films decreases with an increase of the annealing temperature, from 1.67 × 10−6 S cm−1 for 600 °C annealing to 8.53 × 10−7 S cm−1 for 800 °C annealing. The influence of film thickness on conductivity was investigated and the conductivity followed an inverse u-shaped curve with increasing film thickness. We propose that Li–La–Zr–O thin films may be promising solid electrolytes for solid-state lithium-ion batteries.

Efficient and Greener Synthesis of Propylene Carbonate from Carbon Dioxide and Propylene Oxide

Several heterogeneous catalysts have been investigated for solvent-free synthesis of propylene carbonate (PC) for cycloaddition reaction of propylene oxide (PO) and carbon dioxide (CO2). The characterization of different heterogeneous catalysts has been successfully carried out using Raman spectroscopy, scanning electron microscopy, and X-ray diffraction analysis. Batch cycloaddition reaction of PC and CO2 has been conducted in a high pressure reactor. The effect of various parameters that could influence the conversion of PO and the selectivity and yield of PC such as catalyst types, catalyst loading, CO2 pressure, reaction temperature, and reaction time has been studied to find the optimum conditions and the best preferred catalyst for this reaction. Ceria and lanthana doped zirconia (Ce–La–Zr–O) catalyst has been found to be the most active and selective for synthesis of PC as compared to other heterogeneous catalysts that were tested as part of this research. Catalyst reusability studies have been con...

Improved reliability properties of (Pb,La)(Zr,Ti)O 3 ferroelectric capacitors by thin aluminium‐doped zinc oxide buffer layer

Chemical solution deposition (CSD)-derived ferroelectric PbLaZrTiOx (PLZT) capacitors with an aluminium-doped zinc oxide (AZO) top electrode is fabricated. The effects of a thin conductive AZO buffer layer between the Pt bottom electrode and PLZT were investigated. The hydrogen degradation resistance of PLZT capacitors with a 10 and a 20 nm AZO buffer layer was improved up to 91 and 81%, respectively, of an initial polarisation value even after 45 min annealing in a 3% hydrogen atmosphere, from 42% of that without a buffer layer. The fatigue endurance (at 200 kV/cm (10 V) at 100 μs pulse width at 1 ms intervals) of the PLZT capacitor with a 10 nm AZO buffer layer was also improved after 107 cycles.

Hydrogen production through hydrolysis of sodium borohydride: Oleic acid stabilized Co–La–Zr–B nanoparticle as a novel catalyst

OL (Oleic acid)–Cobalt–Lanthanum–Zirconium–Boron nanoparticle was synthesized by chemical reduction of chloride salts of metals in the presence of oleic acid as stabilizing agent. The obtained materials were characterized by XRD (X-ray diffraction), TEM (Transmission electron microscopy), ICP-OES (Inductively Coupled Plasma Optical Emission Spectroscopy), BET (Brunauer–Emmett–Teller) and UV–vis (Ultraviolet–visible) techniques. XRD pattern declares that under Argon atmosphere only metal boride phase has been crystallized and it is not seen any oxide phase of metals. TEM image depicts there are not form any agglomerated nanoparticle. Particle size distribution was prepared and average size particle is about 25 nm. OL stabilized Co–La–Zr–B nanoparticle is active for hydrogen generation from the hydrolysis of sodium borohydride. The reported work also includes the full experimental details for the collection of a wealth of kinetic data to determine the activation energy (Ea = 51.24 kJ mol−1) and effects of the catalyst dosage, amount of substrate, and temperature on the rate for the catalytic hydrolysis of sodium borohydride. Catalytic hydrolysis of NaBH4 is first order with respect to the catalyst concentration and also first order to the NaBH4 concentration in the case of OL stabilized Co–La–Zr–B nanoparticles.

Aluminum-doped zinc oxide electrode for robust (Pb,La)(Zr,Ti)O3 capacitors: effect of oxide insulator encapsulation and oxide buffer layer

Conductive aluminum-doped zinc oxide (AZO) was deposited by pulsed laser deposition as top electrodes for chemical solution deposition derived lanthanum modified lead zirconate titanate (PLZT) capacitors. Compared with PLZT capacitors with Pt top electrodes (Pt/PLZT/Pt), PLZT capacitors with AZO as top electrodes (AZO/PLZT/Pt) showed improved fatigue endurance after cycles of 200 kV/cm (10 V) were applied with a 100 μs pulse width at 1 ms intervals. By using a combination of AZO as the top electrode and as a thin buffer layer (10 nm) under PLZT thin films (AZO/PLZT/AZO/Pt), fatigue behavior was also improved compared with the case without an AZO buffer layer. The addition of either an Al2O3 or HfO2 encapsulation layer increased the remnant polarization ratio of PLZT capacitors (after annealing at 200 °C, 1 Torr, 3 % hydrogen atmosphere) to 0.80 and 0.57, respectively, comparing with 0.52 without an encapsulation layer.

Effect of the morphology of Li–La–Zr–O solid electrolyte coating on the electrochemical performance of spinel LiMn1.95Ni0.05O3.98F0.02 cathode materials

LLZO coated LiMn1.95Ni0.05O3.98F0.02 with controllable microstructure and crystallinity was prepared and studied.

Hydrogen generation from hydrolysis of sodium borohydride by cubic Co–La–Zr–B nano particles as novel catalyst

Cubic Co–La–Zr–B nano particles were prepared in situ for the first time from the reduction of Co(II), La(III) and Zr(IV) chloride by sodium borohydride in methanol under reflux condition. Poly N-vinyl-2-pyrrolidone (PVP) as stabilizing agent was used for preparation of Co–La–Zr–B nano particles. Obtained powders were characterized by XRD, BET, ICP, SEM, TEM and UV–vis techniques. XRD patterns declare that under argon atmosphere only metalboride phase has been crystallized and it was not seen any oxide phase of metals. TEM image depicts that PVP stabilized nano particles are square shaped particles that containing many nanoclusters. Cubic Co–La–Zr–B nano particles were also confirmed by SEM image. Co–La–Zr–B is highly active catalysts for hydrogen generation from the hydrolysis of sodium borohydride. The reported work also includes the full experimental details for the collection of a wealth of kinetic data to determine the activation energy (Ea = 53 kJ mol−1) and effects of the catalyst dosage, amount of NaBH4, and temperature on the rate of the catalytic hydrolysis of sodium borohydride. Catalytic hydrolysis of NaBH4 is first order with respect to the catalyst concentration and also first order to the NaBH4 concentration in the case of cubic Co–La–Zr–B nano particles.

Synthesis and characterization of Co–La–Zr–B quaternary amorphous nano alloy: Kinetic study for hydrogen generation from hydrolysis of sodium borohydride

Abstract Co–La–Zr–B quaternary amorphous nano alloy was for the first time prepared in situ ultrasound-assisted reduction of Co(II), La(III) and Zr(IV) chloride by sodium borohydride aqueous solution. Obtained powder was characterized by XRD, BET, ICP, FE-SEM and TEM techniques. No distinct peak could be observed in XRD pattern of the obtained alloy indicating that the Co–La–Zr–B possessed amorphous structure. Regarding to the size, SEM and TEM images depict that the most of particles are lower than 10 nm and there is no significant aggregation. Co–La–Zr–B nano alloy is highly active catalysts for hydrogen generation from the hydrolysis of sodium borohydride. The reported work also includes the full experimental details for the collection of a wealth of kinetic data to determine the activation energy ( E a = 60.06 kJ mol −1 ) and effects of the catalyst dosage, amount of substrate, and temperature on the rate for the catalytic hydrolysis of sodium borohydride. Catalytic hydrolysis of NaBH 4 is first order with respect to the catalyst concentration and zero order respect to the NaBH 4 concentration in the case of Co–La–Zr–B quaternary amorphous nano alloy.

16-QAM optical packet switching and real-time self-homodyne detection using polarization-multiplexed pilot-carrier

We demonstrated 20-Gbit/s 16 quadrature amplitude modulation (16-QAM) optical packet switching and real-time detection using self-homodyne. A prototype modulator consisting of an in-phase and quadrature (I-Q) modulator and monolithically integrated polarization beam splitters generated modulated signals and polarization-multiplexed pilot-carriers simultaneously. Self-homodyne detection using the pilot-carrier was resilient to phase noise and self-phase modulation, and the constellation was obtained in real time without digital signal processing. A low-polarization-dependent (Pb,La)(Zr,La)O(3) (PLZT) optical switch in the optical packet switch handled both 16-QAM optical packets and the polarization multiplexed pilot-carrier. Even after packet switching, a clear constellation diagram was obtained, and error-free operation was confirmed in real-time using a packet bit-error rate tester (BERT).

Ionic conductivity properties of amorphous Li–La–Zr–O solid electrolyte for thin film batteries

Lithium–lanthanum–zirconium–oxide (Li–La–Zr–O) thin films were deposited using radio-frequency (RF) magnetron sputtering by varying the RF power from 40 to 80W. The characteristics are investigated with X-ray diffraction analysis (XRD) and Field Emission Scanning Electron Microscope (FE-SEM). Results showed that the thin films had amorphous structure accompanied with a smooth, dense, and homogeneous surface. Impedance analysis was conducted to investigate the ionic conductivity. The thin film deposited at 40W gives the highest ionic conductivity of 4×10−7S/cm when compared to both the 60W and 80W samples which show the ionic conductivity of 2×10−7S/cm and 0.8×10−7S/cm respectively. The temperature dependence of the ionic conductivities fit the Arrhenius relation and the thin film deposited at 40W possessed the lowest activation energy. These properties make Li–La–Zr–O thin films as a promising candidate material for use in all-solid-state thin film lithium ion batteries.

Effect of SrTiO3 thickness on the capacitance–voltage characteristics of (La,Sr)CoO3/(Pb,La)(Zr,Ti)O3/SrTiO3/LaVO3 epitaxial heterostructures

We report the effect of SrTiO3 thickness on the capacitance–voltage (C–V) characteristics of (La,Sr)CoO3/(Pb,La)(Zr,Ti)O3/SrTiO3/LaVO3 metal–ferroelectric–insulator–semiconductor (MFIS) epitaxial heterostructures. The C–V measurement of the heterostructure exhibited the asymmetry of capacitance with respect to gate bias. Within the given thickness range (5–30 nm), the amount of capacitance reduction at positive gate bias and the rapidness of capacitance reduction decreased with increasing SrTiO3 thickness, which is consistent with the C–V characteristics of conventional silicon-based MFIS capacitors. These results suggest that quantitative understanding on the electrical behavior of oxide heterostructures is possible with C–V analysis, with potentially important implications on their device applications.