Lanthanum Acetate Hydrate Research Articles

Synthesis of anhydrous lanthanum acetate. Analysis of it’s structural, thermal and electronic properties

Acetate complexes of rare earth elements are extensively studied compounds known for their diverse properties and potential applications and lanthanum acetate hydrate is commercially available. In this work, a powdered anhydrous lanthanum acetate (La(CH3COO)3) sample was prepared by dissolving lanthanum oxide (La2O3) in an excess of acetic acid (CH3COOH) and distilled water (H2O), followed by direct evaporation at 150 °C. The decomposition of La(CH3COO)3 was studied, showing initiation around 300 °C and conclusion at ≥700 °C, with four distinct thermal events (I–IV) of mass loss. Gas phase identification revealed acetone and carbon dioxide as decomposition products, indicating pyrolytic decarboxylation. The final thermal effect (IV) is linked to the decomposition of La2O2CO3 to La2O3. The DFT refinement of atomic coordinates of hydrogen atoms, which were unavailable from experiment, was successfully performed. Obtained structural data was checked using vibrational spectroscopy method. The calculated electronic band structure of La(CH3COO)3 indicates it as an indirect wide band gap material with values of direct transition close to indirect. The optical bandgap is found to be 5.49 eV, suggesting that the charge transfer in La(CH3COO)3 can be optically activated with wavelengths shorter than 226 nm, which falls within the deep UV (DUV) region.

Facile synthesis of lanthanum carbonate octahydrate and lanthanum oxide nanoparticles by sonochemical method: systematic characterizations

Abstract This study could present the size and morphology of two synthesized nanoparticles (NPs) by observing their smallest possible dimensions. Lanthanum carbonate nanoparticles were synthesized by sonochemical method through the interaction of lanthanum acetate hydrate and sodium carbonate in an aqueous medium with a probe sonicator. After rigorous washing followed by drying, the La2(CO3)3·8H2O(S1) NPs were calcined at a temperature of 600 °C to obtain lanthanum oxide nanoparticles (S2). Both NPs were characterised through various instrumental techniques. PXRD study showed orthorhombic with space group of Pccn (56) and hexagonal phases with space group of P 3 ‾ m 1 $P\overline{3}m1$ (164) for S1 and S2 respectively whose morphology and elemental analysis were studied through FESEM and EDX. High resolution TEM image of La2(CO3)3·8H2O and La2O3 showed spherical shapes of the nanoparticles. Further study of XPS and FTIR conveyed detailed information of both nanoparticles whose TGA-DSC showed three step decomposition curves. The size and morphology of the synthesized nanoparticles have been found to have a distinct morphology and are found comparatively smaller in size than those observed in the earlier reported works (Table 1 Table 1: Comparative study of synthesized lanthanum carbonate and lanthanum oxide NPs with various techniques applied by other researchers. Sl. no. Name of NPs Methods Conditions Size of NP Reference 1 La2(CO3)3·8H2O Sonochemical method Time: 25 min XRD: Pccn (56) a = 8.9840 Å b = 9.5800 Å c = 17.0000 Å This work Temperature: 301 K Size: 24.102 nm Starting materials:(a) La(CH3COO)2: 0.050 M(b) Na2CO3:0.050 M TEM: Size: 4–30 nm La2(CO3)3 Reverse micelles Time: 1 h XRD: Size: nanoparticles absent [20] Temperature: 303 K Starting materials:(a) Triton X-100(b) Cyclohexane(c) n-butylalcohol(d) La(NO3)3(aq) e) NaCO3(aq) La2(CO3)3·8H2O Hydrothermal Time: 2–5 days XRD: Pccn a = 8.984 Å b = 9.580 Å c = 17.00 Å [21] Temperature: 773 K Size: nanoparticles absent Prepared by slow hydrolysis of La(CCl3COO)3 La2(CO3)3·1.4H2O Hydrothermal Time: 1 h 30 min Structure unknown [22] Temperature: 368 K Starting material:(a) La2O3 (b) HNO3 (c) Urea La2(CO3)3·1.7H2O Sonochemical Time: 30 min XRD: a = 8.990 Å c = 9.675 Å [23] Temperature: not specified Size: not specified (a) La(OAC)3 (b) Na2CO3 TEM: Size: 25–35 nm Concentration:(a) La(OAC)3: 0.051 M(b) Na2CO3: 0.251 M La2(CO3)3·5H2O Hydrothermal Time: XRD: Pbca a = 9.0167 Å b = 12.842 Å c = 9.6331 Å [24] Temperature: Size: not specified Starting materials:(a) La2O3 (b) HCl(c) Na2CO3 La2(CO3)3·3.4H2O Hydrothermal Time: 3–4 h XRD: P21212 a = 9.57 Å b = 12.65 Å c = 8.94 Å [25] Temperature: 298–308 K Size: not specified Starting materials:(a) LaCl3 (b) NH4HCO3 2 La2O3 Thermal decomposition Time: 2 h P3m1 a = 3.973 Å b = 3.9373 Å c = 6.129 Å [26] Temperature: 1073 K Size: 15 nm Starting material: La(OH)3 nanorods TEM: Size: 23 nm La2O3 Thermal decomposition Time: 2 h XRD: a = 11.347 Å [23] Temperature: 873 K Size: 30 nm Starting material:La2(CO3)3·1.7H2O TEM: Size: 30 nm La2O3 Thermal decomposition Time: not specified Not specified [27] Temperature: 1198 K Starting material:(a) La(NO3)3·9H2O(b) NH4HCO3 La2O3 Thermal decomposition Time: 4 h Not specified [28] Temperature: 1073 K Starting material: La(OH)3 La2O3 Thermal decomposition Time: 2 h P 3 ‾ m 1 $P\overline{3}m1$ a = 3.973 Å b = 3.9373 Å c = 6.129 Å This work Temperature: 873 K XRD: Size: 43.26 nm Starting material: La2(CO3)3·8H2O TEM: Size: 17–34 nm ).

Synthesis and performance of La2O3@MWCNT composite materials as Pt-free counter electrodes for dye-sensitized solar cells

Pt-free composite counter electrode (CE) composed of La2O3 was successfully synthesized by a simple pyrolysis of Lanthanum acetate hydrate (La(CH3COO)3·xH2O) in a high-temperature solid phase. Furthermore, three proportion composite catalysts of La2O3@MWCNTs based on La2O3 and multiwall carbon nanotubes (MWCNTs) were prepared and characterized as Pt-free catalysts for CE in dye-sensitized solar cells (DSSCs). The morphology and structure of La2O3@MWCNT composites were determined by scanning electron microscopy and X-ray diffraction. The electrochemical performance of La2O3@MWCNT composite catalysts for CEs was determined by photocurrent-voltage measurements, cyclic voltammetry, electrochemical impedance spectroscopy, and Tafel polarization. The experimental results showed that the power conversion efficiencies of 5.20, 5.12, and 4.70% were obtained for La2O3: MWCNTs with mass ratios of 5:1, 3:1, and 1:1 as counter electrode towards the reduction of I3−/I− ions respectively in the encapsulation of DSSC batteries, which were higher than that of MWCNTs (3.94%) and La2O3 (0.77%) electrode under the similar conditions. The enhanced electrode performance was attributed to relatively larger surface area and higher conductivity of La2O3@MWCNT composite catalysts.

Preparation, Characterization and Electrochemical Study of Lanthanum-Silica Sol-Gel Thin Films

This work presents a low cost environmentally friendly alternative to corrosion protection of aluminium alloy based on silica sol-gel thin films doped with lanthanum compounds. Sols were prepared from solutions composed of tetraethylorthosilicate and methyl-triethoxysilane as precursors, distilled water to perform the hydrolysis, absolute ethanol as solvent and nitric acid as catalyst. Lanthanum acetate hydrate or lanthanum isopropoxide in three different concentrations were added as doping agents. These lanthanum compounds can play as the well-known Cr (VI) salts offering a suitable protective effect without any environmental negative impact. L-cysteine as green corrosion inhibitor has been also added to a set of sol formulations. Films were deposited upon microscope glass slides and aluminium alloy AA2024-T3 sheets by dip coating at a constant drawing speed (2.0 mm·s−1), in a controlled room under 25°C and 35% relative humidity. For convenience, sol-gel monoliths of 20 mm diameter were also prepared. After coating, monoliths and films were dried and annealed in air at 20, 100 and 500 °C. A model polyvinyl butyral film was applied on a series of these sol-gel coatings to simulate the performance of commercial anticorrosive paints (organic coatings). For this matter poly (vinyl butyral-covinyl alcohol-co-vinyl acetate) solutions (17% w/w) were prepared in ethanol. Transmission spectra of the as prepared films were recorded with a UV–VIS-NIR double-beam spectrophotometer equipped with an integrating sphere. Optical measurements (from UV-Vis absorption and diffuse reflectance spectroscopies) pointed out that the coatings were colourless and transparent, and they diminish the diffuse reflectance of the metallic surface up to ∼60 %. Scanning electronic microscopy coupled with energy dispersive spectroscopy (SEM-EDS), atomic force microscopy (AFM) and contact angle measurements were also applied for the coatings characterization. As concerns the structural characterization of the lanthanum environment X-ray Absorption Fine Structure (XANES) and X-ray Absorption Near Edge Structure spectroscopy (EXAFS) were also performed. Likewise, the remaining sols were kept to gelify at 60 °C for 4 days and then powdered to obtain suitable samples to be analysed by using other characterisation techniques (Fourier transformed infrared, FTIR, and differential thermal analysis, DTA). The corrosion resistance of the sol-gel coated AA2024-T3 aluminium alloy was studied by weathering tests according to modified ISO 1776 and 695 Standards. Samples were immersed into an acid solution (HCl 0.1 N at 25 °C) or into a basic one (NaOH 0.1 N at 25°C) for 1 h. In parallel studies, anodic and cathodic delamination tests were also carried out during immersion of coated samples into a 0.6 M NaCl aqueous solution. Just before the experiment was initiated, the centre of the PVB/sol-gel thin film/metal samples was damaged with an intentionally scribed linear defect. Potentiodynamic polarization technique and global and electrochemical impedance spectroscopy were also applied. The results show that the presence of lanthanum compounds and L-cystiene induces an effective delay of early corrosion of metallic substrates, demonstrated by accelerated corrosion tests in acid and basic media. XAS studies confirmed the incorporation of lanthanum ions into silica sites to be essential for the material anticorrosive properties. Optical and scanning electron microscopies allowed the coated samples texture and microstructure observation, both before and after the corrosion tests were carried out. These last two techniques joined with the electrochemical studies allowed to evaluate not only the inhibitor effect of lanthanum compounds and L-cysteine, but also the self-healing properties of the studied systems. As concluding remarks, we may indicate the convenience and effectiveness of the prepared sol-gel silica films doped with lanthanum isopropoxide or lanthanum acetate as a protective barrier for the delay of early corrosion of metallic surfaces. These properties are scarcely dependent on the lanthanum precursor used, which could be selected taking in mind the corresponding cost. Depending on the reaction parameters in the sol-gel process, La2O3 or La(OH)3 nanoparticles can be intentionally produced. The combination of these La2O3 nanoparticles with L-cysteine produces a synergic effect which improves considerably the corrosion protection behaviour of sol-gel coated AA2024-T3 aluminium alloy in NaCl aqueous solutions. The uniformly distributed La2O3 or La(OH)3 nanoparticles impregnated with corrosion inhibitor behave as active fillers and nanoreservoirs for the sol-gel thin film, providing a prolonged and smart release of the corrosion inhibitor (L-cysteine) in response to local pH changes during the samples contact with the aqueous solutions. The action of the organic inhibitor combined with the precipitation of insoluble lanthanum products from the inorganic framework at the cathodic and anodic corrosion zones, provides self-healing properties to the protective system, avoiding the corrosion processes as expected. Acknowledges: This work was supported by MINECO, Spain (Projects MAT2012-38541-C02-02, MAT2015-65445-C2-1-R and MAT2015-65445-C2-2-R).

Chemical solution deposited lanthanum zirconium oxide thin films: Synthesis and chemistry

Pyrochlore lanthanum zirconium oxide (LZO) thin films textured along 〈4 0 0〉 are synthesized using lanthanum acetate hydrate, zirconium propoxide, propionic acid, acetic acid glacial, and methanol as precursors. The materials growth and chemistry are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and thermal gravimetric analysis (TGA). The formation of inkjet printed LZO films on Ni-5%W tape is found to be based on the decomposition of the LZO precursor solution. In the annealing process, Zr metal–oxides bonds are first eliminated between 150 and 250 °C, while carboxylates from precursors remain in LZO after the annealing carried out at 900 °C for an hour. Annealed LZO films have dense and smooth structure that are composed of nanoparticles sizing 10–15 nm and some pinholes sizing 25–35 nm accounted for less than 0.1% of the area are observed.

Solvent-Free Fabrication of Rare LaCO3OH Luminescent Superstructures

Lanthanum hydroxycarbonate (LaCO(3)OH) superstructures [LHS] decorated with carbon spheres are synthesized by a solvent-free, one-pot Reactions under Autogenic Pressure at Elevated Temperature (RAPET) process, dissociating a single lanthanum acetate hydrate (LAH) precursor. The structure of the as-synthesized LHS are studied by powder X-ray diffraction, high-resolution transmission electron microscopy, morphology by field-emission scanning electron microscopy, and the composition by energy dispersive X-ray analysis, elemental mapping, as well as FT-IR spectroscopy. The photoluminescence results showed an emission band centered at 465 nm (lambda = exc. 360 nm) for the hexagonal phase of LHS. The mechanistic elucidation for the fabrication of LaCO(3)OH decorated with carbon spheres is developed on the basis of obtained thermal [TGA and DTA] data on initial LAH reactant.

Study on chemical-solution-deposited lanthanum zirconium oxide film based on the Taguchi method

A statistical route, Taguchi Design, applied to the analysis of experimental factors for coating lanthanum zirconium oxide films on metal substrates by inkjet printer is presented. The synthesis of lanthanum zirconium oxide precursor is derived from a chemical solution containing lanthanum acetate hydrate, zirconium propoxide, propionic acid, glacial acetic acid, and methanol anhydrous. Experimental factors analyzed by Taguchi Design show that the ratio of lanthanum acetate to propionic acid and the concentration of precursor used for inkjet printing are the dominant factors for the quality of films. With the deduced optimum conditions, lanthanum zirconium oxide films reveal good surface morphology and high out-of-plane alignment that is consistent with the Taguchi prediction.

Dynamic dielectric response of PLZT-P(VDF/TFE) nanocomposites

Dynamic dielectric relaxation of polymer P(VDF/TFE)(0.98/0.02) loaded with lead lanthanum zirconate titanate (Pb0.92La0.08)(Zr0.65Ti0.35)O3(PLZT 8/65/35) ceramic nanopowders was studied in the frequency range from 100 Hz to 1 MHz and at temperatures from 100 K to 450 K. The PLZT nanopowders were prepared by the sol-gel method using: lead(II)acetate trihydrate, lanthanum acetate hydrate, zirconium(IV)propoxide and titanium(IV)propoxide. The crystallization process of PLZT powders was monitored by means of XRD analysis (Philips PW 3710) using Cu-Kα radiation in the range 20° ≤ 2Θ ≤ 60°. The powders were analyzed before and after burning of the organic remains. The morphology observations of the powders were made using Hitachi S-4700 scanning electron microscope (SEM), and the grain size distributions were measured on a Zetasizer Nano ZS by the DLS method. The PLZT-P(VDF/TFE) composite samples of 0-3 connectivity were prepared from ceramic and polymer powders by the hot-pressing method. The volume fraction of the ceramics Θ amounted 0.1, 0.15 and 0.2. The dielectric response of the ceramics-polymer composite was found as a combination of the responses of pure polymer and the ceramics: (i) the addition of the PLZT ceramics increases the value of the dielectric permittivity ϵ, (ii) the composite shows the maximum of the permittivity coming from the PLZT ceramics, (iii) the dielectric absorption spectrum of the composites is dominated by the α-relaxation in pure polymer.

Electrical and optical properties of sol–gel derived La modified PbTiO3 thin films

Lanthanum modified lead titanate (Pb1−xLaxTi1−x/4O3) PLTx (x=0.08 i.e. PLT8) sol–gel derived thin films have been prepared on indium tin oxide (ITO) coated glass and quartz substrates using lead acetate trihydrate, lanthanum acetate hydrate and titanium isopropoxide as precursors along with 2-methoxyethanol as solvent and acetic acid as catalyst by spin coating method. The microstructure and surface morphology of the films annealed at 650°C have been studied by X-ray diffraction technique and atomic force microscope (AFM). XRD has shown a single phase with tetragonal structure and AFM images have confirmed a smooth and crack-free surface with low surface roughness. The dependence of leakage current on applied voltage show ohmic behavior at low field region with a space charge conduction mechanism at high fields. The wavelength dispersion curve of thin films obtained from the transmission spectrum of thin films show that the films have high optical transparency in the visible region.

Preparation and characterization of dense Pb1 – xLaxTiO3 (x = 0.0∼0.2) fibers through the sol–gel-related solvothermal process

Dense Pb1 − xLaxTiO3 (PLT, x = 0.0∼0.2) ceramic fibers were prepared by the sol–gel-related solvothermal method using lead acetate trihydrate, lanthanum acetate hydrate and titanium isopropoxide as the starting materials. The as-drawn fibers were pretreated in organic solvents, dimethylbenzene and triethylamine, using the solvothermal process prior to the heat treatment for crystallization so as to dehydrate the fibers in situ, remove the organic components and to improve the densification of the precursor fibers. The effects of the solvothermal treatment on the structure and composition of the resultant dense, crack-free transparent PLT ceramic fibers have been investigated. Furthermore, the PLT fibers have been characterized by IR, XRD, SEM, TEM and other techniques.

Selective Benzylic Bromination of 2-Methylnaphthalene

A practical synthesis of 2-(bromomethyl)naphthalene (1), by selective benzylic bromination of 2-methylnaphthalene (2), with bromine in heptane in the presence of lanthanum acetate hydrate is described.

Spectrothermal investigation of the decomposition course of lanthanum acetate hydrate

Thermogravimetry, differential thermal, X-ray diffraction and infrared spectroscopy analyses showed La(CH3COO)3·1.5H2O to decompose completely at 700°C yielding La2O3. The results revealed that the compound dehydrates in two steps at 130 and 180°C, and recrystallizes at 210°C. Water thus produced hydrolyzes surface acetates (at 310°C), releasing acetic acid into the gas phase. At 334°C, the anhydrous acetate releases gas phase CH3COCH3 to give La2(CO3)3 residue, which decomposes to La2O2(CO3) via the intermediate La2O(CO3)2. On further heating up to 700°C, La2O3 is formed. IR spectroscopy of the gaseous products indicated a chemical reactivity at gas/solid interfaces formed throughout the decomposition course. As a result, CH3COCH3 was involved in a surface-mediated, bimolecular reaction, releasing CH4 and C4H8 (isobutene) into the gas phase.

Reactions taking place during the sol-gel processing of PLZT

PLZT gels were prepared from lead acetate hydrate, lanthanum acetate hydrate, titanium isopropoxide and zirconium n-propoxide in methoxyethanol by the sol-gel method. For the purpose of the present study 1HNMR and GLC analyses were performed for quantitative determination of the volatile reaction products formed during the sol preparation. It was found that Pb and La acetates partly reacted with methoxyethanol in the first step of sol preparation. The results also indicated that Zr and Ti propoxides reacted with the acetates during refluxing. In addition, significant alcoholysis of Ti and Zr propoxides also occurred. On the basis of the results the extent of precursor conversion was calculated.

Fabrication and characterization of ferroelectric PLZT 7/65/35 ceramic thin films and fibers

Integration of ferroelectrics in the current generation of electronic/photonic devices not only enhances the functional capabilities of these devices but also has potential for a variety of new applications. The fabrication of ceramic thin films and fibers is enabled by sol-gel process. This fabrication process is well-controlled, low-cost and compatible with existing fabrication technologies. This study focussed on the fabrication of PLZT 7/65/35 ceramic thin films and fibers from lead acetate hydrate, lanthanum acetate hydrate, zirconium n-propoxide and titanium n-propoxide utilizing acid catalysis. The transformations of the precursors to sol, sol to gel and gel to crystalline phase were characterized using spectroscopy and x-ray diffraction. The films were formed by spin-coating the hydrolyzed precursor sol on various substrates: conductors (Au, Al, Pt), semiconductors (Si [100], Si [111]) and insulators (fused SiO2, Al2O3, MgO). The fibers were drawn from the similar sols. These films and fibers were characterized utilizing various techniques.