Perovskite Lanthanum Research Articles

Photoelectrochemical Degradation of Organic Pollutants on a La3+ Doped BiFeO3 Perovskite

Towards nonconventional wastewater treatment methods for the degradation of organic pollutants in wastewater, a perovskite-based photoelectrochemical system was developed. Bismuth ferrite doped with lanthanum (La-BiFeO3, La-BFO) perovskite was synthesised through a hydrothermal method with low calcination temperature for the photoelectrochemical degradation of orange II dye and other cocktails of dyes. Photoanodes were prepared by the deposition of the perovskites on a fluorine-doped tin oxide (FTO) substrate. The photoanodes were characterised using XRD, FESEM, FTIR and UV-vis diffuse reflectance. The photoelectrochemical properties of the synthesised photoanodes were investigated with chronoamperometry and electrochemical impedance spectroscopy (including Mott–Schottky analysis). The results show that all La3+-doped BFO photoanodes exhibited a higher absorption edge in the visible light region than the undoped BFO. The photocurrent response of 10% La-BFO (the best performing electrode) exhibited a three times higher current response than the pure BFO. In addition, the electrode exhibited a good degradation efficiency of 84.2% within 120 min with applied bias potential of 2 V at a pH of 7. EIS studies showed a significant enhancement of the interfacial electron transfer of the charge carriers. The enhancements in electrode performances were attributed to the synergistic effect of the applied bias potential and the introduction of La3+ into the BFO matrix. This study therefore shows that the photoelectrocatalytic performance of BFO for water treatment can be improved by the introduction of perovskites-doping ions such as La3+.

E-tirucalli latex mediated green biogenic synthesized Dy3+ doped and Bi3+ co-doped nano perovskite lanthanum aluminum oxide: structure, morphology, luminescence and dielectric studies

E-tirucalli latex mediated green biogenic synthesized Dy3+ doped and Bi3+ co-doped nano perovskite lanthanum aluminum oxide: structure, morphology, luminescence and dielectric studies

A Study on Synthesis and Characterization of Dy-Doped La0.6Sr0.4Co0.2Fe0.8O3−δ via the Coprecipitation Method

The perovskite Lanthanum Strontium Cobalt Ferrite (LSCF) is investigated as the cathode material used in intermediate-temperature solid oxide fuel cells (IT-SOFCs). In the present study, La0.6−xDyxSr0.4Co0.2Fe0.8O3−δ (x = 0, 0.3, 0.6) was synthesized through the coprecipitation method. The obtained precipitate was calcined at 500, 700, 900, and 1000°С. Phase characterization of the synthesized LSCF and LDySCF powder before and after heat treatment at 700°С was carried out by X-ray diffraction (XRD) analysis. XRD patterns revealed that the perovskite phase was obtained at 700°С in all calcined samples. Chemical bond study to investigate the synthesis process was conducted using the Fourier transform infrared spectroscopy technique. Thermal analysis of DTA and TG has been utilized to investigate how the calcination temperature affects the perovskite phase formation. According to the STA results, the perovskite phase formation started at 551°С and completed at 700°С. The density values of synthesized powders were 6.10, 6.11, and 6.37 g·cm−3for the undoped and doped samples calcined at 700°С. Powder morphology was studied by field emission scanning electron microscopy (FE-SEM). The micrographs showed the spherical-shaped particles with the average particle size of 24–131 nm.

Magnetic behavior, photocatalytic activity and gas-sensing performance of porous lanthanum ferrites powders

Porous perovskite lanthanum ferrites (LaFeO3) powders were synthesized under the different pH value by sol-gel technique and self-propagating combustion method. After the characterization with XRD, SEM, VSM, nitrogen adsorption-desorption isotherm and UV–Vis spectroscopy, the magnetic properties, photocatalytic activity and gas-sensing performance are discussed in detail. All LaFeO3 samples exhibit ferromagnetism for the spin mismatch due to oxygen vacancies. LaFeO3 powders present the good photocatalytic performance to MB and could be easily separated by magnetic separation technique after photocatalysis. Furthermore, the LaFeO3 gas sensors exhibited the considerable sensitivity to ethanol gas. Among all samples, LF-1 (LaFeO3 powders prepared at pH = 1) present the highest removal rate of MB (68%), the largest saturation magnetization (4.57 emu/g) and the best gas response to ethanol. The highest response for LF-1 sensor reaches (263.4) at the optimized operating temperature of 250 °C to 100 ppm ethanol gas, which should be attributed to the higher oxygen vacancies.

Crystal structure analysis of Lanthanum Orthoferrite doped Zirconium with sol-gel method for solar cell candidate

Lanthanum Orthoferrite (LaFeO3) is one of the perovskite material which has been studied as a candidate for solar cells. Perovskite doped at site-A and site B was expected to increase efficiency in its application as a solar cell. Zirconium as doping at site-B on LaFeO3 used to reduce the size of crystals with nano size. Therefore, this research has synthesized perovskite lanthanum orthoferrite doped zirconium at site-B (LaFe1-xZrxO3 with x=0.075, 0.1 and 0.15) by the sol-gel method and it has not been studied before. The precursors for these materials are lanthanum Oxide (La2O3), Zirconium (IV) chloride octahydrate (Cl2H12O9Zr), iron nitrate nonahydrate (Fe (NO3)3.9H2O). LaFeZrO3 powder was characterized using X-ray diffraction (XRD) to test the crystal structure properties. The results say that the sample has an orthorhombic structure with Pnma space group. The XRD data has been refined and shows that the lattice parameters for 0.075, 0.1 and 0.15 increase with increasing zirconium concentration and crystal size of LaFeZrO3 decreasing and showing nanosize. Nanosize crystals can maximize the absorption of dyes and it can increase the efficiency of solar cells.

Mechanochemically assisted synthesis of La0.7Sr0.3MnO3 nanoparticles and induction heating properties of the composites with hydroxyapatite

Perovskite lanthanum strontium manganese oxide (LSMO, strontium-substituted lanthanum manganite) La0.7Sr0.3MnO3 nanoparticles were synthesized via the low-temperature calcination of the precursor, which was prepared using a mechanochemical route. A powder mixture of lanthanum chloride, strontium chloride, manganese chloride and sodium carbonate was high-energy milled by a planetary ball mill under semiwet (moist) conditions to obtain the precursor. To study the mechanochemical effects on the formation of LSMO, a thermogravimetric (TG) analysis was conducted for the precursors prepared under various conditions; the precursors and the intermediates formed during calcination were identified by X-ray diffraction (XRD). The calcination of the milled precursor at 600 °C resulted in the formation of LSMO nanoparticles with good induction heating properties. The LSMO/hydroxyapatite composites exhibited rapid temperature increases in an AC magnetic field. The obtained results demonstrate that the LSMO nanoparticles and LSMO/hydroxyapatite composites are promising candidates for magnetic hyperthermia treatments.

Multiple perovskite layered lanthanum nickelate Ruddlesden-Popper systems as highly active bifunctional oxygen catalysts

A systematic study of the Ruddlesden-Popper structured Lan+1NinO3n+1 (n = 1, 2, 3, and 4) and its catalytic performance in oxygen evolution (OER) and oxygen reduction reactions (ORR) is carried out with a view to design a highly-efficient and cost-effective electrocatalyst. In particular, we introduce for the first time a novel La5Ni4O13-δ with a 4-layered perovskite structure (n = 4) for use as a highly active and durable bifunctional oxygen catalyst for OER/ORR. Concretely, La5Ni4O13-δ catalysts has demonstrated performance of 1.65 V at 10 mA·cm−2 and 0.66 V at near half-wave potential (–3 mA·cm−2) for OER and ORR, respectively, this indicates excellent intrinsic OER/ORR kinetics. Furthermore, by controlling the fuel-to-oxidizer ratio (using extremely fuel-rich conditions) in the glycine-nitrate combustion technique, the 4-layered perovskite La5Ni4O13-δ catalysts are synthesized as a single Ruddlesden–Popper phase with various dopants to further boost its bifunctional oxygen electrode activity. Among OER/ORR catalysts, La5Ni3CoO13-δ catalysts exhibit exceptional electrocatalytic activity with low overpotential and Tafel slope (35/76 mV‧dec-1 for OER/ORR). Outstandingly, the La5Ni3CoO13-δ is able to achieve an extremely low overpotential of 370 mV at 10 mA‧cm−2 in 0.1 M KOH for OER, surpassing Ir/C catalysts and any metal oxide catalyst ever reported. The high catalytic performance of La5Ni3CoO13-δ can be attributed to its favorable electronic structure enriched with oxygen defects and electronic charge carriers (increased Ni oxidation state) as well as to the promoted lattice-oxygen oxidation mechanism pathway that comes from strong metal–oxygen covalency (high oxygen-ion diffusion rate).

Perovskite Lithium Lanthanum Titanate-Modified Separator as Both Adsorbent and Converter of Soluble Polysulfides toward High-Performance Li-S Battery

A novel separator constructed by coating a layer of perovskite lithium lanthanum titanate (LLTO)/Super P (SP) composite over a commercial PE membrane was employed for the first time in the Li-S battery (LLTO@Li-S). It was found that the LLTO@Li-S battery possessed an obviously lower impedance but higher Li-ion diffusion than the Li-S battery employing the uncoated separator (Pristine@Li-S). This enabled the soluble polysulfides to be effectively immobilized and further electrochemically transformed into Li2S via the formation of thiosulfate/polythionate intermediates over the LLTO/SP-coated separator during the discharge of the battery. As a result, the shuttle effect was effectively inhibited, and particularly the passivation of both the cathode and “dead S” over the separator was largely decreased. These properties ensured that the LLTO@Li-S battery displayed a significantly high specific capacity and rate capability as well as good cycling stability. For the LLTO@Li-S battery with a S loading of 2 mg cm–2, an initial specific capacity of 1491 mAh g–1 at 0.1C and a residual specific capacity of 459 mAh g–1 at 1C after 1200 cycles had been achieved, while for the LLTO@Li-S battery with a S loading of 5 mg cm –2, an initial specific capacity of 1046 mAh g –1 and a residual specific capacity of more than 800 mAh g–1 at 0.1C after 50 cycles could be delivered.

Room temperature magnetic shape-memory effect in strontium-doped lanthanum cobaltite single crystals

In this study, we investigated the temperature dependence of magnetostriction in the twinned rhombohedral perovskite structure-based lanthanum cobaltite La0.8Sr0.2CoO3. The magnetostriction measured in a magnetic field applied along the pseudocubic [111]c axis showed large hysteresis and residual strains. The residual strains are caused by the twin deformation, which we observed using x-ray diffraction. We found that the critical magnetic field for the twin deformation of La0.8Sr0.2CoO3 increases with temperature. The twin deformation occurs in a sufficiently strong magnetic field (∼6 T), even in the paramagnetic region at room temperature. We also confirmed that the temperature dependence of the critical magnetic field for twin deformation is related to the temperature dependence of the magnetization.

Screen Print Fabricated In3+ Decorated Perovskite Lanthanum Chromium Oxide (LaCrO3) Thick Film Sensors for Selective Detection of Volatile Petrol Vapors

The present work deals with the fabrication of undoped lanthanum chromium oxide and indium doped lanthanum chromium oxide material by cost effective sol–gel method. The four sensors were fabricated by screen printing technique. The indium ion concentration was varied for LaCrO3 material from 0.1 M% to 0.7 M% to access the comparative gas sensing results. All the prepared materials were characterized by XRD, SEM, EDAX, TEM and IR to confirm their structural and chemical composition. The prepared sensors viz. 0.1 M% In3+ doped LaCrO3, 0.3 M% In3+ doped LaCrO3, 0.5 M% In3+ doped LaCrO3 and 0.7 M% In3+ doped LaCrO3 were investigated for gas sensing mechanism for selected gases such as petrol vapours, ethanol, ammonia, NO2, H2S and CO2 gases. The optimum response was recorded for tested gases for all the prepared sensors. The 0.3 M% In3+ doped LaCrO3 found to be exceptional for petrol vapour and highest response was recorded for petrol vapors for 0.3 M% In3+ doped LaCrO3 thick film sensor. All the indium doped are found to be good sensors for petrol vapours and moderate for other tested gases. The prime parameters for the sensors such as selectivity, response and recovery and reproducibility were recorded for the prepared sensor. The response and recovery was very rapid for 0.3 M% In3+ doped LaCrO3 sensor. The gas sensing mechanism for petrol vapours has been established for 0.3 M% In3+ doped LaCrO3 sensor via hole accumulation layer mechanism. The Schematic abstract exhibits the synthesis of In-doped LaCrO3 (0.1M%. 0.3M%, 0.5M% and 0.7M %) by the sol-gel manner. It also illustrates the characterization and optimal gas response to volatile petrol vapors among all the gases.

Fabrication of perovskite lanthanum orthoferrite as a photocatalyst for controlled atom transfer radical polymerization of methacrylate monomers toward an electrolyte material for lead acid batteries

Fabrication of perovskite lanthanum orthoferrite as a photocatalyst for controlled atom transfer radical polymerization of methacrylate monomers toward an electrolyte material for lead acid batteries

Lanthanum‐Based Perovskites for Catalytic Oxygen Evolution Reaction

AbstractLanthanum‐based perovskites have been gaining attention in recent years as cost‐attractive and efficient catalysts for the oxygen evolution reaction (OER). Showing a simplified LaBO3 stoichiometry (B=transition metal cation), the structure and composition of the perovskites play key roles in their electrocatalytic performance. This paper aims to review the physicochemical concepts, structures, and recent advances on kinetic parameters for lanthanum‐based perovskites for catalytic OER. First, advances on mechanisms and descriptors that govern general perovskites will be discussed in detail. Next, the current results for lanthanum cobaltite (LaCoO3), nickelate (LaNiO3), ferrite (LaFeO3), manganite (LaMnO3), and their derivations will be provided. Moreover, the existing results on less explored lanthanum perovskites for catalytic OER (LaCrO3, LaCuO3, LaVO3, and LaTiO3) will be also presented. The impacts of structural defects, orbital occupancy, materials morphology, and composition on the perovskite electrocatalytic performance will be assessed for each case. Finally, emerging trends for lanthanum‐based perovskites will be provided.

Lanthanum Ortho-Ferrite (LaFeO3) Nano-Particles Based Electrochemical Sensor for the Detection of Dopamine

The perovskite type lanthanum ortho ferrite nano-particles (LaFeO3) based electrochemical sensor was developed and used to detect dopamine. For this work the lanthanum ortho ferrite nano-particles (LaFeO3) were synthesized by combustion technique using sugar and ethanolamine with lanthanum oxide and ferric nitrate. For the characterization of newly prepared lanthanum ortho ferrite nano-particles, techniques like FESEM, and TEM were used. The crystallite size was found to be 40 to 46 nm with cubic crystal structure. To check the electrochemical properties of a modified sensor electrode (LaFeO3/GP), the cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques were used. During the experiment, the phosphate buffer solution having pH 6.0 was employed, maintaining the scan rate 100mVs-1 and 50mVs-1 for cyclic voltammetry and Differential pulse voltammetry, respectively.

Photocatalytic La4Ti3O12 nanoparticles fabricated by liquid-feed flame spray pyrolysis

Hexagonal plate-like nanoparticles (NPs) of the layered perovskite La4Ti3O12 were fabricated using liquid-feed flame spray pyrolysis (LF-FSP) followed by subsequent heat-treatments. Their photocatalytic activity was evaluated using decolorization of methyl orange solutions under Uv irradiation. LF-FSP combusts metalloorganic precursor aerosols to produce mixtures of cubic simple perovskite (ABO3) phase and lanthanum oxycarbonate (La2O4·846C0.846) phase with very low agglomeration and average particle sizes (APSs) of 23 nm (as-produced NPs). Rietveld refinement of synchrotron XRD powder patterns verified that the simple perovskite in the as-produced NPs is LaTiO3 (originally cubic Pm-3m-type space group) and heat-treating gives NPs of the trigonal layered perovskite La4Ti3O12 (R-3-type space group). La4Ti3O12 NPs heat-treated at 1100 °C/3-6h/air exhibits hexagonal plate-like morphology and high crystallinity offering enhanced photocatalytic degradation of methyl orange solutions compared to the as-produced NPs. The LF-FSP approach to obtaining layered perovskite La4Ti3O12 NPs provides a simple route to photocatalytic materials in reasonable quantities.

Tweaking the red emission, magneto, and dielectrical properties of perovskite type-LaFeO3 in the presence of Co substitution

Perovskite-structured LaCoxFe1−xO3 (x = 0.05, 0.1, 0.15, 0.2, 0.25) ceramic powders were produced via traditional solid-state reaction method. X-ray diffraction pattern, infrared spectra, and Raman have proved the formation of lanthanum perovskite. The incorporation of Co atoms in host lattice and the distortion of atoms were analyzed using Rietveld refinement method. The microstructure, nominal chemical composition, and uniform distribution of the particles and elements within the LaCoxFe1−xO3 powders were examined by SEM–EDS and elemental mapping. The energy gap (Eg) value sof ceramic powders was estimated using UV–Vis spectroscopy, where the Eg values are in the range of 3.75 eV and 3.92 eV. The interesting red emission at 592 nm was identified by PL spectra. The dielectric behavior such as dielectric constant (e′) and loss (tan δ) decreases with respect to increase in frequency of 10 Hz–1 MHz; on controversy, it increases with increasing temperature (40–200 °C). Magnetic studies clearly show the ferromagnetic (FM) nature of all the samples at room temperature. At higher substituting of Co content (x = 0.25), which has Co–Co interactions can be coupled antiferromagnetically, prominent to the small reduction of Mr and Ms. Hence, the obtained results related to the physical properties of synthesized ceramic powders were investigated.

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.

Impact of nano-perovskite La2CuO4 on dc-conduction, opto-electrical sensing and thermal behavior of PVA nanocomposite films

ABSTRACTNanocomposite (NC) films of poly vinyl alcohol (PVA) incorporated with varying amounts of perovskite lanthanum cuprate (La2CuO4) nanoparticles (NPs) have been fabricated by solution intercalation technique. TEM result showed the size of NPs between 91-134nm. The effects of NPs content on structural and morphological behaviors of PVA have been established by XRD, FTIR and SEM methods. Electrical properties of NC films were performed using LCR-meter. Current (I)–voltage (V) data displayed dc-conductivity increased with increasing NPs content and trends of I–V indicate the dominant Ohmic behavior at voltage <5V and above that Poole–Frenkel emission is the dominant conduction mechanism. Ac-conductivity increases with increase in frequency and dosage of NPs. The maximum ac-conductivity obtained in this investigation is 2.43X10−5S/cm for PVA/2wt% La2CuO4 with lowest activation energy of 0.147 eV at 25°C. Cyclic voltammetry (CV) revealed the specific capacitance of PVA-NC improved compared to pristine PVA. The reduction in Tg with increment NPs contents was observed. The optical behaviors of NCs were deduced by UV-visible spectroscopy where the result showed band gap energy was reduced from 5.23eV to 3.25eV whereas refractive index increased from 1.71 to 2.44 for pure PVA and PVA/2wt%La2CuO4, respectively.

(Keynote) Perovskite Lanthanum Titanium Oxides for Solar Water Splitting

Perovskite lanthanum titanium oxides are very stable but have large band gap and poor charge mobility. This talk presents our effort to tune lanthanum titanium oxides to enhance solar water splitting. Anion doping can result band narrowing while cation doping can increase charge mobility. Incorporation of lanthanum titanium oxides with the reduce graphene oxide sheets to significantly improve the charge extraction from the perovskite oxide. Also, transient absorption spectroscopy has been sued to track the charge dynamics.

Catalytic Properties of Double Substituted Lanthanum Cobaltite Nanostructured Coatings Prepared by Reactive Magnetron Sputtering

Lanthanum perovskites are promising candidates to replace platinum group metal (PGM), especially regarding catalytic oxidation reactions. We have prepared thin catalytic coatings of Sr and Ag doped lanthanum perovskite by using the cathodic co-sputtering magnetron method in reactive condition. Such development of catalytic films may optimize the surface/bulk ratio to save raw materials, since a porous coating can combine a large exchange surface with the gas phase with an extremely low loading. The sputtering deposition process was optimized to generate crystallized and thin perovskites films on alumina substrates. We found that high Ag contents has a strong impact on the morphology of the coatings. High Ag loadings favor the growth of covering films with a porous wire-like morphology showing a good catalytic activity for CO oxidation. The most active composition displays similar catalytic performances than those of a Pt film. In addition, this porous coating is also efficient for CO and NO oxidation in a simulated Diesel exhaust gas mixture, demonstrating the promising catalytic properties of such nanostructured thin sputtered perovskite films.

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.