Search query: Microwave synthesis of perovskites

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abstract: Abstract Bismuth vanadate (BiVO4) is considered one of the most successful candidates to be used as photoanode for solar to hydrogen conversion. However, its relatively high recombination rates and considered low long term stability limits its applicability. Doping BiVO4 with tungsten and developing heterojunctions with inorganic perovskites has emerged as strategies to overcome these issues. However, the development of these materials requires plenty of time and energy. Here, we reported the development of a new synthetic method to prepare heterojunctions of tungsten doped bismuth vanadate (using 1, 3 and 5 in mass of W) and tungsten oxide. The heterojunctions were prepared in a one pot microwave assisted method that takes only 24 min. Photocatalytic efficiency was determined through quantification of the amount of hydroxyl radical, generated by the catalysts when they are irradiated with simulated sunlight, and through photoelectrochemical experiments. The heterojunctions showed enhanced photocatalytic activity, which was ascribed to the adequate alignment of the band edges potentials of the semiconductors. Also, the tungsten doping decreases the recombination rates. Both effects increase the photogenerated charges lifetime.
author_names: Caroline H Claudino

Maria Kuznetsova

Barbara Scola Rodrigues

Changqiang Chen

Zhiyu Wang

M R Sardela

Juliana S Souza
title: Facile one pot microwave assisted synthesis of tungsten doped BiVO4/WO3 heterojunctions with enhanced photocatalytic activity
year: 2020

abstract: Abstract La2CuO4/LaFeO3 perovskite nanocomposites were prepared using a microwave combustion technique. The structural characterization by XRD and Rietveld refinements confirmed that Fe3+ substitution in La2CuO4 (LFC) induced the crystallization of secondary LaFeO3 phase. The orthorhombic/cubic nanostructured composites exhibited an average crystallite size in the range 37 47 nm and 14 39 nm, respectively. FTIR spectra revealed bands at 517, 683, and 561 cm 1, characteristics of perovskites orthorhombic and cubic stretching modes. With the increase in Fe3+ doping concentration, the optical band gap increased gradually. Surface morphology showed nanosized crystalline grains agglomerated with spherical and non spherical shapes. The doping dependence of the magnetisation indicated magnetic transition from ferromagnetic to the paramagnetic state at room temperature. The bifunctional nanocomposites La2CuO4/LaFeO3 exhibited excellent catalytic performance and better conversion efficiency (conversion 100% and selectivity 98.6% for glycerol.
author_names: M Sukumar

Lourdusamy John Kennedy

J Judith Vijaya

B Al-Najar

Mohamed Bououdina
title: Facile synthesis of Fe3+ doped La2CuO4/LaFeO3 perovskite nanocomposites: Structural, optical, magnetic and catalytic properties
venue: Materials Science in Semiconductor Processing
year: 2019

abstract: Abstract A series of La0.7 xPrxCa0.3MnO3 (x 0.35, 0.52 or 0.63) perovskites were synthesized using microwave method at different reaction times (3, 4 and 5 min) as possible cathode material for solid oxide fuel cell (SOFCs) SOFCs are a forward looking technology for a highly efficient, environmental friendly power generation. Variation of lattice parameters, unit cell volume and final composition with Pr concentration were analyzed by Rietveld refinement and X ray photo electron spectroscopy (XPS) Thereafter, samples were sintered (at 1000 degC) to evaluate their electrical properties at room temperature. Rietveld refinement showed that all the samples were a single phase perovskite type and belongs to orthorhombic Pnma structure. The atomic composition of doped samples is close to theoretical stoichiometric values. XPS analysis revealed significant changes in the La 3d, Ca 2p, Mn 2p and O 1s intensities as a result of the Pr incorporation.
author_names: A C Ferrel-Alvarez

Miguel A Dominguez-Crespo

Hongbo Cong

Aide Minerva Torres-Huerta

Silvia B Brachetti-Sibaja

W De La Cruz
title: Synthesis and surface characterization of the La0.7 xPrxCa0.3MnO3 (LPCM) perovskite by a non conventional microwave irradiation method
year: 2018

abstract: Low temperature routes have been developed for the preparation of BaCe0,85Y0,15O2,925 (BCY15) in the form of ethanol nanoparticles slurries for use in the central membrane of an original dual cell. Microwave synthesis leads to homogeneous nanoparticles crystalline precursor, as observed by HR TEM and selected diffraction area (SAD) Single phase yttrium doped barium cerate perovskites is obtained, as observed by X ray diffraction, after thermal treatment at 1200degC for 5h. Dynamic temperature X ray diffraction study revealed that BCY phase growth at 850degC. The BCY15 phase can be obtained after 4h at 950degC. This temperature, lower than those usually used for preparation of BCY, lead to small oxide nanoparticles.
author_names: A Gallon

Didier Stuerga

Nicolas Geoffroy

Christoph Lohr
title: New Microwave Synthesis of Yttrium Doped Barium Cerate Nanoparticles Precursor Phase Transformation During Sintering
year: 2011

abstract: Abstract A study on the synthesis of La 1 x Ag x MnO 3+ d x 0, 0.2) using a microwave process (MWhyd) has been carried out by comparing the heating time and reaction temperature with the same factor under conventional thermal process (CHhyd) Experiments have been conducted using the hydrothermal method at medium pressure T 200 degC, P 20 atm) followed by a thermal treatment of the precursor at 700 degC (10 h) Structural and physico chemical properties of the catalysts were investigated using X ray diffraction (XRD) BET sorption, temperature programmed reduction or desorption, mass spectrometry (TPR MS and TPD MS) and X ray photoelectron spectroscopy (XPS) While CHhyd and MWhyd powder catalysts exhibited the same XRD patterns indexed as pure perovskite structure, their surface physico chemical properties were found to be strongly influenced by the preparation method. The effect of the nature of oxygen species, their amount and mobility, evidenced by temperature programmed experiments, on the catalytic properties in methane combustion in the presence and in the absence of hydrogen sulphide has been studied. MWhyd La 0.8 Ag 0.2 MnO 3+ d catalysts were found to exhibit a much better performance in methane combustion together with higher resistance to sulphur poisoning than CHhyd catalysts.
author_names: Simon Ifrah

Akim Kaddouri

Patrick Gelin

Didier Leonard
title: Conventional hydrothermal process versus microwave assisted hydrothermal synthesis of La1 xAgxMnO3+d (x 0, 0.2) perovskites used in methane combustion
year: 2007

abstract: Abstract Hydrothermal microwave method (HTMW) was used to synthesize crystalline bismuth ferrite (BiFeO 3 nanoparticles (BFO) in the temperature of 180 degC with times ranging from 5 min to 1 h. BFO nanoparticles were characterized by means of X ray analyses, FT IR, Raman spectroscopy, TG DTA and FE SEM. X ray diffraction results indicated that longer soaking time was benefit to refraining the formation of any impurity phases and growing BFO crystallites into almost single phase perovskites. Typical FT IR spectra for BFO nanoparticles presented well defined bands, indicating a substantial short range order in the system. TG DTA analyses confirmed the presence of lattice OH groups, commonly found in materials obtained by HTMW process. Compared with the conventional solid state reaction process, submicron BFO crystallites with better homogeneity could be produced at the temperature as low as 180 degC. These results show that the HTMW synthesis route is rapid, cost effective, and could be used as an alternative to obtain BFO nanoparticles in the temperature of 180 degC for 1 h.
author_names: Glenda Biasotto

Alexandre Zirpoli Simoes

Cesar Foschini

Maria Aparecida Zaghete

Jose Arana Varela

Elson Longo
title: Microwave hydrothermal synthesis of perovskite bismuth ferrite nanoparticles
year: 2011

abstract: Orthorhombic structure perovskite LaFeO3 nanocrystals are synthesized by three simple and effective routes using octanoic acid as organic surfactant, namely co precipitation, ultrasonic and microwave assisted co precipitation methods. The phase composition, morphology, lattice parameters and size of nanoparticles in these materials are characterized through Fourier transform infrared spectroscopy, X ray diffraction, scanning electron microscopy, and energy dispersive X ray spectrometer. Magnetic measurements are carried out by a vibrating sample magnetometer on the resultant powders at room temperature. The perovskites synthesized using three methods yield comparatively pure crystalline phase of LaFeO3. However, the particle shape and size ranging changes from short rod like nanoparticles in co precipitation method to sphere like nanoparticles in ultrasonic and microwave assisted co precipitation methods. In addition, the results show that the formation time is decreased considerably by ultrasonic or microwave irradiation.
author_names: Mozhgan Khorasani-Motlagh

Meissam Noroozifar

Akram Ahanin-Jan
title: Ultrasonic and microwave assisted co precipitation synthesis of pure phase LaFeO3 perovskite nanocrystals
venue: Journal of the Iranian Chemical Society
year: 2012

abstract: Abstract The present investigation discusses the synthesis and dielectric properties of three series of oxides of the formula La 2 BaTi 2 M 1 x Cu x O 9 (where M Mg, Zn and Cd) The reactions have been carried out via solid state method and all the compositions crystallize in the disordered cubic perovskite structure. Suitable substitution at both A and B sites lead to enhancement in the dielectric properties at high frequencies. The relative permittivity and loss tangent have been measured at X band (8.2 12.4 GHz) and Ku band (12.4 18 GHz) frequencies. The oxides show a dielectric constant of 20 30 while the dielectric loss is quite low in the order of 10 3 10 4 (at 500 kHz) and 10 2 at X and Ku band. There is scope for further investigations in these systems to realize useful materials for microwave applications.
author_names: Masood A Nath

Saroj L Samal

K Rama Obulesu

Kanakkappillavila Chinnayya James Raju

Ashok Kumar Ganguli
title: Microwave dielectric properties of lanthanum based complex perovskites
year: 2014

abstract: A new strategy for the functionalization of layered perovskites is presented, based on the in situ post synthesis modification of a prefunctionalized phase by copper(I) catalyzed alkyne azide cycloaddition (CuAAC) The microwave assisted protonation and grafting of an alkyne alcohol provides the alkyne functionalized precursor within a few hours, starting from Bi2SrTa2O9. The subsequent microwave assisted in situ "click reaction" allows the post synthesis modification of the precursor within ~2 h, providing a layered perovskite functionalized by an alcohol grafted 1,4 disubstituted 1H 1,2,3 triazole. Two compounds are described here, bearing an aliphatic and an aromatic substituent, which illustrates the general application of the method. This work opens new perspectives for the functionalization of layered perovskites, going beyond mere insertion/grafting reactions, and thus broadens the design possibilities and the range of applications of these hybrid systems.
author_names: Yanhui Wang

Emilie Delahaye

C Leuvrey

Fabrice Leroux

Pierre Rabu

Guillaume Rogez
title: Post Synthesis Modification of the Aurivillius Phase Bi2SrTa2O9 via In Situ Microwave Assisted "Click Reaction"
venue: Inorganic chemistry
year: 2016

abstract: Low dimensional lead halide hybrid perovskites are nowadays in the spotlight because of their improved stability and extensive chemical flexibility compared to their 3D perovskite counterparts, the current challenge being to design functionalized organic cations. Here, we report on the synthesis and full characterization of a perovskite like hybrid (a perovskitoid) where the 1D lead iodide layout is patterned with a donor acceptor charge transfer complex (CTC) between pyrene and tetracyanoquinodimethane, with a chemical formula of (C20H17NH3)PbI3*(C12H4N4) By combining multiple structural analysis and spectroscopic techniques with ab initio modeling, we show that the electronic, optical, and charge transport properties of the hybrid materials are dominated by the organic CTC, with the inorganic backbone primarily acting as a template for the organization of the donor and acceptor molecules. Interestingly, time resolved microwave conductivity (TRMC) measurements show an enhanced photocurrent generation in.
author_names: Nadege Marchal

Wouter T M Van Gompel

Maria C Gelvez-Rueda

Koen Vandewal

Kristof Van Hecke

Hans Gerd Boyen

Bert Conings

Roald Herckens

Sudeep Maheshwari

Laurence Lutsen

Claudio Quarti

Ferdinand C Grozema

Dirk Vanderzande

David Beljonne
title: Lead Halide Perovskites Meet Donor Acceptor Charge Transfer Complexes
venue: Chemistry of Materials
year: 2019