MgTiO3 (MTO) thin films were prepared by the
polymeric
precursor method with posterior spin-coating deposition. The films
were deposited on Pt(111)/Ti/SiO2/Si(100) substrates and
heat treated at 350 °C for 2 h and then heat treated at 400,
450, 500, 550, 600, 650 and 700 °C for 2 h. The degree of structural
order–disorder, optical properties, and morphology of the MTO
thin films were investigated by X-ray diffraction (XRD), micro-Raman
spectroscopy (MR), ultraviolet–visible (UV–vis) absorption
spectroscopy, photoluminescence (PL) measurements, and field-emission
gun scanning electron microscopy (FEG-SEM) to investigate the morphology.
XRD revealed that an increase in the annealing temperature resulted
in a structural organization of MTO thin films. First-principles quantum
mechanical calculations based on density functional theory (B3LYP
level) were employed to study the electronic structure of ordered
and disordered asymmetric models. The electronic properties were analyzed,
and the relevance of the present theoretical and experimental results
was discussed in the light of PL behavior. The presence of localized
electronic levels and a charge gradient in the band gap due to a break
in the symmetry are responsible for the PL in disordered MTO lattice.
Este trabalho descreve a síntese e a caracterização de BiFeO 3 obtido a partir da rota Pechini, utilizando-se nitrato de bismuto e nitrato de ferro como precursores. Os pós foram calcinados a 800 °C em ar durante 2 h. Os difratogramas de raios X mostraram que o material apresenta duas fases, BiFeO 3 (95%) e α-Bi 2 O 3 (5%). A transição de fase ferroelétrica da amostra em 821 °C foi detectada por análise térmica diferencial. Os resultados das análises por microscopia eletrônica de varredura (SEM), espectroscopia de energia dispersiva (EDS) e fluorescência de raios X por dispersão de energia (EDX) mostraram que a amostra é quimicamente homogênea. As imagens de microscopia eletrônica de transmissão revelaram que a amostra é uniforme e apresenta partículas com formato esférico e tamanho médio de 30 nm.This work describes the synthesis and characterization of BiFeO 3 obtained by the Pechini route using bismuth nitrate and iron nitrate as precursors. The powders were annealed at 800 °C in air for 2 h. X-ray diffraction patterns showed that the material presents two phases, BiFeO 3 (95%) and α-Bi 2 O 3 (5%). The ferroelectric transition of the sample at 821 °C was detected by differential thermal analysis. Results of analyses by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and energy dispersive X-ray fluorescence (EDX) showed that the sample is chemically homogeneous. Transmission electron microscopy images revealed that the sample is uniform and contains spherical particles with an average size of 30 nm.
Keywords:Pechini method, X-ray diffraction, ferroelectricity, magnetic properties
IntroductionMultiferroic magnetoelectric materials are known to exhibit magnetic (ferro, anti, or ferri) and electric (ferro) ordering simultaneously at room temperature, 1 as well as interesting physical properties with possible practical applications, as in new memory devices whose polarization and magnetization states and coupling can be simultaneously exploited.2-6 BiFeO 3 is one of these few materials, along with YMnO 3 and BiMnO 3 , that have all the potential applications of both their parent ferroelectric and ferromagnetic materials.Bismuth ferrite, BiFeO 3 , belongs to the perovskite class of materials with a rhombohedrally distorted unit cell. It has the polar R3c space group, whose ions are displaced along the [111] direction relative to the ideal centrosymmetric positions.7,8 Detailed structural investigations of BiFeO 3 can be found elsewhere.9,10 The interest in this compound is due to its ferroelectric behavior with a high Curie temperature (T C ca.1100 K) and its antiferromagnetic behavior with a relatively high Néel temperature (T N ca. 650 K).7,11 Both BiFeO 3 thin films and ceramics have been intensively investigated in the last years.
11-19Multiferroic BiFeO 3 was discovered in the 1960s and its properties have been extensively studied. However, the electrical properties of pure BiFeO 3 have rarely been reported on and it has no commercial applications due to its room-temperature low resist...
Calcium titanate zirconate, Ca(TiZr)O (CZT), powders have been synthesised by the polymeric precursor method. The structural analysis of the CZT powders was monitored by X-ray diffraction (XRD), photoacoustic spectroscopy (PAS) and textural analysis. The photocatalytic properties were evaluated by methylene blue (MB) decomposition and real textile wastewater (RTW) combined treatment (coagulation/flocculation/photocatalysis). Chemical oxygen demand (COD) of RTW was successfully reduced from 6195 mg L (untreated) to 662 mg L after coagulation/flocculation with a tannin-based coagulant (Tanfloc®) and finally to 471 mg L after combined treatment (coagulation/flocculation/photocatalysis) applying ultraviolet radiation and CaTiO as photocatalyst.
RESUMO No presente trabalho, utilizou-se a caulinita como material base para a obtenção de materiais nanocompósitos. A caulinita foi utilizada na forma in natura, tratada termicamente à 700 ºC e quimicamente com ácidos fosfórico e sulfúrico na concentração de 6 mol L-1. O objetivo dos tratamentos foi modificar e preparar a estrutura da caulinita para ser usada como um suporte para o TiO2. Por meio do método dos precursores poliméricos foi sintetizado o TiO2 e nanocompósitos à base de caulinita e TiO2. Os nanomateriais foram caracterizados por Difratometria de Raios X (DRX), UV-Vis, para determinar o Bandgap, Espectroscopia na Região do Infravermelho com Transformada de Fourier (FTIR), Microscopia Eletrônica de Varredura (MEV) e Espectroscopia de Energia Dispersiva (EDS). Por meio dos espectros de FTIR foi possível verificar as bandas características da caulinita in natura e o aparecimento de vibrações características da metacaulinita. A análise de DRX revelou que foi possível promover o aumento da cristalinidade das amostras de caulinita após tratamento com o citrato de titânio, isto pode ser decorrente da adesão do óxido de titânio na superfície da caulinita. Pela análise de EDS foi possível determinar a porcentagem de Ti (m/m) nas amostras sintetizadas, sendo que seu valor ficou entre 2,03 e 4,16 %. As análises por ICP-OES indicam que as amostras apresentam de 2,65 a 4,07% de Ti e os dados do Bandgap variam de 1,69 a 3,44 eV para as amostras com e sem Ti em sua composição.
RESUMOO efluente têxtil tem alta intensidade de cor e grande concentração de contaminantes orgânicos geralmente não sendo totalmente degradado através dos tratamentos convencionais, necessitando assim de um tratamento avançado como o de fotocatálise heterogênea. O material cerâmico tipo peroviskta MgTiO 3 é um semicondutor que tem características que possibilita sua utilização como um fotocatalisador. O presente trabalho tem como objetivo estudar a degradação de efluente têxtil utilizando a peroviskta MgTiO 3 como fotocatalisador. O MgTiO 3 mostrou-se eficiente tanto para degradação de solução sintética de corante quanto para o efluente têxtil, mostrando ser um potencial fotocatalisador.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.