A first-principles investigation on the luminescence emissions of BaZrO3 obtained by microwave-assisted hydrothermal method

Gouvêa, Rogério Almeida; Flores, Efracio Mamani; Cava, Sergio; Moreira, Mário L.

doi:10.1016/j.jlumin.2016.07.023

Cited by 4 publications

(3 citation statements)

References 30 publications

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“…There are several reports on the electronic structure calculations performed to study CZO in the ground state [50][51][52][53][54][55]. Recently, Gupta et al [56] have been performed a spectroscopic and theoretical study to explain the PL emission in the blue region based on the nature of defects, while Moreira et al [57] employed first-principles calculations to clarify the mechanisms involved in the luminescence emissions observed for disordered BaZrO3, proposing a novel explanation for transitions from a PL and to a radioluminescence emission regime based on crystalline defects. The remainder of the paper is organized as follows; the analysis and discussion of both theoretical and PL results are presented in Section 3.…”

Section: Octahedral Rotations Provoke Changes In the B-o And A-o Bondmentioning

confidence: 99%

Mechanism of photoluminescence in intrinsically disordered CaZrO3 crystals: First principles modeling of the excited electronic states

Oliveira

Gracia

Assis

et al. 2017

Journal of Alloys and Compounds

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CaZrO3 (CZO) powders were synthesized at different temperatures (400, 600, 800, and 1000 °C) and characterized by X-ray diffraction, Raman and ultraviolet-visible spectroscopic methods, along with photoluminescence (PL) emissions. First principle calculations based on the density functional theory (DFT), using a periodic cell models, provide a theoretical framework for understanding the PL spectra based on the localization and characterization of the ground and electronic excited states.Fundamental (singlet, s) and excited (singlet, s*, and triplet, t*) electronic states were localized and characterized using the ideal and distorted structures of CZO. Their corresponding geometries, electronic structures, and vibrational frequencies were obtained. A relationship between the different morphologies and structural behavior has also been established. Polarized structures were identified by the redistribution of the 4dz2, 4dyz, and 4dxy (Zr) orbitals at the conduction band and the 2pz (O) orbital in the valence band for s, s* and t*. Analysis of the vibrational eigenvector modes of these electronic states reveals a relationship between them via asymmetric bending and stretching modes that arise from Zr atom displacements due to polyhedral [ZrO6] distortion. Furthermore, the results provided an insight into the PL emissions of the as-synthesized CaZrO3 and led to the conclusion that the presence of electronically excited states is strongly related to the structural order-disorder effects (polyhedral distortion) at short range for both [ZrO6] and [CaO8] clusters.

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Section: Octahedral Rotations Provoke Changes In the B-o And A-o Bondmentioning

confidence: 99%

Mechanism of photoluminescence in intrinsically disordered CaZrO3 crystals: First principles modeling of the excited electronic states

Oliveira

Gracia

Assis

et al. 2017

Journal of Alloys and Compounds

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“…There are several reports that discussed the electronic states in defective BaZrO 3 from the viewpoint of fluorescent materials: First-principles simulations have revealed that the valence and conduction bands of ideal BaZrO 3 are derived from the O 2p orbital and the Zr 4d orbital, respectively, suggesting a strongly covalent electronic state of the octahedral ZrO 6 cage. Vacancies at the Ba and Zr sites of this crystal lead to hole doping, while oxygen vacancies lead to new defect levels at the mid gap. , This latter defect forms the F-center where electrons are trapped in the oxygen vacancy, but when a trivalent element is doped, the F-center defect level is not occupied by electrons due to charge compensation. , The defect level is mainly derived from the Zr 4d orbital, and the localization of this defect-related state gradually decreases as δ in BaZrO 3−δ increases, but the modulation of the energy level is not significant for δ < 0.17 . Since the oxygen vacancy content in anhydrous BZY30 is δ = 0.15, the energy level of the localized state formed at the oxygen vacancy surrounded by Zr atoms does not depend on the dopant concentration in our case.…”

Section: Resultsmentioning

confidence: 99%

Determining the Atomic Arrangement near the Oxygen Vacancy in Yttrium-Doped Barium Zirconate by Photoluminescence Spectroscopy

et al. 2023

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Yttrium-doped barium zirconate is a solid electrolyte with several properties that are advantageous for fuel cells. We measure photoluminescence and photoluminescence excitation spectra of anhydrous yttrium-doped barium zirconate to characterize the atomic arrangement near the oxygen vacancy because the local structure is known to strongly influence the protonic conduction. The photoluminescence spectra of our anhydrous sintered pellets are composed of three components: recombination at the grain boundary region, recombination at a vacancy defect with an unpaired electron, and the transition of the electronic state of the oxygen vacancy. From the peak position of the latter photoluminescence component and the corresponding photoluminescence excitation spectrum, we can obtain information on the atomic arrangement that Zr is adjacent to the oxygen vacancies. This information is important for the design of materials with high protonic conductivity.

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“…There are many methods to synthesize Nano‐ZrO 2 with excellent properties, such as homogeneous precipitation, hydrothermal method, sol–gel method, micro‐emulsion, and oil‐water interface method . Compared with traditional methods, oil‐water interface method has many advantages like simple operation, low cost, and non‐toxic raw materials.…”

Section: Resultsmentioning

confidence: 99%

The gelation of hydroxypropyl guar gum by nano‐ZrO₂

Yang

et al. 2017

Polymers for Advanced Techs

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In the study, hydroxypropyl guar gum (HPG) gel is prepared by using Nano-ZrO 2 particles as the cross-linking agent. The Nan-ZrO 2 particles are prepared by using oil-water interface method. The physical properties such as morphology, particle size, and crystal structure of the Nano-ZrO 2 particles are analyzed by SEM, particle size analyzer, FT-IR, and XRD, respectively. The results show that the Nano-ZrO 2 particles are spherical particles with a little agglomeration; these spherical particles have a tetragonal structure and higher crystallinity, and the mean diameter of the first-level grain is 24 nm. The rheological properties including shear stress, complex modulus, elasticity modulus (G′), and viscosity modulus (G′′) of the Nano-ZrO 2 cross-linked HPG gel are investigated. The results show that the Nano-ZrO 2 cross-linked HPG gel is a pseudo-plastic non-Newtonian fluid with higher elastic modulus (G′ > G′′) and lower tanδ (tanδ < 1, the ratio of viscous and elastic modulus), which indicate that the Nano-ZrO 2 cross-linked HPG gel may have potential application in fracturing. KEYWORDSHPG gel, Nan-ZrO 2 particles, rheological properties | INTRODUCTIONHydroxypropyl guar gum (HPG) is not only the abundant green natural polymer in the world; it is also a kind of low-cost, renewable, environmentally friendly, and non-toxic material.1 In addition, HPG also has great mechanical property and good swelling capacity. Because of these advantages, HPG has aroused great concern in many applications, especially in oil and gas exploitation industry. However, in the process of fracturing flow-back, it is well known that these cross-linking ions still remain in the fracturing fluid, which has a serious impact on the reuse of fracturing fluid. As people pay more attention to the environment increasingly, the reuse of fracturing fluid is becoming a serious and urgent issue in oil field, and one of the most critical issues is to eliminate the influence of the remaining cross-linking agent. While the Nano-ZrO 2 cross-linked HPG gel is broken, nanoparticles can easily be eliminated by some simple means such as centrifugal separation and filtration, and the fracturing fluid can be used to reconfigure the fracturing gel, which not only protects the environment, but also improves the utilization efficiency of water resources.However, there are just few researches about physical nanoparticles used as a cross-linking agent in fracturing fluid.Some significant properties of zirconia, including the high temperature resistance, insulation, and shade resistance, have been widely studied. 5 However, the performance of cross-linking with HPG has not gained enough attention. Therefore, in this perspective, the objective of this paper is to synthetize a kind of zirconia with good dispersion in a convenient, cheap, and safe method and study on the crosslinking properties of Nano zirconia with HPG. For this purpose, the properties of the Nano-ZrO 2 are researched by SEM, XRD, FTIR, and particle size analysis. The viscoelastic property of the N...

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A first-principles investigation on the luminescence emissions of BaZrO3 obtained by microwave-assisted hydrothermal method

Cited by 4 publications

References 30 publications

Mechanism of photoluminescence in intrinsically disordered CaZrO3 crystals: First principles modeling of the excited electronic states

Mechanism of photoluminescence in intrinsically disordered CaZrO3 crystals: First principles modeling of the excited electronic states

Determining the Atomic Arrangement near the Oxygen Vacancy in Yttrium-Doped Barium Zirconate by Photoluminescence Spectroscopy

The gelation of hydroxypropyl guar gum by nano‐ZrO₂

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A first-principles investigation on the luminescence emissions of BaZrO3 obtained by microwave-assisted hydrothermal method

Cited by 4 publications

References 30 publications

Mechanism of photoluminescence in intrinsically disordered CaZrO3 crystals: First principles modeling of the excited electronic states

Mechanism of photoluminescence in intrinsically disordered CaZrO3 crystals: First principles modeling of the excited electronic states

Determining the Atomic Arrangement near the Oxygen Vacancy in Yttrium-Doped Barium Zirconate by Photoluminescence Spectroscopy

The gelation of hydroxypropyl guar gum by nano‐ZrO2

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The gelation of hydroxypropyl guar gum by nano‐ZrO₂