Single and couple doping ZnO nanocrystals characterized by positron techniques

Pasang, T.; Namratha, K.; Guagliardo, Paul; Byrappa, K.; Ranganathaiah, Chikkakuntappa; Samarin, Sergey; Williams, James

doi:10.1088/2053-1591/2/4/045502

Cited by 6 publications

(9 citation statements)

References 44 publications

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“…Figure depicts the ratio curves of EMD in the A-A600 samples to that of pure single-crystal silicon, which was used for reference. All the peaks appear around an electron momentum of P L ∼ 14 × 10 –3 m o C associated with the positron annihilation by 2p electrons of O . This result suggested that some monovacancies of Mn were likely formed in all samples.…”

Section: Resultssupporting

confidence: 82%

“…A shoulder-like peak appearing in the range of P L ∼ 15–19 × 10 –3 m o C, a characteristic of the positron annihilation by 3d electrons of Mn, was observed for the A sample only. The appearance of this shoulder-like peak indicated the possible existence of O vacancies in this A sample, similar to that reported for ZnO materials . To sum up, the as-prepared A sample should contain both vacancies of Mn and O, whereas other samples, namely A200, A400, and A600, mostly contained monovacancies of Mn.…”

Section: Resultsmentioning

confidence: 78%

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Crystallization Pathways and Evolution of Morphologies and Structural Defects of α-MnO₂ under Air Annealing

et al. 2022

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Manganese dioxide nanomaterials have wide applications in many areas from catalysis and Li−ion batteries to gas sensing. Understanding the crystallization pathways, morphologies, and formation of defects in their structure is particularly important but still a challenging issue. Herein, we employed an arsenal of X-ray diffraction (XRD), scanning electron microscopy (SEM), neutron diffraction, positron annihilation spectroscopies, and ab initio calculations to investigate the evolution of the morphology and structure of α-MnO 2 nanomaterials prepared via reduction of KMnO 4 solution with C 2 H 5 OH prior to being annealed in air at 200−600 °C. We explored a novel evolution that α-MnO 2 nucleation can be formed even at room temperature and gradually developed to α-MnO 2 nanorods at above 500 °C. We also found the existence of H + or K + ions in the [1 × 1] tunnels of α-MnO 2 and observed the simultaneous presence of Mn and O vacancies in α-MnO 2 crystals at low temperatures. Increasing the temperature removed these O vacancies, leaving only the Mn vacancies in the samples.

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Section: Resultssupporting

confidence: 82%

Section: Resultsmentioning

confidence: 78%

Crystallization Pathways and Evolution of Morphologies and Structural Defects of α-MnO₂ under Air Annealing

et al. 2022

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“…A shoulder-like peak appearing in the range of 15 -19 x 10 -3 m0c, which describes the positron annihilation by 3d electrons of Mn, is seen for the A sample only. The appearance of this shoulder-like peak indicates a possible existence of O vacancies in the A sample, similar to that reported for ZnO materials 33 (above 400 o C), which cannot be explored by either XRD and/or ND measurements.…”

Section: Xrd Analysis Xrd Spectra Presented Insupporting

confidence: 64%

“…In this DB measurement, two parameters S and W are often used to describe the quanta resulting from positron annihilation with valence and core electrons, respectively 40 . Here, S is determined by the ratio of the area under the center of annihilation peak to the total peak area, whereas W is calculated based on the ratio of the areas under the wing regions on both sides of annihilation peak to the total peak area 33 . The longitudinal electron momentum can be converted from DB spectra.…”

Section: Bet and Bjh Analysesmentioning

confidence: 99%

“…It is well-known that the electron momentum has a close relation with positron annihilation sites, which can be used to determine the types of defect and information about surrounding atoms. In this analysis, the EMD is obtained based on the ratio of the normalized spectra of the samples to the normalized spectrum of a standard single-crystal silicon used for reference 33,38 .…”

Section: Bet and Bjh Analysesmentioning

confidence: 99%

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Crystallization pathways, morphologies and structural defects of α-MnO2 nanomaterial synthesized under annealed temperatures

Dinh¹,

Luu²,

Siemek³

et al. 2020

Preprint

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Manganese dioxide, in particular α-MnO2, is one of the advanced inorganic nanomaterials having wide applications in many areas. Hence, understanding the crystallization pathways, morphologies, and formation mechanism of defects in its structure is of particular importance, not only for fundamental science but also for practical applications. Herein, different physically and chemically based methods, such as Neutron Diffraction (ND), XRD, SEM, TPR- H2, TGA-DSC, FT-IR, Positron Annihilation Lifetime (PAL), Doppler Broadening (DB) of positron annihilation radiation, and Electron-Momentum Distribution (EMD) measurements combined with theoretical calculations, were utilized to systematically investigate the composition, structure, and morphology of α-MnO2 nanomaterial under different annealed temperatures. The investigated material was synthesized at room temperature using a facile chemical method with potassium permanganate (KMnO4) and ethanol (C2H5OH), prior to being treated by temperatures of 100 oC – 800 oC. Results demonstrated, for the first time, that the α-MnO2 nucleation can be formed even at room temperature and gradually developed to α-MnO2 nanorods at 600 oC. This novel finding, which cannot be explored by conventional XRD, was confirmed by ND analysis. In addition, PAL analysis combined with theoretical ab initio calculations indicated the existence of H+ ions in the tunnel [1x1] of α-MnO2. At the same time, DB and EMD measurements explored the presence of Mn and O vacancies in α-MnO2 crystals at low temperatures. Finally, the present study reported a remarkable finding that organic molecules may act as reactants as well as templates, which are entirely decomposed and disappeared at highly annealed temperatures.

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Positron annihilation in Eu-, Ag-, Er-, and Pr-doped ZnAl2O4 studied by modified coincidence Doppler broadening spectroscopy

Ghamari,

Imani,

Ghasemifard

2024

Indian J Phys

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Single and couple doping ZnO nanocrystals characterized by positron techniques

Cited by 6 publications

References 44 publications

Crystallization Pathways and Evolution of Morphologies and Structural Defects of α-MnO₂ under Air Annealing

Crystallization Pathways and Evolution of Morphologies and Structural Defects of α-MnO₂ under Air Annealing

Crystallization pathways, morphologies and structural defects of α-MnO2 nanomaterial synthesized under annealed temperatures

Positron annihilation in Eu-, Ag-, Er-, and Pr-doped ZnAl2O4 studied by modified coincidence Doppler broadening spectroscopy

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Single and couple doping ZnO nanocrystals characterized by positron techniques

Cited by 6 publications

References 44 publications

Crystallization Pathways and Evolution of Morphologies and Structural Defects of α-MnO2 under Air Annealing

Crystallization Pathways and Evolution of Morphologies and Structural Defects of α-MnO2 under Air Annealing

Crystallization pathways, morphologies and structural defects of α-MnO2 nanomaterial synthesized under annealed temperatures

Positron annihilation in Eu-, Ag-, Er-, and Pr-doped ZnAl2O4 studied by modified coincidence Doppler broadening spectroscopy

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Crystallization Pathways and Evolution of Morphologies and Structural Defects of α-MnO₂ under Air Annealing

Crystallization Pathways and Evolution of Morphologies and Structural Defects of α-MnO₂ under Air Annealing