Characterization of densified fully stabilized nanometric zirconia by positron annihilation spectroscopy

Garay, Javier E.; Glade, S. C.; Asoka‐Kumar, P.; Anselmi‐Tamburini, Umberto; Munir, Zuhair A.

doi:10.1063/1.2163016

Cited by 23 publications

(19 citation statements)

References 29 publications

(38 reference statements)

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“…However, they showed that the peak position is at about 11.5 3 10 23 m o C which is lower compared with our data. This attributed to difference reference CDBAR spectrum, Si instead of pure PVC and/or change grain size of the sample used as clear from the data of Dutta et al 39 and Garay et al 40 The ratio curves for doped samples [ Fig. 1(B)] decrease up to 2.0 3 10 23 m o C, showing a dip in the There is a linear correlation between the height of the high momentum region and the Al 2 O 3 concentration as shown in Figure 2.…”

Section: Resultsmentioning

confidence: 92%

Coincidence Doppler broadening spectroscopy in polyvinyl chloride after doping with Al₂O₃

Hamed

2008

J of Applied Polymer Sci

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Coincidence Doppler broadening of annihilation radiation (CDBAR) and Vickers hardness techniques were performed to study pure Al 2 O 3 , pure polyvinyl chloride (PVC), and doped PVC with different concentrations of Al 2 O 3 (10-50%). The CDBAR ratio curves with respect to pure PVC were presented and reflect the momentum distribution of all the samples. The peak around 14.5 3 1023 m o C in the CDBAR ratio curves suggests a large contribution of positron annihilation with the Al 2 O 3 . There is a linear correlation between the height of this peak and the Al 2 O 3 concentration. The S-and W-parameters were extracted from the CDBAR spectra and increase with increasing the Al 2 O 3 concentration showing discontinuity at 30% of Al 2 O 3 concentration on PVC. The present data confirmed that there is no positronium formation in pure Al 2 O 3 as a result of smaller S-parameter. The Vickers hardness increases with increasing the Al 2 O 3 concentration in PVC showing a linear dependence with two different slopes depend on the Al 2 O 3 concentration range. A correlation between the Vickers hardness (macroscopic data) and the W-parameter (microscopic data) was observed.

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Section: Resultsmentioning

confidence: 92%

Coincidence Doppler broadening spectroscopy in polyvinyl chloride after doping with Al₂O₃

Hamed

2008

J of Applied Polymer Sci

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“…In Ref. [3] the two components arise mainly from the annihilation of positrons inside nanograins, authors [4,5] related these components to the GB's. In our paper [6], the latter interpretation was further supported by the observed I 2 : I 1 ratios vs. the mean grain size.…”

Section: Resultsmentioning

confidence: 99%

“…Such a situation is a challenge for positron annihilation spectroscopy (PAS). Despite of several earlier PAS investigations [2][3][4][5], there is still a lack of unambiguous explanation of PAS data on YSZ materials.…”

Section: Introductionmentioning

confidence: 99%

Positron Lifetimes in Zirconia-Based Nanomaterials

et al. 2008

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Positron lifetime spectroscopy is employed in a comparative study of several zirconia-based materials: (i) the pressure-compacted nanopowders of the three zirconia polymorphs -pure ZrO2 (monoclinic), yttria-stabilized ZrO 2 +3 mol.% Y 2 O 3 (tetragonal) and yttria-stabilized ZrO 2 +8 mol.% Y 2 O 3 (cubic), (ii) ceramic materials obtained by sintering of the above two yttriastabilized zirconia nanopowders and (iii) the tetragonal and cubic yttria--stabilized zirconia monocrystals. Positron lifetime data observed on the nanopowders suggest that the two shortest components, exhibiting lifetimes of ≈ 180 and ≈ 370 ps, arise from the annihilation of positrons trapped in defects associated with grain boundaries, presumably the vacancy-like defects and tripple points, respectively. Positron lifetime spectra observed on the ceramic materials resemble those found for the corresponding monocrystals, giving thus an additional support to the above interpretation of the nanopowders results.

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“…This interpretation was used in several other works on YSZ [4][5][6], but the value of the positron lifetime that should be associated with such a complex is still under question. It should be mentioned that in [3,4] sintered powders of c-YSZ were investigated and spectra with at least two-components were obtained with mean lifetimes in the range 214-248 ps [3] and 193 ps [4].…”

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confidence: 90%

“…Contrary, Garay et al [6] argue that the negatively-charged grain-boundary space regions act as positron trapping centres. Trapping at the grain-boundaries is also found in our measurement on YSZ powders [7].…”

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confidence: 94%

Positron annihilation in three zirconia polymorphs

Melikhova

Kuriplach

Čı́žek

et al. 2007

Phys. Status Solidi (c)

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Positron lifetimes and high momentum profiles both for the perfect lattice and selected defects are calculated in three (cubic, tetragonal and monoclinic) zirconia polymorphs using the atomic superposition method. Theoretical data are compared with the measured positron lifetime for cubic and tetragonal monocrystals of yttria-stabilized zirconia (YSZ) and coincidence Doppler broadening measurements on tetragonal monocrystals of YSZ. Positron lifetime spectra of YSZ monocrystals exhibit a single component spectrum with lifetimes 178 ps and 174 ps for cubic and tetragonal phases, respectively. Possible interpretations of measured lifetime and Doppler data are discussed.1 Introduction Zirconia (ZrO 2 ) based materials are promising for many practical applications, including heat-resistant structural and functional ceramics, solid oxide fuel cells and oxygen sensors, as well as applications in nuclear fuel and waste confinement. Positron annihilation may bring important information on defects in this class of materials, which is a substantial prerequisite for understanding zirconia properties in general.At room temperature pure ZrO 2 exhibits the monoclinic baddelyite structure (m-ZrO 2 , space group c P 1 2 [1]) with the Zr 4+ ion in a distorted seven-fold coordination. On increasing the temperature, the structure transforms into a tetragonally distorted fluorite structure (t-ZrO 2 , nmc P 2 4[1]) at T ~ 1370 K, with Zr 4+ surrounded by eight anions, but with two slightly different Zr 4+ -O 2-distances. Perfect eightfold coordination is achieved at T ~ 2643 K with a transformation to a cubic fluorite structured phase (cZrO 2 , m Fm3 [1]), followed by melting at T ~ 2988 K. High-temperature c-ZrO 2 and t-ZrO 2 structures can be stabilized at room temperature by an addition of yttrium oxide (Y 2 O 3 ). These so-called "yttria- Obviously, positron annihilation spectroscopy (PAS) has a high potential for the investigation of defects in YSZ. However, the assignment of experimental results to corresponding defect configurations is still on the level of hypotheses without direct and convincing confirmation. Dominant positron trapping sites in YSZ are supposed to be associated with complexes (

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Characterization of densified fully stabilized nanometric zirconia by positron annihilation spectroscopy

Cited by 23 publications

References 29 publications

Coincidence Doppler broadening spectroscopy in polyvinyl chloride after doping with Al₂O₃

Coincidence Doppler broadening spectroscopy in polyvinyl chloride after doping with Al₂O₃

Positron Lifetimes in Zirconia-Based Nanomaterials

Positron annihilation in three zirconia polymorphs

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Characterization of densified fully stabilized nanometric zirconia by positron annihilation spectroscopy

Cited by 23 publications

References 29 publications

Coincidence Doppler broadening spectroscopy in polyvinyl chloride after doping with Al2O3

Coincidence Doppler broadening spectroscopy in polyvinyl chloride after doping with Al2O3

Positron Lifetimes in Zirconia-Based Nanomaterials

Positron annihilation in three zirconia polymorphs

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Coincidence Doppler broadening spectroscopy in polyvinyl chloride after doping with Al₂O₃

Coincidence Doppler broadening spectroscopy in polyvinyl chloride after doping with Al₂O₃