Optical and dielectric behaviors of alumina after an electromagnetic irradiation

Vallayer, J.; Jardin, C.; Tréheux, D.

doi:10.1016/s0925-3467(00)00093-8

Cited by 19 publications

(13 citation statements)

References 8 publications

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“…According to the image charge theory, this could partially explain why the adhesion contribution to the friction coefficient decreases, when the annealing temperature increases. In a similar way, the UV irradiation leads to a transfer of electrons from O-vacancies to Al-vacancies [46]. As a consequence, more O-vacancies become able to trap electrons and the number of trapped electrons (generated during friction) becomes higher than for non-irradiated sample, leading to a higher contribution of the adhesion to the friction coefficient.…”

Section: Discussionmentioning

confidence: 95%

“…Indeed, it appears that the ability for sapphire to trap charges decreases with the annealing temperature and in contrast, increases with the UV irradiation. The cathodoluminescence study [46] of these samples has allowed us to propose an explanation of the trapping results as a function of the electronic configuration and the number of point defects in sapphire such as oxygen and aluminium vacancies. …”

Section: Semm Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Electrical charges and tribology of insulating materials

Guerret‐Piécourt¹,

Bec²,

Tréheux³

2001

Comptes Rendus de l'Académie des Sciences - Series IV - Physics

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Résumé. La description de la génération de charges électriques lors du contact entre isolants a été faite de longue date. En revanche, la prise en compte quantitative des effets de ces charges est rarement évoquée dans les bilans énergétiques concernant les problèmes de frottement. En nous appuyant sur des résultats publiés et sur nos propres expérimentations sur le piégeage des charges dans les isolants, nous montrons l'importance de l'action de ces charges électriques sur l'énergie d'interaction pendant le frottement. Enfin, nous proposons d'évaluer quantitativement cette contribution grâce à l'utilisation complémentaire de la méthode « miroir » et de mesures de forces de surfaces. caractérisation diélectrique / frottement / triboélectrification / interactions interfaciales / énergie libre de surface / charge d'espace / forces de surface Abstract. Electrical charges generation occurring during contact and friction of insulating materials has been identified for a long time. However the contribution of these electrical charges to the friction behaviour is usually neglected in the energetical balances. Based on published results and on our own experimental results on the ability of the dielectric materials to trap charges, we show in this study that the interaction energy during friction depends markedly on these trapped charges. Eventually, we propose the complementary use of the "mirror " method and of surface forces measurements to obtain a quantitative evaluation of this contribution. dielectric behaviour / friction / triboelectrification / interfacial interactions / surface free energy / space charge / surface forces IntroductionSurface forces act between two surfaces when they are in close proximity. They are very well known in the field of colloid science [1, 2] and they have also a strong impact in other fields like adhesion, wetting or friction. Resulting from very complex phenomena, these forces include mechanical, physico-chemical and electrical effects. This paper is focused on one phenomenon which is often neglected : the effects of electrical charges trapped in the near surface or in the bulk of dielectric materials (ceramics, polymers...). In section 2, the various types of surface forces according to their range are recalled. Then, it is shown that some published results in the friction and adhesion domains suggest the major role of these electrical charges. This is followed by an overview on charge generation and trapping during contact or friction in section 3. Our own results are used in section 4 to discuss how electrical charges can influence the friction behaviour of dielectrics. In order to go further, the complementary use of the "mirror " method and of surface forces measurements is proposed in the aim to obtain a quantitative evaluation of this contribution.

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Section: Discussionmentioning

confidence: 95%

Section: Semm Resultsmentioning

confidence: 99%

Electrical charges and tribology of insulating materials

Guerret‐Piécourt¹,

Bec²,

Tréheux³

2001

Comptes Rendus de l'Académie des Sciences - Series IV - Physics

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“…The presence of these impurities in nominally pure samples is a fairly common feature for Al 2 O 3 . 2,[26][27][28] The luminescence band at 510 nm observed in anion-deficient Al 2 O 3 has been attributed to donor centers like interstitial aluminum ions 29 and this assignment prevailed for long. 5,27 However the authors of Ref.…”

Section: -2mentioning

confidence: 99%

Studies of concentration dependences in the luminescence of Ti-doped Al2O3

Mikhailik

Stefano

Henry

et al. 2011

Journal of Applied Physics

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The variation of luminescence and excitation spectra of titanium doped Al 2 O 3 for the concentration of Ti ranging from 10 to 1000 ppm was investigated using synchrotron radiation. In the lightly doped Al 2 O 3 -Ti (<100 ppm) samples we identified several emission bands. These are the emission of the excitons localized at Ti (290 nm), the emission due to F þ centers (325 nm), the band around 420 nm traditionally attributed to F center emission, and the luminescence of Ti 3þ ions at 720 nm. The emphasis in this study is on the clarification of the nature of the blue emission band in the samples with high concentration of Ti (!100 ppm), where the luminescence and excitation spectra of the blue emission exhibit noticeable variability. This is explained by a model of the luminescence process of Ti 4þ -F centers that includes the photoionization of Ti 3þ , the subsequent capture of electrons at F þ -centers, formation of excited F-centers and, finally, the emission of a blue photon. The quenching of the blue emission with increasing Ti concentration is interpreted in terms of competition between oxygen vacancies and Ti 4þ centers in the capture of the electron.

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“…Especially, the oxygen-related defects in single-crystalline sapphire are known to appear as the luminescence centers called F + and F centers when the oxygen vacancies are differently charged with electrons. In order to investigate optical properties and behaviors of the oxygen-vacancy-related defects and other deep luminescence centers, a number of studies on luminescence of synthetic sapphire have been performed using particle beam [3] and electron beam [4,5] although such probing particles often modify the electronic states of the target sapphire. By contrast, few studies on natural sapphire including diffusion-treated one have been done until now.…”

Section: Introductionmentioning

confidence: 99%