Dynamic investigation of charging kinetics in sintered yttria stabilized zirconia and alpha-alumina polycrystalline ceramics under electron beam irradiation

International audienceA synthesis of work in various research fields shows that (i) the microscopic damage processes in insulating materials under stress (electrical, mechanical, thermal or radiation) are not yet understood but are indisputably related to energy localization on defects. The nature of these defects is still debated but it is acquired that their annihilation is exothermic, (ii) by trapping of charges one localizes a mechanical energy which is relaxed after detrapping, (iii) the charge injection and the dielectrics characterization by electron beam techniques are particularly suited to the damage process study.In the scanning electron microscope chamber, an adapted sample holder measured separately the influence and conduction currents in order to study the charge dynamic during irradiation and discharge dynamic after irradiation of insulating materials. The studied materials are polycrystalline alpha-alumina and yttria stabilized zirconia, characterized by their grain sizes, respectively of 2.5 mu m and 300 nm, their mechanical fracture stress, respectively of 400 MPa and 96 MPa, their electric conductivity, respectively of 10(-14) S/m and 10(-8) S/m and their electrical breakdown field, respectively of 21.2 MV/m and 18.2 MV/m. Interestingly, it was observed that the charging and discharging dynamics of these two materials are quite different. At room temperature, the electrons are trapped in a very stable manner by alpha-alumina and are labile in yttria stabilized zirconia. This difference in stability can be (i) the result of electronic structure differences of both materials, and (ii) the internal stresses effect in the grain boundaries where the oxygen vacancies concentration greatly increases the Debye-Waller factor. This is consistent with the fact that the electron-phonon interactions are at the heart of the damage process. Studies are ongoing to develop characterization techniques to guide the materials manufacture by optimizing their internal stresses

Grains Size Effect on Charge Trapping in Electron Irradiated Ceramics; Stability and Discharge Study Using a Special Arrangement in a Scanning Electron Microscope

International audienceDielectric breakdown of ceramics is obviously an important failure in the levels of equipment requiring some insulation safety or to ensure their proper functioning. The manifested microscopic damage processes under electrical stress are indisputably related to charge trapping and detrapping and thus related to energy localization on defects. This work enabled the development of a technique (Influence Current Method) using a specific arrangement in a Scanning Electron Microscope chamber, allowing to measure separately and simultaneously the influence and conduction currents. This permits subsequently tracing back to the trapped charge dynamic during and after electron irradiation. The purpose of this paper is to study firstly the stability of trapped charge in ZrO2/Y2O3 ceramic and secondly to investigate the grains size effect on charging and discharging processes. Via this results the microstructure - dielectric strength correlations are well justified. Instability of trapped charge was found; the majority was evacuated from the irradiated volume. This entrusts to it a conductive insulator character. It has been found that more the grains size decreases more the amount of stabilized trapped charge decreases. This is due to the eventual increase in the grains boundary density in which the oxygen vacancies are concentrated. Note that the increase of grains size improves the dielectric strength

Charge injection modeling and initial SE yield by two fluxes method; New source term of secondary electron generation by Monte Carlo simulation

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Cranial Metastatic Alveolar Rhabdomyosarcoma Mimicking Hematological Malignancy In An Adolescent Boy

Widespread alveolar rhabdomyosarcoma (ARMS) with bone marrow involvement and with an unknown primary tumor, especially presenting with acute tumor lysis syndrome can be easily misdiagnosed as a hematological malignancy. Furthermore, brain metastasis of ARMS is rare seen in children. Herein, we report a 14-year-old boy presenting with acute tumor lysis syndrome due to bone marrow invasion of ARMS, who was diagnosed after abdominal paraaortic lymph node biopsy. Despite radiological and nuclear medicine imaging, the primary tumor site could not be found. He was treated with vincristine, topotecan, and cyclophosphamide for 42 weeks. Six months after the completion of treatment, he suffered from severe headache, blurred vision, right hemiplegia, and severe bone pain. Cranial magnetic resonance imaging showed multiple hemorrhagic infarctions. Brain biopsy showed brain metastasis with PAX3-FKHR fusion transcript. The clinicians must be vigilant about solely brain metastasis in ARMS without additional metastasis.WoSScopu