Electron-irradiation-induced phase segregation in crystalline and amorphous apatite; a TEM study

Other| October 01, 1997 Electron-irradiation-induced phase segregation in crystalline and amorphous apatite; a TEM study A. Meldrum; A. Meldrum University of New Mexico, Department of Earth and Planetary Sciences, Albuquerque, NM, United States Search for other works by this author on: GSW Google Scholar L. M. Wang; L. M. Wang Search for other works by this author on: GSW Google Scholar R. C. Ewing R. C. Ewing Search for other works by this author on: GSW Google Scholar American Mineralogist (1997) 82 (9-10): 858–869. https://doi.org/10.2138/am-1997-9-1003 Article history first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation A. Meldrum, L. M. Wang, R. C. Ewing; Electron-irradiation-induced phase segregation in crystalline and amorphous apatite; a TEM study. American Mineralogist 1997;; 82 (9-10): 858–869. doi: https://doi.org/10.2138/am-1997-9-1003 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search nav search search input Search input auto suggest search filter All ContentBy SocietyAmerican Mineralogist Search Advanced Search Abstract Single crystals of natural F-rich apatite and 800 keV Kr2+ ion-beam–amorphized apatite were irradiated by an electron beam in a transmission electron microscope over a range of beam energies and beam currents. Irradiation of crystalline apatite using a high current density (16 A/cm2) caused the precipitation of cubic CaO from the crystalline apatite matrix. Using a lower beam current (1.6 A/cm2), the formation of nanometer-sized voids was observed, but CaO did not crystallize even after prolonged irradiation. Amorphous apatite crystallized to a coarse-grained polycrystalline assemblage of apatite crystallites at 85–200 keV. Increasing the beam current through the sample caused the formation of finegrained cubic CaO, and the crystallization of apatite was not observed, even at high doses. In each case, many beam-induced bubbles formed and were typically larger at the edge of the beam. Thermal annealing at 450 °C resulted in epitaxial crystallization from the thick portions of the TEM foil and resulted in a single crystal with a high defect density. Electron-beam irradiations at 300 °C confirmed that the difference in microstructural evolution as a function of current density is driven by dose-rate effects. In fact, temperature and dose rate are competing effects in the precipitation of CaO. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not currently have access to this article.