Self-diffusion activation energies in alpha-Al2O3 below 1000 degrees C: measurements and molecular dynamics calculation
2004 (English)In: Philosophical Magazine Letters, ISSN 0950-0839, E-ISSN 1362-3036, Vol. 84, no 12, 781-789 p.Article in journal (Refereed) Published
Results from impedance spectroscopy measurements at temperatures between 400 and 1000&DEG; C, for single crystal and highly pure and dense polycrystalline α-Al2O3 samples with well-defined grain size, are compared with that from molecular dynamics calculation. Between 650 and 1000&DEG; C, the measured activation energy for conductivity is 1.5 eV for the single crystal, and increases from 1.6 to 2.4 eV as the grain size decreases from 15 to 0.5 μ m. The molecular dynamics calculation leads to the conclusion that the self-diffusion activation energy is about 1.5 eV for O and 1.0 eV for Al in single crystal α-Al2O3. The much higher mobility of O ions makes the O ions responsible for the conductivity of the single crystal oxide. It seems that the grain boundary leads to an increase in the activation energy. However, the quantitative influence of grain boundary still needs to be explained. Between 400 and 650&DEG; C, the measured activation energy is about 1.0 eV and independent of the grain size.
Place, publisher, year, edition, pages
2004. Vol. 84, no 12, 781-789 p.
Activation energy; Crystal growth from melt; Diffusion; Electric conductivity; Grain boundaries; Grain size and shape; Molecular dynamics; Polycrystalline materials; Single crystals; Spectroscopic analysis; Thermal effects; Impedance spectroscopy; Molecular dynamics calculation; Self-diffusion activation energy; Single crystal oxides; Alumina
IdentifiersURN: urn:nbn:se:kth:diva-6901DOI: 10.1080/09500830500071051ISI: 000228882900004ScopusID: 2-s2.0-19944413992OAI: oai:DiVA.org:kth-6901DiVA: diva2:11745
QC 201008262007-03-152007-03-152010-08-26Bibliographically approved