In-situ measurements by impedance spectroscopy of highly resistive α-alumina

Flash sintering of alumina: Effect of different operating conditions on densification

“…EIS, interfacial polarization) fixing the energy barrier for Al and O self-diffusion in the range 0.8-2.4 eV [29,34,43,48]. Such values are in agreement with those found in this study and perfectly match with those (0.7 and 2.5 eV) obtained by theoretical calculation [26,27,49,50].…”

“…The activation energy was estimated as 1.2 ± 0.2, 1.2 ± 0.1, 1.0 ± 0.2 eV for platinum, carbon and silver electrodes, respectively. Similar results were found by Cologna et al [34] who worked with dense alumina bodies. The calculated activation energies are far lower than the band gap for pure corundum (8.7-10.8 eV) [36][37][38][39].…”

In-situ Impedence Spectroscopy Study of Electrical Conductivity and Ionic Transport in Thermally Grown Oxide Scales on a Commercial FeCrAl Alloy

“…3, where the impedance data are plotted as -Z 00 vs. Z 0 . In this case, essentially only one semicircle is seen from the plots, which is similar to that of sintered polycrystalline and single-crystalline a-alumina [24,27]. The ''depressed'' appearance of the semicircle is due to the fact that the alumina scale does not behave as a perfect dielectric, unlike pure a-alumina.…”

“…The reason for the low t i value obtained in this work is not straightforward. The effect of surface conduction [24] was investigated, but that measurement showed the same low t i on a similar sample (data unpublished). Leakage currents due to poor insulation of the sample holder could be a source of error.…”

“…Before the measurement the sample was mounted into an electrically shielded sample holder, which was then inserted into a tube furnace. Details of the setup has been described earlier [24]. The measurements were performed in lab air, using the same electrode configuration as for the measurement of t i , shown in Fig.…”