Mixed conductivity of gadolinium titanate-based pyrochlore ceramics: The grain boundary effects |
| |
Authors: | V V Kharton F M B Marques E V Tsipis A P Viskup M V Patrakeev A V Harkavy R Samigullina J R Frade |
| |
Institution: | (1) Department of Ceramics and Glass Engineering, CICECO, University of Aveiro, 3810-193 Aveiro, Portugal;(2) Institute of Physicochemical Problems, Belarus State University, 14 Leningradskaya Str., 220080 Minsk, Belarus;(3) Institute of Solid State Chemistry, 91 Pervomaiskaya Str., 620219 Ekaterinburg, Russia |
| |
Abstract: | In order to reveal the role of grain boundaries on the ionic and electronic conduction processes, the transport properties
of Gd2−xGaxTi2O7−δ (x=0.10–0.14) pyrochlore ceramics, pure and with SiO2 additions, were studied at 700–950 °C by impedance spectroscopy and faradaic efficiency measurements. The oxygen ion transference
numbers of “pure” materials in air vary in the range of 0.95–0.97, increasing when temperature decreases. For silica-containing
ceramics having, as expected, highly resistive grain boundaries, the ion transference numbers were considerably lower, 0.76–0.88,
and increase with temperature. This behavior suggests that grain boundaries in these oxygen ion-conducting ceramics have a
larger limiting effect on ionic transport than on electronic conduction. Increasing boundary resistivity may increase the
relative role of electronic conductivity in solid oxide electrolytes, thus preventing their potential use in electrochemical
cells at low temperatures. Also, the presence of even small electronic contributions to the total conductivity may lead to
significant errors in the grain-boundary resistance values estimated from impedance spectroscopy data. The evaluation of the
grain boundary exact contribution should be based on a clear knowledge of the magnitude of transference numbers.
Paper prestented at the 9th EuroConference on Ionics, Ixia, Rhodes, Greece, Sept. 15 – 21, 2002. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|