Grain boundary conductivity of yttria-doped zirconia: Influence of the microstructure and composite effect

Abstract

Abstract. Electrical conductivity measurements have been performed on yttrium-doped zirconia and on YSZ-alumina composites sintered from powders prepared by conventional techniques (commercial powder) or by freeze-drying. The results have been analyzed taking into account the microstructure of the interfaces which were characterized by electron microscopy. The samples sintered from freeze-dried powders show the highest conductivity values and this conductivity decreases in the presence of alumina. The microstructure of these polycrystals is clean, homogeneous with lens-shaped glassy pockets at triple-points and there is no evidence for continuous boundary films. Contrary, the samples prepared and sintered from commercial powders show a poor microstructure and the presence of a glassy film in a large number of grain boundaries. Furthermore, alumina leads to an increase in conductivity, which reaches a maximum at around 2 mol-% alumina. This result may be attributed to the influence of alumina on the viscosity and wetability of the glassy phase. However, all samples show the same grain boundary activation energy. This confirms that the transport mechanism is the same in all cases and that only clean grain boundaries contribute to the transport processes.

Ionic conductivity and activation energy for oxygen ion transport in superlattices — The multilayer system CSZ (ZrO2+CaO)/Al2O3

“…in LiI/Al 2 O 3 as one of the prototype materials [1]. In recent years this heterogeneous doping was intensively studied because of the great interest in the increase of ionic conductivity at low temperatures [2][3][4][5][6][7][8][9][10].…”

The effect of alumina addition on the electrical conductivity of Gd-doped ceria

“…[15][16][17][18]. In this study, we studied the effect of alumina addition on the electrical conductivity and the mechanical properties of ceria.…”

Effect of alumina additions on the anode|electrolyte interface in solid oxide fuel cells

“…Arrhenius plot of grain-boundary and total conductivity of 15A10YSZ and 15A10YSZ NiAl 2 O 4 . [9]. The activation energies of 15A10YSZ and 15A10YSZ/NiAl 2 O 4 are the same within experimental error.…”

“…Due to the higher activation of the grain boundaries, at high temperatures the grain-boundary conductivity increases faster than the bulk conductivity, which has a lower activation energy at high temperature (≥600 • C) [9,20,21]. Therefore, at high operating temperatures, the grainboundary contribution to the total resistivity diminishes.…”

“…At 700 • C, there is no difference in the total conductivities. Previous authors [9,20,21] have reported that the bulk activation energy of YSZ is characterised by two regions, viz., a low-temperature (300-500 • C) and a high-temperature (600-800 • C) region. At high temperature, the bulk activation energy decreases, but the grain-boundary activation energy remains unaffected.…”