Electromigration and charge carrier density versus free lattice volume effects in doped zirconia ceramics

Abstract

Ion conducting yttria-stabilized tetragonal zirconia (3YTZ) and Er 3+ -, Nd 3+-and Hf 4+ -doped 3YTZ ceramics were prepared and studied in this work. It is noted that dopant-induced structural effects, associated with free lattice volume for bulk conduction, may still be dominant over charge carrier density effects, even for variations of these latter by up to about 30%. In that way, dopant ion size-modified charge (oxygen vacancy) mobility varied to about +25% in Er 3+ -doped 3YTZ and about −45% in Nd 3+ -doped 3YTZ, with respect to original 3YTZ. Meanwhile, the behavior of grain-boundary electrical properties appeared to adapt well with Frenkel's space-charge model. In both bulk and grain-boundary cases, the electrical response of Hf 4+ -doped 3YTZ remained close to that from 3YTZ, a fact which is also discussed in this report.

Impedance Spectroscopy and Dielectric Properties of Flash Versus Conventionally Sintered Yttria‐Doped Zirconia Electroceramics Viewed at the Microstructural Level

“…The activation energy for the grain‐boundary conductivity is slightly higher than for the bulk, which might arise from the semi‐blocking nature of the grain boundaries. All the values are consistent with the activation energy for the transport of oxygen vacancies ( V ö) in zirconia‐based and parent compounds, whose value remains around 1.0 eV …”

“…During the above functions, the electrolyte is subjected to electric fields or differential to drive ion transport. However, the kinetics of charge migration may become limited by internal interfaces (e.g., grain boundaries) which can behave as blocking or semi‐blocking regions in polycrystalline materials . Control of the microstructure is then a key point in the processing of these materials in order to obtain high sensitivity and performance of such charge transport‐based devices.…”

Evidence of fluoride oxidation for development of the electrochemically-induced crystallization observed in lead oxyfluoroborate glasses

“…Fitting of the data in Fig. 1b through applying relation (3) provided activation energies of about 0.64 ± 0.04 to 0.91 ± 0.05 eV from pure PbF 2 to pure YSZ, in good agreement with literature [4,20,21], while noting parallely that the material conductivity correspondingly decreases from the former compound (with fluoride ions acting as leading charge carriers [20]) to the latter one (with oxygen vacancies acting as leading charge carriers [21,22]). For the data collected at 200°C, the composition dependence of bulk conductivity from all the prepared composite-like samples is illustrated in Fig.…”

A Huge Effect of Weak dc Electrical Fields on Grain Growth in Zirconia

“…The reviewer of this manuscript has pointed out that electrical fields have been known to influence microstructure evolution in ways other than described here. Examples include electromigra- tion, 17 and the possibility of precipitating oxygen-filled pores at grain boundaries due to electrolysis in fuel cells. 18 We did not observe any unusual changes in the microstructure such as these.…”