Role of the microstructure on the transport properties of Y-doped zirconia and Gd-doped ceria

Abstract

Abstract. Transmission electron microscopy characterizations and XPS analyses have allowed usto show the influence of the microstructure and nanochemistry on the transport properties of Y203-(9 mol%)-stabilized zirconia (YSZ) and Gd203 (10 mol%)-doped ceria (GDC). The grain boundary electrical conductivity (~gb) and oxygen diffusion coefficient (Do) of conventional YSZ ceramics increase with the grain size, while an opposite behavior was found for GDC samples. This difference was attributed to glassy precipitates present at YSZ grain boundaries. Furthermore, it was shown that kinetic demixing processes take place during cooling, at the end of sintering. This causes important changes in the cationic species distribution at interfaces and plays an important role on the transport properties of these two materials.

Defect thermodynamic and transport properties of nanocrystalline Gd-doped ceria

“…The electrical conductivity was characterized by complex impedance spectroscopy [2,6] using silver as an electrode material (σ=g/R, where g=l/s). In Fig.…”

“…To explain these results, it is important to take into account the occurrence of kinetic demixing phenomena during the sintering process [2,6]. The X-ray photoelectron spectroscopy (XPS) analyses results reported in Table 1 show the influence of the grain size, of the amount of Gd, and of the cooling rate at the end of sintering on the amount of Gd segregated at the periphery of the grains (depth close to 0.2 nm).…”

“…3, we have reported the microstructure of a reference ceria sample doped with Gd (10 mol% Gd 2 O 3 ) and obtained by natural sintering of nanocrystalline powders at 1,400°C during 2 h [2]. These sintering conditions lead to a final average grain size of about 500 nm (Fig.…”

Oxygen ion conducting glass ceramic composites for high temperature sensor applications

“…In such applications, ionic conductivity of the oxygen ion conductor plays an important role vide the Nernst equation. These oxygen ion sensors must have ionic conductivity in the range of 0.1-0.001 S cm -1 at given operating temperature range (500-700 ˚C) to create a measurable open circuit voltage (OCV) [6]. Gadolinium doped Ceria possesses ionic conductivity in above mentioned range.However, being a ceramic material, it requires higher sintering temperature in the range of 1200-1600 °C to achieve desired density (>96 % of theoretical density), which is an important factor affecting ionic conductivity [7].…”

Nanocrystalline Gadolinium doped Ceria (Ce<inf>0.8</inf>Gd<inf>0.2</inf>O<inf>3-&#x03B4;</inf>) for oxygen sensor and solid oxide fuel cell applications

“…According to Nernst equation, any increase in the ionic conductivity would increase the open circuit voltage of the conductor, in turn improving sensitivity of the sensor. Yttrium doped (8 mole%) Zirconia (YSZ) is a commonly used high temperature oxygen sensor [4]. This material shows high oxygen ionic conductivity of about 0.1 S/cm at 900 o C temperature [5,6].…”