Effect Of The Gadolinium Oxide Addition On The Electrical Properties Of Tetragonal Zirconium Dioxide

Abstract

The aim of this work was examination of gadolinium-doped 3YSZ electrical and structural properties. Such materials may be used as electrolytes in intermediate temperature solid oxide fuel cells (IT-SOFC). First step of the research was synthesis of 3YSZ with different contents of gadolinium ( 0.25; 0.5; 1.0 at %). Prepared materials were characterized by high porosity. No effect of gadolinium addition on grain size was observed. The experimentally determined values of grain interiors electrical conductivities for gadolinium doped samples are comparable to grain interior conductivities of gadolinium free tetragonal zirconia. On the other hand, a clear effect of gadolinium addition on electrical conductivity of grain boundaries was observed. It was found that 3YSZ containing 0.25 at. % Gd was the most promising from the investigated materials as a solid electrolyte for IT SOFC.Keywords: Gadolinium (III) oxide, tetragonal zirconia, electrical properties, grain boundary conductivity Celem pracy było zbadanie strukturalnych i elektrycznych właściwości dwutlenku cyrkonu stabilizowanego 3% mol. tlenkiem itru (3YSZ) z dodatkiem gadolinu. Tego typu materiał może znaleźć zastosowanie jako elektrolit w średniotempe-raturowych stało-tlenkowych ogniwach paliwowych (IT-SOFC). Pierwszym etapem badań była synteza 3YSZ z różną ilością wprowadzonego gadolinu (0.25; 0.5; 1.0 at %). Otrzymane materiały charakteryzowały się wysoką porowatością. Nie zaobserwowano wpływu dodatku gadolinu na wielkość ziaren. Wyznaczone eksperymentalnie wartości przewodnictwa objętości ziaren są porównywalne z wartością przewodnictwa objętości ziaren wykazywanego przez czysty 3YSZ (bez dodatku gadolinu). Z drugiej strony, zaobserwowano znaczny wpływ dodatku gadolinu na przewodnictwo po granicach ziaren. Stwierdzono również, że 3YSZ zawierający 0.25% at. gadolinu był najbardziej obiecującym z badanych materiałów pod kątem zastosowania jako elektrolit w IT -SOFC.

Densification and microstructure of spark plasma sintered 7YSZ–Gd2O3ceramic nano-composites

“…In our case, an overshoot effect could cause an increment of temperature at surface contact between 7YSZ powder and Gadolinia particle, and then the formation of a solution solid in the 7YSZ grain boundary with Gd 2 O 3 . Recent studies show the conductivite effect of Gadolinium Oxide in tetragonal dioxide zirconium [57]. These experimentally results of grain interiors electrical conductivities for gadolinium-doped samples are comparable to grain interior conductivities of gadolinium free tetragonal zirconia.…”

“…This overshooting effect is a very important behavior during SPS process. For non-conductive (YSZ) monophase sample, the core of the sample is at a lower temperature than that measured on the surface of the die, while, for the conductive solid mixture (in our case 7YSZ with Gadolinia) (electric conductivity; Gd 2 O 3 −6.5 to −3.5, and 10YSZ 10 −4 to 10 −2 S cm −1 ) [57][58][59], which can be self-heated to some extent by Joule heating, the temperature of the core of the sample can be higher than that measured on the surface of the die. The temperature difference between the measured temperature (on the surface of the die) and the actual temperature (on the surface of the sample) has been reported varies about 140 • C and 170 • C for nonconducting silicon nitride and conducting tungsten carbide respectively [36].…”

Structural and morphological analysis of barium cerate electrolyte for SOFC application

“…In order to overcome these problems, the operating temperatures of the fuel cell must be reduced to intermediate temperatures (between 500°C to 700°C) by choosing a suitable alternative electrolyte with high ionic conduction. Lowering the operating temperatures of electrolyte will ultimately extend the lifetime of fuel cells and the replacement of expensive ceramic interconnects by stainless steel may be possible for lower temperatures operation [2]. The oxygen-ion conducting electrolytes are a good choice to achieve high ionic conductivity in solid ceramics operated at lower temperatures.…”