Microstructure and electrical properties of 3Y‐TZP/Al₂O₃ composite obtained using the citrate gel method

Abstract

3Y-TZP sinters with 1, 5, 10, and 15 mol% of Al 2 O 3 were prepared using two different procedures from a 3-YSZ powder synthesized via the citrate process. In the first procedure, alumina was introduced during synthesis via the citrate method. In the second one, the 3-YSZ powder was impregnated with aluminum nitrate. All samples were sintered at 1773 K. The prepared composites were evaluated in terms of their microstructure, chemical and phase composition, and electrical properties. The total conductivity of the 3Y-TZP/Al 2 O 3 composite material, which contained primarily the tetragonal phase, was found to increase with temperature, and to decrease for reduced concentrations of alumina in 3Y-TZP. In the case of the samples which had alumina introduced via impregnation, its higher content was not associated with significantly lower electrical conductivity. These samples generally exhibited higher conductivity than the samples to which alumina had been added via chemical synthesis.

Effects of Aluminum Oxide Addition on Electrical and Mechanical Properties of 3 mol% Yttria-Stabilized Tetragonal Zirconia Electrolyte for IT-SOFCs

“…Alumina acts as an insulator, which is why higher concentrations of this compound affect activation energy in this way. The activation energy of the grain boundary conductivity was higher than the activation energy of the grain interior conductivity, which is consistent with the results presented in [ 31 , 63 , 67 ]. In the case of GS sinters, the activation energy values of grain interior and grain boundary conductivity were comparable regardless of the concentration of Al 2 O 3 inclusions.…”

“…The activation energy of total conductivity (E a(tot) ) was in the range of 0.79–0.82 eV for the GS sinters and in the range of 0.76–0.82 eV for the IS ones. Similar values have been reported in the literature for this type of ceramics [ 30 , 31 , 40 , 62 , 63 ]. GS-15 had the highest E a(tot) value of the samples from the first group, while in the second group the highest value was found for IS-10.…”

“…As per the generally accepted interpretation, the phenomena taking place in the grain interiors, grain boundaries and electrodes are observed for different frequency ranges. The impedance spectrum for the range of high frequencies (first semicircle) is associated with the electrical conductivity of the grain interior, whereas for lower frequencies (second semicircle) a response originating from the electrical conductivity of grain boundaries is observed [ 49 , 63 ].…”