Structural, morphological and electrical properties of alumina/YAG composites as solid electrolyte for IT - SOFC

Abstract

Alumina/YAG composites (AYX_t) with high relative density (99.2 %TD) were successfully obtained by mixing commercial alumina powder with different volume fractions of yttrium aluminium garnet (Y 3 Al 5 O 12-YAG; 7, 14, 21 and 28). YAG was synthetized by nitrate glycine reaction in the form of precursor powder. Polycrystalline YAG powder was obtained by calcination at 950 °C for 2 h. Additionally, obtained compositions were characterized by XRD, SEM, EDX and electrochemical impedance spectroscopy. By XRPD analysis was found that the particle size of YAG powders lies in the nanometric range (being lower than 35 nm). By SEM microphotographs of composites were confirmed the formation of a conductive path consisting from mutually interconnected YAG particles. This was confirmed by the electrochemical impedance spectroscopy. The highest electrical conductivity of grain (κ g) and grain boundary (κ gb) at 700 ºC amounted to 2.22×10-2 Ω-1 cm-1 and 9.44×10-3 Ω-1 cm-1 , respectively, was measured in the composite containing 21 vol% of YAG.

Geopolymer/CeO2 as Solid Electrolyte for IT-SOFC

“…In this context, with the advances in ceramic processing technology, ceramic-matrix composites have been increasingly used in recent years [16,17]. Good examples for that are multidoped calcium phosphate and alumina/YAG [16,17], or aluminosilicates [18]. The aluminosilicate ceramica in form of a geopolymer (GP) represent one of the few alternatives as a potential low-cost material for solid oxide fuel cell applications [18].…”

“…The appearance of microgalvanic couples and ion-electron processes through formed solid phases present additional micromorphology secondary changes [24]. In contrast to perovskite and fluorite, in which oxide ion conduction proceeds via oxygen vacancies [6,[14][15][16][17][18][19][20], the research of geopolymer materials suggests that conductivity involves interstitial or free ions [6]. Recent papers show a wide range of cation substitutions due to the flexibility of the structure in accommodating a range of ion sizes [25][26][27].…”