Mechanical properties of lanthanum silicate oxyapatite (LSO) ceramics

RENDTORFF, NICOLÁS M.; MOREIRA TOJA, RAMIRO J.; SAKKA, YOSHIO; UCHIKOSHI, TETSUO; AGLIETTI, ESTEBAN F.; SUÁREZ, GUSTAVO

Congreso; 7th International Congress on Ceramics; 2018

Lanthanum silicate oxyapatites (LSO) are ceramic materials that show a good electric conduction at intermediate temperatures (600 ~ 800 oC). Interest in this kind of materials is related to the need for lower operation temperatures of solid oxide fuel cells (SOFCs), which would reduce operational and maintenance costs. It is desirable that solid electrolytes possess adequate mechanical properties to avoid cracking during operation and to assure a desirable performance [1, 2]. Apatyte-structured lanthanide silicates have been poorly described in relationship to their mechanical properties. In this work, we study LSO?s mechanical behavior in order to address this vacancy.LSO was synthesized per a solid state reaction method [3]. Rectangular cross-section bars were formed via uniaxially pressing grinded powder at 50 MPa and further isostatically pressing at 100 MPa for 5 minutes.Casted bars were dried at 110 oC for 24 hs and fired with a heating rate of 5 oC/min and 2 hours dwells at temperatures of 1100, 1200, 1300, 1400 and 1500 oC. Fired bars porosity and density were studied viaArchimedes method. Stress-strain curves from three point flexion arrangements were studied to obtain Young?s modulus and its flexural strength. Besides, Young?s modulus was compared with measurementsdone via impulse excitement method. Microhardness was studied with a Vickers indenter, and nanohardness of the pieces sintered at 1500 oC was studied with a Berkovich indenter.The mechanical properties of LSO are at a disadvantage if we compare these results with the traditionally used cubic yttria-stabilized zirconia, but the mechanical behavior shown in this work that this new materialcould be useful for solid oxide fuel cells.[1]Liu, Y. H. et al. Science of Sintering 40, 13?20 (2008).[2]Santos, M. et al. Ceramics International 38, 6151?6156 (2012).[3]Kobayashi, K. et al. Journal of the Ceramic Society of Japan 123, 274?279 (2015).