Electrical characterization of La9.33Si2Ge4O26 oxyapatite for prospective intermediate-temperature solid oxide fuel cells

Abstract

La9.33Si2Ge4O26 materials have been fabricated from La2O3, SiO2 and GeO2 powders by high speed mechanical alloying followed by conventional and microwave hybrid sintering at different temperatures and holding times. XRD data showed that the apatite phase is formed after 1h of mechanical alloying at 850rpm. This phase remained stable after conventional sintering in an electric furnace with density increasing as sintering temperatures and holding times were increased. However, the highest density was achieved for samples sintered in the microwave furnace (5.44gcm−3), corresponding to a relative density of 98%. The electrical conductivity of the samples microwave sintered at 700 and 800ºC are 4.72×10−3 and 1.93×10−2 S.cm−1, respectively, with a correspondent activation energy of 0.952eV.