Electrical conductivity of Y2O3-doped CeO2 based composite ceramics by spark plasma sintering: The effects of a second phase of CeAlO3

The Ce 0.85 Y 0.15 O 2-δ (YDC)-xmol% aluminum containing compound (x = 0, 10, 20 and 40) composite powders were prepared through mixing YDC with 0, 10, 20 and 40 mol% Al(NO 3 ) 3 (named as A0, A10, A20, A40), and then densified by spark plasma sintering at 1300 °C for 5 min. The main phase of YDC exists in all samples, while a second phase of CeAlO 3 forms for x ≥ 10 in the composite ceramics. The diffraction peak intensity of CeAlO 3 gradually augments with the increase of Al(NO 3 ) 3 addition amount. The average grain size of the composite ceramics reduces from 1.7 μm to 0.34 μm with the rise in Al(NO 3 ) 3 addition amount from 0 to 40%. The grain boundary (GB) electrical conductivity of A10 and A20 is lowered by 96% and 89% compared with that of YDC at 350 °C because the CeAlO 3 phase exists in the form of flakes and fine grains and hinders the oxygen ion conduction across the GB of samples. When CeAlO 3 grains grow up and uniformly distribute in the A40, the GB conductivity of A40 increases by 405% relative to that of pure YDC at 350 °C.