Impedance analysis of Sr-substituted CePO4 with mixed protonic and p-type electronic conduction


Members of the solid-solution series Ce1-xSrxPO4-delta (x = 0, 0.01, 0.02) with mixed protonic and electronic transport have been synthesized by a nitrate-decomposition method followed by sintering at 1450 degrees C. Impedance spectroscopy is employed to estimate the bulk electrical conductivity in wet (similar to 0.03 atm) and dry atmospheres of O-2 and 10%H-2:90%N-2. Conductivity increases with dopant concentration (x), oxygen partial pressure (pO(2)) and water vapour partial pressure (pH(2)O) reaching similar to 3.5 x 10(-3) S cm(-1) at 600 degrees C for x = 0.02 in wet O-2. Activation energies (E-a) for the bulk conductivity of Ce0.98Sr0.02PO4-delta below 650 degrees C are 0.44 and 0.78 eV for wet oxidising and wet reducing conditions, respectively. A moderate but positive pO(2)(+n) power-law dependence (n < 1/10) of conductivity is exhibited in the pO(2) range 10(-2.5) to 10(-1) atm, consistent with mixed ionic and p-type electronic transport. Thermogravimetric analysis indicates that the Sr-doped materials are stable in a CO2 atmosphere in the temperature range 25-1200 degrees C. (C) 2008 Elsevier Ltd and Techna Group S.r.l. All fights reserved.



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Materials Science


del Moral, EG; Fagg, DP; Chinarro, E; Abrantes, JCC; Jurado, JR; Mather, GC

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