Dense composite electrolytes of Gd3+ -doped cerium phosphates for low-temperature proton-conducting ceramic-electrolyte fuel cells

摘要

Dense Gd3+-doped cerium pyrophosphate phosphate (CGP-P) composites are prepared by infiltrating H3PO4 into partially sintered CGP substrates and then heat-treating at 375-400 degrees C. The phase composition and microstructure of CGP-P composites are studied by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM), which shows that the H3PO4 reacts with CGP to form phosphate phases in the pores and results in a dense CGP-P composite. The ionic conductivity of CGP-P composite is studied by electrochemical impedance spectroscopy (EIS) in dry and humid atmosphere in 90-230 degrees C range for its application as electrolyte in proton-conducting ceramic-electrolyte fuel cells (PCFCs). It is observed that the ionic conductivity of the composite GCP-P-1h/375, formed by 1 h acid-treatment followed by heat-treatment at 375 degrees C, is 2.73 x 10(-6) S cm(-1) at 230 degrees C in unhumidified air but in humidified air (water vapor pressure, pH(2)O = 0.12 atm) it shows a maximum of 0.051 S cm(-1) at 170 degrees C, which is significant for its application as electrolyte in PCFCs. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.