Effect of pH value on the synthesis and characterization of Ba _(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O _(3-δ) powders prepared by the citrate-EDTA complexing method

摘要

This study reports the successful preparation of potential candidate Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O _(3-δ) (BSCF) oxides for intermediate-temperature solid oxide fuel cells (IT-SOFCs) by a combined citrate-ethylenediaminetetraacetic acid (EDTA) complexing method. The resulting crystal properties, chemical composition, conductivity, and electrochemical properties were studied by X-ray diffraction (XRD), inductively coupled plasma mass spectroscopy (ICP-MS), energy dispersive spectrum (EDS), four-point DC measurement and AC impedance. The X-ray diffraction results of all samples with different pH values reveal a basic perovskite structure. Although samples prepared from different pH solutions have a similar structure, their chemical composition and grain morphologies are different. The optimized composition of BSCF is the sample prepared from the precursor solution with a pH value of 6; this produced highest conductivity at 50.2 S/cm at 400 °C, which is 1.3 times higher than the sample prepared from the precursor solution with a pH value of 9. Electrochemical impedance spectra at an intermediate temperature reveal the better electrochemical performance of BSCF electrode prepared from the solution with pH of 6. The lowest polarization resistance values for charge transfer and oxygen diffusion are 0.07 and 0.11 Ω cm~2 at 800 °C, respectively.