The effect of volatile boron species on the electrocatalytic activity, microstructure and phase stability of conventional La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) and nano-structured LSCF infiltrated Gd0.1Ce0.9O1.95 (LSCF-GDC) electrodes of solid oxide fuel cell (SOFC) is studied. The cathodes were heat-treated at 700-800 degrees C for 7-30 days in air in the presence of borosilicate glass. Heat-treatment in the presence of glass has a significantly detrimental effect on the microstructure and electrochemical activity of the cathodes. For example, the electrode polarization resistance (R-E) of a freshly prepared LSCF cathode is 0.07 Omega cm(2) at 800 degrees C, and increases significantly to 84 Omega cm(2) after heat-treated at 800 degrees C for 30 days in the presence of glass. Similar degradation behavior was also observed on infiltrated LSCF-GDC electrodes. Present study shows that boron is not chemically compatible with LSCF and the interaction results in the disintegration and decomposition of LSCF perovskite structure, forming LaBO3 and Fe2O3. A reaction mechanism between volatile boron species and LSCF electrodes is proposed. (C) 2013 The Electrochemical Society. [DOT: 10.1149/2.019304jes] All rights reserved.