In this study, phase synthesis and electrochemical properties of Sm1-xNdxBa0.5Sr0.5CO2O5+d (x = 0-0.9) oxide systems where neodymium and samarium were replaced at the A-site of SmBa0.5Sr0.5CO2O5+d layered perovskite are investigated for use as cathode materials in Intermediate Temperature-operating Solid Oxide Fuel Cells (IT-SOFCs). The structure of Sm1-xNdxBa0.5Sr0.5CO2O5+d (x = 0-0.9) oxide systems can exist in either an orthorhombic (x = 0-0.4) or tetragonal (x = 0.5-0.9) form. The maximum electrical conductivities in Sm1-xNdxBa0.5Sr0.5CO2O5+d (x = 0-0.9) oxide systems were obtained from Sm0.2Nd0.8Ba0.5Sr0.5CO2O5+d (SNBSC08) and their values are 1280 and 280 Scm(-1) at 50 degrees C and 900 degrees C, respectively. The area specific resistances (ASRs) of SBSCO are 3.019, 0.611, and 0.092 Omega cm(2) at 500, 600, and 700 degrees C, respectively. However, SNBSCO8 single phase gives the lowest ASRs of 1.751, 0.244 and 0.044 Omega cm(2) at the same temperatures tested. SNBSCO8 is thus a promising candidate cathode material for IT-SOFC applications. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.