In this work, Y3(Ba1−xCax)5Cu8O18 compounds with x = 0.00, 0.01, 0.02, 0.03 and 0.05 were synthesized by thermal treatment of aqueous solution of metal nitrates and polyvinylpyrrolidone (PVP). The effects of Ca substitution on the crystal structure, electrical resistance and the microstructure of samples were investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), four-point probe measurement and AC susceptibility. FESEM analysis showed that there was an increase in the grain size and compactness. The zero-resistance critical temperature decreased from 92 K for the pure sample to 83 K for sample x = 0.05. From AC susceptibility result, the intra- and inter-granular loss peaks shifted toward lower temperature and become wider and broader with the increase of Ca substitution due to the weakening of grain coupling. On the other hand, the inter-granular critical current density (Jcm) was found to increase with Ca substitution and has the highest value Jcm = 35 A cm− 2 at x = 0.05, indicating that the Ca substitution was associated with the formation of pinning centres in the Y-358 matrix. [ABSTRACT FROM AUTHOR]