Electrical & magnetic properties of YBa₂Cu_3+xO_7+d (x=0, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 1) superconducting materials, prepared by standard solid state reaction technique, is reported. X-ray diffraction pattern of the samples show that the structure of the samples were orthorhombic and single phase. The superconducting transition temperature T_c was determined from DC resistance and AC susceptibility measurement. DC resistance measurement for YBa₂Cu_3+xO_7+d sample with x=0 showed a sharp superconducting transition having an onset temperature of about 91K. The AC resistance measurement also showed that the transition temperature T_c decreases as the copper concentration in the sample increases.The oxidation states of the samples increase with increasing copper content. It was observed that T_c decreases as copper content increases in the samples. The YBa₂Cu₄O_7+d sample is a suppression of 2^nd order phase transition (orthorhombic to tetragonal), which is a well known characteristic feature of YBa₂Cu₃O_7+d superconductor. The stable oxygen content in YBa₂Cu₄O_7+d makes the structure thermodynamically stable than the YBa₂Cu₃O_7+d and as a result, no oxygen vacancies or twin structures are present in the YBa₂Cu₄O_7+d sample.