The physical and electromagnetic properties of Y‐Ba‐Cu‐O superconductors synthesized with BaO2(barium peroxide) have been studied. A comparison of reactions with BaCO3and BaO indicates that the peroxide promotes formation and strong alignment of platelet grains in planes normal to thecaxis, yields material with larger grain sizes and aspect ratios, reduces the synthesis reaction time by over half, increases the volume fraction of material that goes superconducting (Meissner effect), and facilitates metallic conduction in the normal state. Critical current densities of 1.1×104A/cm2at 77 K have been observed in peroxide‐synthesized material. These beneficial effects may be due to the low melting temperature of BaO2(450 °C), and the elimination of residual unreacted BaCO3, BaO, and/or C.