The Effect of Ionic Radius Difference of RE3+and Ba2+on the Shock Synthesis of REBa2Cu3Oy(RE=Y, Eu, La)

Abstract Shock-synthesis experiments of REBa 2 Cu 3 O y (RE=Y, Eu, and La) were carried out for the mixture of component oxides as starting materials using a 25 mm-bore propellant gun. Both tetragonal EuBa 2 Cu 3 O y with c / a =3.00 and cubic LaBa 2 Cu 3 O y were successfully synthesized by shock compression, but YBa 2 Cu 3 O y was synthesized only partly. The optimum condition for obtaining maximum yield of shock-synthesized EuBa 2 Cu 3 O y and LaBa 2 Cu 3 O y was shock compression of the starting materials with 40% porosity to 30 GPa. La 1+ x Ba 2− x Cu 3 O y could also be synthesized, but Eu 1+ x Ba 2− x Cu 3 O y could not. Shock-synthesized EuBa 2 Cu 3 O y and LaBa 2 Cu 3 O y were in a metastable phase in which RE 3+ and Ba 2+ were not ordered perfectly; they converted to the phase synthesized by conventional solid state reaction when annealed above 900°C. Only after annealing above 900°C, followed by oxidation at 400°C, did EuBa 2 Cu 3 O y exhibit superconductivity with T c ≒71 K. These results suggest that shock synthesis of REBa 2 Cu 3 O y becomes easier with a decrease in the difference between ionic radii of RE 3+ and Ba 2+ .