Characterization of EuBa2Cu3Oy Synthesized in Shock Processes

We synthesized a homogeneous, tetragonal EuBa2Cu3Oy with c/a=3.00 by the shock compression method. The phase is considered to be similar to the tetragonal YBa2Cu3Oy metastably formed at relatively low temperature with the c/a ratio=3.00. Electron diffraction patterns indicate ordering of Eu and Ba atoms to some extent, but ordering is presumably not perfect. High resolution trasmission electron microscory images show that shock-synthesized EuBa2Cu3Oy consists of 60-80-A-size domains, whose principal axes are perpendicular to each other. Perfect ordering of Eu and Ba atoms was achieved by annealing the shock-synthesized specimen above 900° C, resulting in the increase of the c/a ratio from 3.00 to 3.05 as well as superconduction upon O2 annealing. This result is explained by the shortness of the reaction time in shock processes.