A stable resistive transition in YBaCuO above 200 K

Precipitating a thin layer of the non-superconducting phase 211 in the superconducting matrix 123, we prepared a series of new ceramic samples of the system YBaCuO. The measurements of the a.c. electrical resistance and a.c. susceptibility show that, depending on the modifications in the technological process, these samples undergo a large or a narrow resistive transition to the superconducting state, at least in a.c., within the temperature range 180–250 K.