THIN-FILM COMPOSITE MIXTURES OF YBA2CU3O7-DELTA AND Y2O3

Thin-film, composite mixtures of YBa2Cu3O 7-δ (YBCO) and Y2O3 (yttria) have been grown by off-axis sputtering onto (100) SrTiO3 and (100) and (110) MgO. X-ray-diffraction measurements for films grown on (100) substrates show the presence of c-axis-oriented YBCO and (h00)-ordered yttria. The composites deposited on (110) MgO are insulating, and x-ray analysis shows the presence of Y2Ba1Cu1O5 along with c-axis YBCO. Scanning electron microscopy analysis shows the films to be very granular. The superconducting transition temperature and resistivity ratios between 300 and 100 K of the composites grown on the (100) substrates have been measured. A dramatic change is seen in these transport properties around 70% (volume) of YBa2Cu3O7-δ, which may be explained by the phase diagram for Y-Ba-Cu-O. © 1995 American Institute of Physics.