Preparation of High T sub c and J sub c films of Ba sub 2 YCu sub 3 O sub (7-delta) by laser evaporation and observation of superconductivity in a 27angstrom phase.

High T sub c and J sub c superconducting films of Ba sub 2 YCu sub 3 O sub 7 are prepared on (100) SrTiO sub 3 substrates using pulsed excimer laser vaporization of a composite target containing BaF sub 2, Y sub 2 O sub 3, and CuO, followed by annealings in wet oxygen. High transition temperatures (R=O from 89.5-91K) and high critical current densities (J sub c >= 7x10 sup 5 A-cm sup (-2)) are achieved. The electrical transport properties of these films are significantly better than films previously grown using Ba-Y-Cu-O targets. In addition, high purity (>97%) samples of a 27angstrom phase of Y-Ba-Cu- O have been prepared on (100)SrTiO sub 3.