Preparation to High T sub c and J sub c Films of Ba sub 2 YCU sub 3 O sub 7 By Laser Evaporation and Observation of Superconductivity in a 27A Ba-Y-Cu-O Phase

High T sub c and J sub c superconducting films of Ba sub 2 YCu sub 3 O sub 7 are readily prepared using laser vaporization of bulk materials. The output from a pulsed excimer laser is used to vaporize material from a composite target containing BaF sub 2, Y sub c O sub 3, and CuO onto (100) SrTiO sub 3 substrates. The superconducting phase is subsequently formed during post deposition annealings in wet oxygen. High transition temperatures (R=0 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.