Improvement in the properties of high T c films fabricated in situ by laser ablation of YBa2Cu3O7-Ag targets

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Abstract
We have studied the microstructural and superconducting properties of YBa2Cu3O7 films fabricated by pulsed laser evaporation of YBa2Cu3O7‐Ag targets, containing approximately 30% by weight of silver. The films produced by excimer laser evaporation/ablation of YBa2Cu3O7‐Ag targets were found to possess better superconducting and microstructural properties than films prepared under the same conditions from bulk YBa2Cu3O7 targets. YBa2Cu3O7 films deposited on yttria stabilized zirconia (YSZ) substrates from YBa2Cu3O7‐Ag targets at 650 °C showed helium ion channeling yields of approximately 9%–12%, while films deposited from YBa2Cu3O7 targets had channeling yields in the range of 18%–25%. The critical current density of YBa2Cu3O7Agx films on YSZ substrates had values of approximately 1.8×106 A/cm2 at 77 K which corresponds to approximately an 80% improvement from the values obtained from films deposited from cold pressed YBa2Cu3O7 targets. Based on the structural and chemical information, it appears that two effects play a major role in improving the superconducting properties of laser ablated thin films made from silver composite superconductor targets (i) improved evaporation characteristics of the targets due to silver incorporation and (ii) the catalyst effect of silver in stabilizing the superconducting phase and enhancing grain growth.