THE MICROSTRUCTURE AND ELECTRICAL-PROPERTIES OF TL2BA2CA1CU2OX THIN-FILMS PROCESSED AT LOW-TEMPERATURES

Tl2Ba2Ca1Cu2Ox thin films on (001) LaAlO3 with excellent alignment sui table for microwave applications at 77 K have been fabricated using an ex situ anneal step in argon atmospheres at temperatures of 720-740 d egrees C. Surface resistance values as low as 400 mu Omega (79 K, 10 G Hz) and large-area critical current densities up to 3.4 x 10(5) A cm(- 2) (77 K) have been achieved. In order to understand the relationship between the microstructure and electrical properties the films have be en characterized by a variety of techniques, but especially transmissi on electron microscopy and allied methods. Microstructural features su ch as a-axis oriented grains, secondary phase particles, grain boundar ies and surface outgrowths (especially of non-superconductor phases) h ave been found to have a significant effect on the surface resistance.