Optimisation of the properties of high-T/sub c/ thick films

High-T/sub c/ thick films of YBa/sub 2/Cu/sub 3/O/sub 7-/spl part// (YBCO) are potentially useful in various applications; for example in practical fault current limiters in the field of power engineering. The material also shows promise in the fabrication of numerous microwave devices. However it is of paramount importance to optimise their microstructure and properties, with particular respect to the critical current density (J/sub c/) and surface resistance (R/sub s/). Doping and barrier layer technology have been used to improve the characteristics of the films. Enhanced current carrying capacity is achieved as a result of doping with Pt and a Ba/sub 4/Cu/sub 1+x/Pt/sub 2-x/O/sub 9-z/ (0412) compound Exploitation of low dielectric loss and economically attractive alumina substrates has also been achieved, by means of barrier layers. The relation between the processing, microstructure and superconducting behaviour is reported.