CADMIUM-INDUCED GROWTH OF 2223-PHASE AND T-C ENHANCEMENT IN TBCCO HIGH T-C THIN-FILMS

Cd doped Tl-2223 thin films (similar to 1 mu m) have been grown by ann ealing B2Ca2CdxCu3Oy (x = 0.0, 0.1, 0.2, 0.3) precursor films, deposit ed on MgO (100) by ultrasonic spray pyrolysis, in Tl2O ambient in an e vacuated (> 10(-5) Torr) sealed quartz tube at 890 degrees C for 2 h. Doping by Cd has been found to induce the growth of 2223 phase and an enhancement in T-c. The Te of the as-grown thin films samples are 118 K, 120 K, 124 K and 121 K respectively for Cd contents x = 0.0, 0.1, 0 .2 and 0.3. The observed T-c= 124 K for x = 0.2 is higher than the pre viously observed highest T-c of 122 K for Tl-2223 thin films. A distin guishing feature of the present synthesis route is the fact that oxyge n has not been used at all in the entire synthesis process. The transp ort J(c) of the 0.2 Cd doped film is 1.12 x 10(5) A/cm(2) (77 K, 0 T). The surface morphology of these films shows a very dense growth of pl atelet-like grains. (C) 1998 Published by Elsevier Science B.V.