HREM INVESTIGATION OF GDBA2CU3O7-X FILMS GROWN ON MGO SUBSTRATES BY MAGNETRON SPUTTERING DEPOSITION

HREM studies of c-axis oriented GBCO films, with T-c > 90 K and J(c) > 10(6) A/cm(2) at 77 K, have shown that they contained two dense distr ibutions of particles, one coarse and one fine. The coarse particles w ere found to be composed of agglomerates of very fine a-axis oriented grains, having c-axes in two perpendicular directions, together with o ther second phases. The fine particles were isolated a-axis oriented g rains, some of which formed a 'sandwich' with Gd2O3 at the centre. Ant i-phase boundaries were frequently observed in the film and, grain bou ndaries with an angle of 45 degrees were occasionally observed.