Investigations on the magnetic properties of thick films of BKBO

Single crystalline thick films of the superconductor Ba1-xKxBiOy with wide range of composition I were studied. We first prepared the superconducting films with potassium content x = 0.55 to 0.67. The systematic exploration o f the thick films with T-c approximate to 30-31 K and J(c)(5 K) approximate to 5 x 10(5) Acm(-2) (x = 0.36 and 0.38) reveals that for 4.2 to 20 K the field dependences J(c)(B) are well described by the collective pinning theo ry. The investigation of the pinning force density F-p(B) shows an unusual scaling behaviour for thick film with x = 0.38.