Platinum films, used in thin film technology, produced by radio-frequency sputter deposition on aluminium oxide substrates under different conditions, have been studied by positron beam and other techniques, before and after production annealing. The defect structure in the layers has been characterised using both positron Lifetime and Doppler-broadening spectroscopy, and compared with X-ray studies of crystallinity and texture. (C) 1999 Elsevier Science B.V. All rights reserved.