Electrochemical fabrication of luminescent CaWO4 and CaWO4 : Pb films on Wsubstrates with anodic potential pulses

Luminescent polycrystalline films of CaWO4 and CaWO4:Pb2+ have been prepare d on tungsten substrates by applying low anodic potential pulses at tungste n electrodes in alkaline solutions containing calcium ion or calcium and le ad ions. Anodically grown CaWO4 films show weak luminescence and broad X-ra y diffraction peaks. The luminescence band of the film is shifted toward a longer wavelength (red shift) compared with that of the CaWO4 powder prepar ed by a conventional solid-state method. By postannealing the anodically go wn CaWO4 film at high temperatures, luminescence intensities are enhanced, and the luminescence band maximum has been blue shifted to 420 nm. CaWO4 fi lms doped with a trace amount of Pb2+ ion, electrochemically prepared in al kaline solutions containing calcium and lead ions, show a decrease in the i ntensity of luminescence maybe because of hydroxides or of hydrated water. By postannealing, the intensity of luminescence is enhanced dramatically, a nd the luminescence band maximum is red shifted to 444 nm in comparison to that of undoped CaWO4 films. (C) 1999 The Electrochemical Society. S0013-36 51(98)12-005-0. All rights reserved.