ELECTROLUMINESCENCE OF HO3-OXIDE ELECTRODES IN CONTACT WITH AQUEOUS-ELECTROLYTE( IONS IN SEMICONDUCTING POLYCRYSTALLINE ZINC)

Sintered semiconducting zinc oxide has been doped with varying amounts of Ho3+ ions and its electroluminescence has been studied under vario us polarization conditions. Under cathodic polarization and in the pre sence of persulfate ions, the emission of the ZnO matrix only was obse rved. Conversely, under anodic under anodic polarization, characterist ic emission bands of the Ho3+ ions were generated. The intensity of th ese bands was studied as a function of both the polarization potential and the rare earth doping. level. In the 9.8-10.2 V vs. SCE range, th e log of the emission intensity varied inversely with the square root of the applied potential, according to the Alfrey-Taylor relationship. It showed a maximum for a Ho3+ doping level of ca. 0.5 atom%. Analysi s of the samples' polycrystalline structure using scanning electron mi croscopy (SEM) and energy dispersive spectroscopy (EDS) techniques ind icates that the rare-earth ions create islands on the surface of ZnO w hich induce dislocations in the polycrystalline structure.