| Autor: |
Bessergenev VG; Centre of Marine Sciences (CCMAR), Campus de Gambelas, Universidade do Algarve, FCT, 8005-139 Faro, Portugal., Mariano JF; CeFEMA, Campus de Gambelas, Universidade do Algarve, FCT, 8005-139 Faro, Portugal., Mateus MC; Centro de Investigação em Química do Algarve (CIQA), Campus de Gambelas, Universidade do Algarve, FCT, 8005-139 Faro, Portugal., Lourenço JP; Centro de Investigação em Química do Algarve (CIQA), Campus de Gambelas, Universidade do Algarve, FCT, 8005-139 Faro, Portugal.; Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1096-001 Lisbon, Portugal., Ahmed A; Institute of Physics, University of Rostock, 18055 Rostock, Germany., Hantusch M; IFW Dresden, Helmholtzstraße 20, 01069 Dresden, Germany., Burkel E; Institute of Physics, University of Rostock, 18055 Rostock, Germany., Botelho do Rego AM; CQFM, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisbon, Portugal. |
| Abstrakt: |
Dielectric properties and spectral dependence of the photocatalytic constant of Co doped P25 Degussa powder were studied. Doping of TiO 2 matrix with cobalt was achieved by precipitation method using of Tris(diethylditiocarbamate)Co(III) precursor (CoDtc-Co[(C 2 H 5 ) 2 NCS 2 ] 3 ). Five different Co contents with nominal Co/Ti atomic ratios of 0.005, 0.01, 0.02, 0.05 and 0.10 were chosen. Along with TiO 2 :Co samples, a few samples of nanopowders prepared by Sol-Gel method were also studied. As it follows from XPS and NMR studies, there is a concentration limit (TiO 2 :0.1Co) where cobalt atoms can be uniformly distributed across the TiO 2 matrix before metallic clusters start to form. It was also shown that CoTiO 3 phases are formed during annealing at high temperatures. From the temperature dependence of the dielectric constant it can be concluded that the relaxation processes still take place even at temperatures below 400 °C and that oxygen defect Ti-O octahedron reorientation take place at higher temperatures. The spectral dependency of the photocatalytic constant reveals the presence of some electronic states inside the energy gap of TiO 2 for all nanopowdered samples. |
