Optical properties of rare-earth ion (Gd3+, Ho3+, Pr3+, Sm3+, Dy3+ and Tm3+) -doped alumina films prepared by the sol–gel method

Rare-earth ions (Gd3+, Ho3+, Pr3+, Sm3+, Dy3+ and Tm3+)-doped alumina films were prepared by the sol–gel method, using aqueous AlCl3-derived alumina sol. The ions were highly doped into alumina by this method (∼15 mol% per alumina). Then, the absorption and fluorescence spectra of the doped films were measured. The first three ion-doped films showed quenching at higher concentrations (>15 mol%) and the last three ion-doped films quenching at lower concentrations (≥0.5 mol%). The quenching composed of a fast component and the slow one which depended on different sites of disordered alumina.