Red Photoluminescence of Pr³⁺-doped TiO₂-NbO_2.5 thin films

Abstract

Photoluminescence (PL) spectra of Pr³⁺-doped TiO₂-NbO_2.5 thin films synthesized by a sol-gel method were reported. NbO_2.5 content (x) was varied from 2.4 to 10 mol%. For x=2.4, no PL was observed. It was thought that Pr³⁺ was not substituted with Ti in TiO₂ lattice structure because of the large ionic radius of Pr³⁺ in comparison with Ti⁴⁺. On the contrary, red PL of ¹D₂-³H₄ of Pr³⁺ was increased with increasing NbO_2.5 content. It is presumably because NbO_2.5 rich region in TiO₂-NbO_2.5 allowed Pr³⁺ ions to be doped in the lattice structure and to be excited via band-to-band excitation of TiO₂:Nb.