Structural and luminescent properties of europium doped TiO₂thick films synthesized by the ultrasonic spray pyrolysis technique

Abstract

The structural and luminescent properties of trivalent europium-doped titanium dioxide films synthesized by the ultrasonic spray pyrolysis technique at several substrate temperatures are reported. These films are nanocrystalline and present a mixture of tetragonal (anatase and rutile) crystal structures of the titania as determined by x-ray diffraction. The rutile crystal structure became predominant as the substrate temperature during deposition was increased. Under UV and electron beam excitation, these coatings showed strong luminescence due to f–f transitions and the dominant transition was the hypersensitive 5D0 → 7F2 red emission of Eu3+. The photo- and cathodoluminescence characteristics of these films were studied as a function of growth parameters such as substrate temperature and europium concentration. Excitation with a wavelength of 396 nm resulted in photoluminescent emission peaks located at 557, 580, 592, 615, 652 and 703 nm, associated with the electronic transitions of the Eu3+ ion. The photoluminescence (PL) intensity as a whole is observed to decrease as the deposition temperature is increased. Also, with increasing doping concentration, a quenching of the PL is observed. The chemical composition and surface morphology characteristics of the films are also reported.

Effects of crystallization and dopant concentration on the emission behavior of TiO2:Eu nanophosphors

“…When the sample is annealed at 500°C, all the PL emissions almost disappeared (Figure 10). This could be related to the transformation of amorphous titania to a fully crystalline anatase phase which presents a higher density, making more difficult for Eu +3 ions to locate at the site of Ti +4 due to the large difference in their ionic radii [42]. Thus, the well-dispersed Eu +3 ions in the unannealed amorphous titania tend to be segregated outwards.…”

Single Particle Cathodoluminescence Spectroscopy with Sub-20 nm, Electron-Stable Phosphors

“…The single-particle spectrum from BaYF 5 :Eu 3+ was the weakest of those acquired during the course of this study, yet the 5 D 0 → 7 F 4 centered at 705 nm and 5 D 0 → 7 F 1 centered at 600 nm are observable in the single-particle spectrum . Previous reports on Eu-doped ceramics have more frequently reported the 5 D 0 → 7 F 2 transition to be of highest intensity in the CL spectrum, suggesting BaYF 5 lattices may promote select quantum transitions not seen in other ceramic hosts such as Y 2 O 3 or TiO 2 . For BaYF 5 :Pr 3+ , the ensemble and single-particle spectra were identical, with maximum emission occurring at 615 nm corresponding to the 1 D 2 → 3 H 4 transition .…”

“…39 Previous reports on Eu-doped ceramics have more frequently reported the 5 D 0 → 7 F 2 transition to be of highest intensity in the CL spectrum, suggesting BaYF 5 lattices may promote select quantum transitions not seen in other ceramic hosts such as Y 2 O 3 or TiO 2 . 40 For BaYF 5 :Pr 3+ , the ensemble and single-particle spectra were identical, with maximum emission occurring at 615 nm corresponding to the 1 D 2 → 3 H 4 transition. 41 Generally, single-particle and ensemble CL spectra of lanthanide-doped nanophosphors match well with regard to the emission maxima of distinct lines and their relative intensities.…”

Effect of metal ions doping on structural, optical properties and photocatalytic activity of anatase TiO2 thin films

“…26,27 Many techniques are available for the coating of TiO 2 thin films on various substrates such as pulsed laser deposition (PLD), 28 RF. Magnetron Sputtering, 29 electron-beam evaporation, 30 hydrothermal method, 31 spray pyrolysis, 32 chemical vapour deposition 33 and sol-gel spin coating. 5,34 In this paper, the sol-gel spin coating has been used to synthesize TiO 2 thin films due to its vital role in sample properties, that is, cost-effectiveness, simple technique and ability to produce high-quality films, improved transparency and better homogeneity.…”