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Nebatti A.,University of Duisburg - Essen | Pflitsch C.,University of Duisburg - Essen | Eckert C.,University of Duisburg - Essen | Atakan B.,University of Duisburg - Essen | Atakan B.,Center for Nanointegration Duisburg
Progress in Organic Coatings | Year: 2010

A relatively new promising method for surface temperature measurement is the use of thermographic phosphors. For this application, the temperature-dependent luminescence properties of europium(III)-doped anatase (TiO2:Eu3+) thin films were studied. The films were prepared by the sol-gel method using dip coating. The structures and the morphology of the films were determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Electron dispersive X-ray spectroscopy (EDX) was used to verify the europium concentration within the films. For using the films as temperature sensors the optical properties are the main concern. Therefore, the emission spectra of the films were measured after ultraviolet laser excitation (355 nm). They indicate that the red characteristic emission (617 nm) of TiO2:Eu3+ due to the 5D0 →7F2 electric dipole transition is the strongest. The decay time constant of the exponential emission decay under UV excitation with a Nd:YAG laser (355 nm, f = 10 Hz) is strongly temperature dependent in the range from 200 °C up to 400 °C, making it useful for temperature evaluation. The temperature dependence was measured for the emission line at 617 nm; the results demonstrate that anatase doped europium(III) can be used as a thermographic phosphor. © 2009 Elsevier B.V. All rights reserved. Source

Eckert C.,University of Duisburg - Essen | Eckert C.,Center for Nanointegration Duisburg | Pflitsch C.,University of Duisburg - Essen | Pflitsch C.,Center for Nanointegration Duisburg | And 2 more authors.
Progress in Organic Coatings | Year: 2010

A promising method of measuring surface temperatures in harsh environments is the use of thermographic phosphor coatings. There, the surface temperature is evaluated from the phosphorescence decay lifetime following a pulsed laser or flash lamp light excitation. Depending on the used dopant, single doped M3+:α-Al2O3 (M = Cr, Dy, Tm) emit at 694 nm (Cr3+), 488 nm (Dy3+), 584 nm (Dy3+), and 459 nm (Tm3+), respectively. However, the accessible temperature range with a single dopant is limited: for the Cr3+-transition from 293 K up to 900 K, and for the Dy3+ and Tm3+-transitions both from 1073 K up to 1473 K. In the present study a new approach is followed to extend these limitations by co-doping two dopants using the sol-gel method and dip coating of α-Al2O3 thin films. For that application (Dy3+ + Cr3+) co-doped thin α-Al2O3 films and (Tm3+ + Cr3+) co-doped α-Al2O3 films with thicknesses of 4-6 μm were prepared, and the temperature-dependent luminescence properties (emission spectra and lifetimes) were analysed after pulsed laser excitation in the UV (355 nm). The phosphorescence lifetime as a function of temperature were measured between 293 K and 1473 K. A considerably extended range for surface temperature evaluation was established following this new approach by combining different dopants on the molecular level. © 2009 Elsevier B.V. All rights reserved. Source

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