Paulo J.R. Montes

Yttria thin films doped with rare earth for applications in radiation detectors and thermoluminescent dosimeters

Abstract Thin films of pure and Nd doped Y 2 O 3 were prepared following a new sol–gel route on glass substrate. Sets of thin films were prepared in different oxidation and densification conditions and the effect of such conditions in the morphology, crystallization, surface aspect and thermoluminescence (TL) and radioluminescence response are analysed. The results indicates that the films are suitable for scintillating devices rather than solid state TL dosimeters.

Influence of co-dopant in the europium reduction in SrAl2O4 host

Xerogels of strontium chlorate and aluminium chlorate doped with europium (un-co-doped) and co-doped with rare earth ions (Ln = Gd, Dy, Er and Y) were prepared using the proteic sol-gel route. Synchrotron radiation was used to investigate the effect of different co-dopants on the Eu(3+) → Eu(2+) reduction process during the synthesis of the samples. Samples were excited at the Eu LIII-edge and the XANES regions were analyzed. The results suggest that some of the Eu ions can be stabilized in the divalent state and that it is difficult to completely reduce Eu(3+) to Eu(2+) during thermal treatment. The mechanisms of the Eu reduction processes are explained by a proposed model based on the incorporation of charge-compensation defects.

The effect of the host composition on the lifetime decay properties of barium/strontium aluminates compounds

This paper reports the influence of the structural change on the luminescence of Eu-doped barium/strontium aluminates when excited with monochromatic X-rays (also known as X-ray excited optical luminescence—XEOL). Ba1−xSrxAl2O4 samples, with 0 < x < 1, were produced via proteic sol-gel route and it was observed that the XEOL emission spectra are composed by the Eu2+ and Eu3+ transitions, although no Eu2+ was observed in the X-ray absorption spectra. The XEOL intensities while the sample is under irradiation decreased as a function of the irradiation time, indicating the buildup of radiation damage. The saturation level of the XEOL is directly correlated to the amount of damages induced by the irradiation and the sample composition. The Ba-rich samples are the ones with higher XEOL yield. X-ray induced long lasting phosphorescence (LLP) was also observed for all samples and it was found that the duration of the phosphorescence emission also depends on the sample composition. In Sr-rich samples, the LLP has...