Most radiation detectors, employed in x-ray radiography, consist of a
scintillator/phosphor screen coupled to an optical detector (photographic emulsion
film, photocathode, photodiode, etc.) [1]–[5]. Currently the most preferred phosphors
are Gd2O2S:Tb and CsI:Tl. Gd2O2S:Tb has been proven very useful in conventional
radiography screen-film systems. However, in digital radiography systems, based on
crystalline silicon (Si) optical detectors (CCDs, photodiodes) the green light emitted
by terbium-activated phosphors is not very efficiently detected [3], [6], [7]. This is
because a large number of Si based devices, incorporated in X-ray imaging systems
are not adequately sensitive to these wavelengths (500-550 nm) [3]. Since most Si
based photodetectors are more sensitive in the red wavelength range, it would be of
interest to investigate the emission efficiency of red emitting phosphors [6], [7].
For this purpose, europium (Eu)-activated phosphors, emitting at wavelengths
towards the red region of the light spectrum could be used instead of green emitting