Transparent long lasting and photo-stimulating materiaals

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Long lasting luminescence(LLL)and photostimulated luminescence(PSL)were found in reduced calcium aluminate glasses activated with Tb3+ ions. The LLL from Tb3+ was observed by illuminating the Tb3+4f-5d charge transfer band with uv light, while the PSL was seen by stimulating the glasses after uv-illumination with 633nm light. The decay curve of the LLL was fitted with a second order kinetics for the initial period and a first order for the latter. An electron spin resonance signal which is attributed to an F+-like center associated with Ca^<2+> ions was induced by illumination with uv-light and its intensity decay was fitted with the latter component of the LLL.The appearance of the PSL by illumination with 633nm light distinct reduced the ESR signal intensity. The thermoluminescent spectra of the specimen illuminated at 77K were composed of two components peaking at 〜240K and 〜380K.The low temperature peak and the high temperature peak were attributed to an F-center(two electrons trapped at the site of an oxygen vacancy)and an F+-center(an electron trapped at the site of an oxygen vacancy), respectively. It was concluded from the above results that electrons of the F-center and the F+-center contribute predominantly to the emergence of the LLL and the PSL, respectively.