Shinobu Nagahama

Long luminescent glass: Tb3+-activated ZnO–B2O–SiO2 glass

Abstract It has been found that zinc borosilicate glasses 60ZnO–20B 2 O 3 –20SiO 2 doped with 0.2 mol% Tb 2 O 3 exhibit phosphorescence after exciting with 254 nm light. This phosphorescence arises from f–f transitions of Tb 3+ ions and is observable by the eye, in the dark for up to 1 h after stopping the UV-illumination. Electron spin resonance (ESR) measurements show that electron trapping centers, associated with Zn ions, are formed by the UV irradiation and the phosphorescent centers decay after the irradiation was stopped. We suggest that this UV induced center is the photo-induced electron trap, which serves effectively as an electron donor, in the dark.

Formation of fluoride glasses based on AlF3YF3PbF2 system

Abstract A glass-forming region has been studied in the system of AlF3YF3PbF2. Colorless glasses, about 1 mm thick, have been prepared by quenching melts on a carbon plate. Upon replacing PbF2 by RF2, where R = Mg, Ca, Ba, or replacing YF3 by YbF3 in the ternary system, the glass thermal stability against crystallization is improved. Glasses with optimized composition are more stable than the well known AlF3YF3CaF2BaF2 glasses, and rods or disks have been prepared. The AlF3YF3PbF2-based fluoride glasses are characterized by a wide transmission window and higher chemical durability and mechanical strength than those in the ZrF4 system, and therefore are very promising for fiber or laser window material applications in the mid-infrared region.