Spectroscopic Properties of Pr 3+ , Tm 3+ , and Ho 3+ in Germanate-Based Glass Systems Modified by TiO 2 .

In this paper, the effect of the GeO 2 :TiO 2 molar ratio in glass composition on the spectroscopic properties of germanate glasses was systematically investigated. The visible luminescence bands associated with characteristic 1 D 2 → 3 H 4 (red), 5 S 2 , 5 F 4 → 5 I 8 (green), and 1 D 2 → 3 F 4 (blue) transitions of Pr 3+ , Ho 3+ , and Tm 3+ ions in systems modified by TiO 2 were well observed, respectively. It was found that the luminescence intensity of glasses containing Pr 3+ and Ho 3+ ions increases, whereas, for Tm 3+ -doped systems, luminescence quenching with increasing content of TiO 2 was observed. Based on Commission Internationale de I'Eclairage (CIE) chromaticity coordinates (x, y) analysis, it was demonstrated that the value of chromaticity coordinates for all glasses depends on the GeO 2 :TiO 2 molar ratio. The addition of TiO 2 to system compositions doped with Tm 3+ ions shifts the (x, y) to the center of the CIE diagram. However, chromaticity coordinates evaluated for glasses containing Pr 3+ ions move to a purer red color. Our results confirm that the spectroscopic properties of the studied glasses strongly depend on TiO 2 content. Moreover, it can be stated that germanate-based glass systems modified by TiO 2 can be used for optoelectronics in RGB technology as red (Pr 3+ ), green (Ho 3+ ), and blue (Tm 3+ ) emitters.