The influence of alkali ions size on the superbroadband NIR emission from bismuth-doped alkali aluminoborophosphsilicate glasses

Glasses with compositions of 34.5SiO2–25AlPO4–12.5Al2O3–12.5B2O3–15R2O–0.5Bi2O3 (R = Li, Na, K) were synthesized. Characteristic absorption bands of bismuth centered at 500, 700, and 800 nm and broadband near infrared (NIR) emissions peaked at 1100 and 1300 nm were observed. With the change of alkali ion (Li+ → Na+ → K+), the intensity of absorption bands at 500 and 800 nm increase, while the intensity of two NIR emissions decrease. The dependence of NIR emission peaked at 1300 nm on the radius of the alkali ion is found to be opposite to that in previous reports, being ascribed to the abnormal reduction of Bi ion in the glasses investigated herein. The results of this work is helpful for understanding the nature of Bi-NIR-emission, and the NIR emission peaked at 1300 nm was proposed to originate from Bi+ according to the influence of the alkali ions sizes.

► NIR emission from Bi-doped aluminophosphsilicate glasses increase with increase in alkali ion radius.
► Tetrahedral anion groups in glass host can stabilize low valent Bi ions.
► NIR emission at 1300 nm was proposed from Bi+ according to the charge and the radius of alkali ion.