Spectroscopic properties of chromium/antimony co-doped alkali-alumina-borate glass-ceramics

Alkali-alumina-borate glass-ceramics co-doped with Cr and Sb ions are synthesized by the melt quenching technique. LiAl7B4O17 nanocrystals are formed in the glass host during the two-stage heat treatment at the crystallization temperature. For the samples of the initial and heat-treated glass with high antimony oxide content (>0.05 wt%), absorption spectra contain two absorption bands that are shifted to the short-wave region after the heat treatment. Initial and heat-treated glass with low antimony oxide content (<0.05 wt%) demonstrate two additional intense absorption bands centered at 255 and 355 nm, that are attributed to hexavalent chromium ions. The photoluminescence spectra possess three intense bands located at 685, 700, and 715 nm, and several wide structureless bands. The glass-ceramics luminescence excitation spectra consist of two bands centered at 390 and 540 nm, the intensity of the former increases with antimony content. The luminescence decay kinetics is described by the sum of two exponentials with decay times of 0.5-0.9; 5.5-7 ms respectively. The glass-ceramics luminescence quantum yield increases together with the antimony content (at a constant concentration of chromium) up to 35% at 2 wt% Sb2O3. Thus, it is possible to use the Cr/Sb co-doped glass-ceramics as phosphors in greenhouse light sources that generate near-IR spectral radiation necessary for the productive plant growth and development.