Structural characteristics and spectral properties of novel transparent lithium aluminosilicate glass-ceramics containing (Er,Yb)NbO4 nanocrystals

Transparent lithium aluminosilicate glass-ceramics based on nanosized crystals of β-quartz solid solutions and Er,Yb orthoniobates are prepared for the first time, to our knowledge. According to X-ray diffraction analysis, parent Er,Yb-codoped glass contains (Er,Yb)NbO4 nanocrystals with the defected fluorite structure while the single Yb-doped glass is X-ray amorphous. The Er,Yb orthoniobates with the tetragonal structure crystallize under heat-treatments at 800-900 °C; and at 1000 °C the transformation to a monoclinic form begins. β-quartz solid solutions are the main crystalline phase of glass-ceramics prepared in the temperature range of 800-1000 °C. These structural transformations are confirmed by Raman spectroscopy. The structure evolution is illustrated by the TEM study of the Yb-doped glass and glass-ceramics. The spectral-luminescent properties of glass-ceramics are directly linked to their structure; an appearance of the monoclinic phase has a crucial effect on these properties. Glass-ceramics with tetragonal (Er,Yb)NbO4 nanophase are characterized by the high efficiency of Yb3+→Er3+ energy transfer (85%), strong absorption in the vicinity of 0.98 μm and shorter lifetime of 4I13/2 state (as compared with the parent glass), so they look promising for laser operation in the eye-safe region around 1.53 μm.