Oxyfluoride silicate glasses and glass-ceramics doped with erbium and ytterbium - An examination of luminescence properties and up-conversion phenomena

Oxyfluoride glasses doped with erbium and ytterbium have been fabricated at T = 1460 °C. To prepare glass-ceramic systems, the precursor glasses were annealed at temperature 750 °C for 2 h. The ordered fluoride-like crystalline phases were recognized applying XRD, SAED and EDS methods. The spectroscopic properties of the glass-ceramic samples were significantly different as compared to those observed in the precursor glass. Particularly, the emission spectra of glass-ceramics are evidence that some of Er^{3 +} and Yb^{3 +} ions reside into the ordered environment. Up-conversion phenomena attributed to visible anti-stokes emission of Er^{3 +} has been observed under excitation of Yb^{3 +} ions by a 980 nm diode laser. Especially, the substantial enhancement of red up-converted luminescence was observed in the glass-ceramic system. Dissimilar spectral characteristic and relation of both aforementioned emissions examined in glass and glass-ceramic samples point at different contributions of processes relevant to up-conversion phenomena. The detailed analysis of the crucial Er^{3 +} and Yb^{3 +} excited states relaxation dynamics and their spectroscopic qualities has been performed to determine the mechanisms which lead to conversion of the infrared excitation into visible emission.