Optical Study of Eu³⁺ Ion Embedded in (1-x)Na₂WO₄-xP₂O₅ Glasses Highlighting a Temperature Effect on its Local Environment

Tungsten-phosphate glasses doped with trivalent europium ion are synthesized and their spectroscopic proper-ties are analyzed. Following the evolution of the D-5(0) -> F-7(1) electronic transition in a series of various glass compositions via two rank crystal field parameters (cfp's), a slight modification of the local symmetry is evidenced in the series. Decay lifetimes of D-5(1) and D-5(0) levels are also analyzed. Optical properties clearly correspond to Eu3+ in the glassy phase. At room as well as at liquid nitrogen temperatures, the emission spectra display comparable features with prominent D-5(0) -> F-7(2) transition. However, at 77 K, the maximum F-7(1) splitting exhibits an increase of approximate to 20-23 % for all compounds. This increase is directly connected to a change in local environment around the rare earth ion. The optical properties and the crystal field variation could be correlated with the shortness of the metal-oxygen distances produced by the pressure when cooling.