Structure and fluorescence properties of ternary aluminosilicate glasses doped with samarium and europium

Abstract

Various ternary aluminosilicate glasses with the molar compositions 20 Al₂O₃–60 SiO₂–20 R₂O (R = Li or Na), 20 Al₂O₃–60 SiO₂–20 RO (R = Mg, Ca or Zn) and 23.1 Al₂O₃–69.2 SiO₂–7.7 R₂O₃ (R = Y or La) doped with 1 × 10²⁰ Sm³⁺ cm⁻³ or 1 × 10²⁰ Eu³⁺ cm⁻³ (about 0.2 mol% Sm₂O₃ or Eu₂O₃) were prepared. The glasses were studied with respect to their molecular structure, and their thermo-mechanical and fluorescence properties. All glasses show relatively broad fluorescence excitation and only a weak effect of the glass composition on the emission spectra is observed. Although the glasses should be structurally very similar, huge differences are found in the coefficients of thermal expansion and the glass transition temperatures. The fluorescence lifetime increases steadily with decreasing mean atomic weight and decreasing refractive index of the glasses, which may be explained by local field effects. The only exception from this rule is the zinc aluminosilicate glass, which shows a relatively high fluorescence lifetime. The highest fluorescence lifetime is found for the lithium aluminosilicate glass. The lowest coefficients of thermal expansion are found for zinc- and magnesium aluminosilicate glasses. A low coefficient of thermal expansion is a prerequisite for a high thermal shock resistance of the material and hence favorable for high-power laser applications.