Glass Formation and Structure–Property–Composition Relations of the RE ₂ O ₃ –Al ₂ O ₃ –SiO ₂ (RE=La, Y, Lu, Sc) Systems

Abstract

We report the glass‐forming regions of the ternary Lu 2 O 3 –Al 2 O 3 –SiO 2 and Sc 2 O 3 –Al 2 O 3 –SiO 2 systems. The density, molar volume, compactness, Vickers hardness, refractive index, as well as the glass transition ( T g ) and crystallization temperature are compared for two series of RE–Al–Si–O (RE=La, Y, Lu, Sc) glasses that display a constant molar ratio n Al / n Si =1.00, whereas n RE / n Si is equal to either 0.62 or 0.94. Several glass properties scale roughly linearly with the cation field strength (CFS) of the rare‐earth (RE 3+ ) ion, except for the T g values of the Sc‐bearing glasses that are significantly lower than expected. Magic‐angle spinning 29 Si and 27 Al nuclear magnetic resonance (NMR) reveal enhanced network disorder and increased relative populations of AlO 5 and AlO 6 polyhedra in the aluminosilicate glasses for increasing RE 3+ CFS, but overall similar Si and Al local environments (chemical shifts and quadrupolar couplings) in all samples associated with a constant n RE / n Si ratio, except for unexpectedly shielded 29 Si NMR signals observed from the Sc–Al–Si–O glasses.