Cation speciation, compactness, and structure‐property correlations in manganese aluminosilicate glasses

We report on the elastic properties of x MnO‐Al 2 O 3 ‐(6‐ x )SiO 2 manganese aluminosilicate glasses, in which pronounced exchange coupling and antiferromagnetic interaction occurs among the paramagnetic Mn 2+ ions. X‐ray absorption reveals a Mn‐O bond length of ∼2.1 Å, and a distance of ∼3 Å between Mn 2+ ions in sixfold coordination, further corroborated by electron paramagnetic resonance and dynamic photoluminescence spectroscopy. This indicates the presence of edge‐sharing MnO 6 units, in resemblance to edge‐sharing MnO 8 in the crystalline Spessartine garnet Mn 3 Al 2 [SiO 4 ] 3 . We argue that these cluster species have a profound effect on material stiffness: the compact structure of manganese aluminosilicate glasses enables a Young's modulus in the 100 GPa range and a Poisson's ratio of about 0.3. This exceeds the compositional trend with cation field strength observed for other aluminosilicate glasses.