Composition–structure–property relationships of transparent Ca–Al–Si–O–N oxynitride glasses: The roles of nitrogen and aluminum

Abstract

We explore the formation and composition-structure-property correlations of transparent Ca-Al-Si-O-N glasses, which were prepared by a standard meltquenching technique using AlN as the nitrogen source and incorporating up to 8 at.% of N. Their measured physical properties of density, molar volume, compactness, refractive index, and hardness-along with the Young, shear, and bulk elastic moduli-depended roughly linearly on the N content. These effects are attributed primarily to the improved glass-network cross-linking from N compared to O, rather than the formation of higher-coordination AlO 5 and AlO 6 groups, where 27 Al magic-angle-spinning nuclear magnetic resonance experimentation revealed that aluminum is predominately present in tetrahedral coordination as AlO 4 units. Yet, several physical properties, such as the refractive index along with the bulk, shear, and Young's elastic moduli, increase concomitantly with the Al content of the glass. We discuss the incompletely understood mechanical-property boosting role of Al as observed both herein and in previous reports on oxynitride glasses, moreover suggesting glass-composition domains that are likely to offer optimal mechanical properties.

Elucidating photoluminescent properties of Eu‐doped Ca–Al–Si–O(–N) glasses and the local structures of Eu ions

“…Pristine oxide and oxynitride glasses before the addition of Eu 2 O 3 are referred to as E0 and NE0, respectively, as described in a previous study. 21 The cation compositions were estimated for comparing the glasses before and after remelting. The Si content in the mother glasses is marginally higher than that in the Eu-doped glasses, whereas the Ca and Al con-tents are lower owing to different analytical calculation methods for pristine glasses (EDX) and remelted glasses with Eu (ICP-OES).…”

“…The analyzed glass compositions are listed in Table 1. Pristine oxide and oxynitride glasses before the addition of Eu 2 O 3 are referred to as E0 and NE0, respectively, as described in a previous study 21 . The cation compositions were estimated for comparing the glasses before and after remelting.…”

“…The preparation of the pristine glasses was carried out using a previously reported procedure. 21 The pristine glass was crushed into a powder in an Al 2 O 3 mortar and mixed with an appropriate amount of Eu 2 O 3 powder. The mixed powders were remelted in Nb crucibles at approximately 1700 • C for 1 h using a radiofrequency furnace under the N 2 atmosphere.…”

“…An oxide glass, E0, was prepared from SiO 2 , Al 2 O 3 , and CaO, reagents, and an oxynitride glass, NE0, was prepared using the same oxides and AlN, which was partially added as a nitrogen source instead of Al 2 O 3 . The preparation of the pristine glasses was carried out using a previously reported procedure 21 . The pristine glass was crushed into a powder in an Al 2 O 3 mortar and mixed with an appropriate amount of Eu 2 O 3 powder.…”

“…Recently, one of the authors of this manuscript successfully obtained transparent and large Ca-Al-Si-O-N glasses with high N content via the melting process. 21 Therefore, oxynitride glasses prepared via the melting process can potentially be used as host materials doped with Eu ions for transparent phosphors.…”