An Overview of the Structure and Properties of Silicon‐Based Oxynitride Glasses

Abstract

The silicon oxynitride glasses take advantage of nitrogen bonding to attain high elastic modulus, increased softening temperatures and viscosities, greater slow crack growth resistance, and modest gains in fracture resistance. Of the oxynitride glasses, the Si–Y–Al‐based oxynitride glasses have been most extensively studied and a degree of success has been achieved in understanding how changes in glass composition affect structural parameters and their relationship with properties. More recent studies have focused on the Si–RE–Me oxynitride glasses, where Me is primarily Al or Mg and rare earth (RE) includes most of the lanthanide series elements. These glasses possess a range of elastic, thermal, mechanical, and optical properties, which can be correlated with the strength of the RE bond in terms of the cationic field strength. However, such correlations require knowledge of not only the RE valence state but also its coordination with the anions. Herein, the current state‐of‐the‐art understanding of the properties and structural parameters of oxynitride glasses and their interrelationships are reviewed.

Crystallization pathways and some properties of lithium disilicate oxynitride glasses

“…It is known that incorporation of nitrogen into any oxide glass network affects the glass properties considerably [23][24][25][26][27][28][29][30][31][32]. Most properties change in the direction that is expected from the increase in the connectivity of the glass network.…”

“…Studies over the last decades have shown that addition of nitrogen to oxide glasses significantly affects their physical, chemical, mechanical, optical, and thermal properties [23][24][25][26][27]; however, information on the crystallization kinetics and on oxynitride glass-ceramics is scarce. For instance, the glass transition and crystallization temperatures, the elastic moduli, and the lithium mobility increase [28] whereas the thermal 4 expansion coefficient decreases [29][30].…”

Synthesis, mechanical and thermal properties of a damage tolerant ceramic: β-Lu2Si2O7

“…In addition, the elastic stiffness of ␤-Lu 2 Si 2 O 7 is higher than that of ␥-Y 2 Si 2 O 7 and ␤-Yb 2 Si 2 O 7 , which may be caused by the stronger bond of Lu O than Y O. Cation field strength (CFS) can be used to represent bond strengths of rare earth silicates. Hampshire proposed that the CFS can be calculated by: CFS = Z c /r c 2 , where Z c is ionic charge of the cation and r c is ionic radius of cation [24,25]. The ionic radius of the lanthanides decreases with increasing atomic number [19,20].…”

Synthesis and high-temperature creep behavior of a SiLuOC-based glass-ceramic

“…From their results, the glass-transition temperature of SiYAlON glasses (56Si28Y16Al oxynitride glasses) was found to be in the range of 870 to 950°C, depending on their nitrogen content. 30) In the system 56.5Si44La0.5Y20N80O a maximum glass-transition temperature of around 1020°C was determined. 30) This is significantly lower than the glass-transition temperature for SiLuOC (1291°C) determined here, which will have an impact on the densification behavior of Si 3 N 4 powders and consequently an external pressure during the sintering process should be necessary.…”

“…30) In the system 56.5Si44La0.5Y20N80O a maximum glass-transition temperature of around 1020°C was determined. 30) This is significantly lower than the glass-transition temperature for SiLuOC (1291°C) determined here, which will have an impact on the densification behavior of Si 3 N 4 powders and consequently an external pressure during the sintering process should be necessary. A high viscosity of the liquid melt during sintering however provides ¢-Si 3 N 4 particles with high aspect-ratio and improved fracture toughness of the resulting ceramic.…”