Perspectives on oxynitride glasses: Transparency, compositions, redox, composites, crystallization, and applications

Oxynitride glasses are glasses wherein two-fold oxygen atoms are substituted by three-fold nitrogen atoms. This results in increased physical and mechanical properties, which have long driven the development of such materials. This article examines the reactivity of oxynitride melts, with the aim of deepening our knowledge of the formation of oxynitride glasses, of the reasons for their opacity, and of the influence of the often-overlooked redox state. The functionalization of oxynitride glasses through the crystallization of oxynitride and nitride crystals, and by the control of the particles size of the precipitating metal and nitride species (from the nano- to the micro-scale), is also discussed in the light of recent advances in the fields of optical and photonic materials. Our main objective is to provide insights and a renewed momentum to this field by providing new guidelines for future fundamental and applied investigations. Graphical summary of the elaboration of glass-based materials from oxynitride glass-forming melts. This study investigates and highlights the reactivity of oxynitride glass-forming melts on the basis of Ellingham diagrams. The control of the chemistries and microstructures of glass-based materials – through appropriately defined compositional and experimental design, thereby enabling selective promotion of in-situ reactions – allows for the achievement of unique physicomechanical properties, hence opening up new avenues for their functionalization and practical application.