The oxynitrides are a group of inorganic compounds containing oxygen and nitrogen not bound to each other, instead combined with other non-metallic or metallic elements.
Some of these compounds do not have a fixed oxygen to nitrogen ratio, but instead form ceramics with a range of compositions.
With higher temperatures and pressures nitrogen can be heated with a mixed oxide to yield a product.
[1] Other nitrogen rich compounds that can be heated with oxygen containing material are urea and melamine.
For example urea heated with ammonium dihydrogen phosphate yields a phosphorus oxynitride.