Spectroscopic Characterisation Of Oxynitride Glasses In The System Mg-Ca-Si-Al-O-N

Oxynitride glasses in the system Mg-Ca-Si-Al-O-N possessing nitrogen contents of up to 7.2 wt% were prepared by calcining and melting a mixture of powdered oxidic glass and a preceramic polymeric precursor solution, yielding aluminium nitride by pyrolysis. The UV-VIS-NIR spectra of the glasses are influenced by spherical inclusions of elemental silicon but show a higher infrared transmittivity than the corresponding oxide glasses due to their low content of water. EPR studies revealed the existence of free or unpaired electrons in the glass structure caused by carbon radicals or by some unknown nitrogen containing co-ordination groups.