Spectroscopic characterisation of oxynitride glasses in the system Mg-Ca-Si-Al-O-N

Oxynitride glasses in the system Mg-Ca-Al-Si-O-N possessing nitrogen conten ts of up to 7-2 wt% were prepared by calcining and melting a mixture of pow dered oxidic glass anti a preceramic polymeric precursor solution, yielding aluminium nitride by pyrolysis. The UV-VIS-NIR VIS-NIR spectra of the glas ses 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 office or unpaired electrons in the glass structure caused by carbon radicals or by s ome unknown nitrogen containing coordination groups. In the infrared spectr a the main bands are modified by the growing nitrogen content, evidences fo r Si-N as well as at Al-N bonds were obtained. XP spectroscopy, proved the presence of Si-N bonds and the existence of noncrosslinking nitrogen at hig h nitrogen concentration. AlO4-xNx tetrahedra with x=1, 2 were detected by Al-27 AIAS NMR spectroscopy.