Dielectric investigations on ‘MgAlON’ compounds: role of nitrogen content

The dielectric properties of dense polycrystalline magnesium aluminium oxynitride have been investigated up to 90 °C. The oxygen/nitrogen substitution on the anionic lattice of this solid solution enhances the charge trapping ability and the dielectric breakdown of ‘MgAlON’ compounds. Oxygen vacancies, which play the role of electron traps, can partially explain the good dielectric properties of this solid solution at low temperature; but they are ineffective for higher temperature where the charge trapping phenomenon remains active. This behaviour, specific to ‘MgAlON’ solid solution, is explained on the basis of a crystallographic model of atom repartition: this spinel structure offers rich-nitrogen zones randomly located as AlN4 clusters which generate locally the heterogeneous zones of electric charge supposed to be responsible for the good dielectric performance of ‘MgAlON’ compounds. The local polarizability is modified which enhances the charge-trapping phenomenon.