Monoclinic celsian has been obtained by a non-conventional way, i.e. the thermal treatment of 4A-type commercial zeolite: a stoichiometric amount of barium ions was included in the zeolite by means of a cation-exchange treatment. A small concentration of alkali ions (either sodium or lithium) was also present in the exchanged zeolite, since previous studies had underlined the positive effect of these ions on the formation of monoclinic celsian. This particular synthesis proves to be economic, due to the low-cost precursors, the low temperatures and the short times required. However, the presence of even a small content of alkali ions and a residual amorphous phase can negatively affect the insulating properties of the material, thus hindering its use in electrical insulating systems. The results so far obtained show that the material keeps good insulating properties at low temperature, but its conductivity and dielectric losses strongly increase above 200 degrees C. (c) 2006 Springer Science + Business Media, Inc.