Electrical behaviour of monoclinic celsian derived from cation-exchanged commercial zeolites.

Monoclinic Celsian has been obtained by a not conventional way, i.e. the thermal treatment of 4A-type commercial zeolite, where a stechiometric amount of barium ions was inserted by means of a cation-exchange treatment. A small concentration of alkaline ions (either sodium or lithium) was 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 for the low-cost precursors, as well as for the low temperatures and times required. However, the presence of even a small concentration of alkaline ions and a residual amorphous phase can negatively affect the electrical 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 increse above 200°C.