Sintering behaviour of celsian based ceramics obtained from the thermal conversion of (Ba, Sr)-exchanged zeolite A

Five different samples of (Ba, Sr)-exchanged zeolite A, exhibiting the same Na residual content within the experimental error, were prepared by cation exchange. These powders, with or without a previous thermal treatment, were cold pressed in an isostatic press to manufacture cylindrical compacts. Such compacts were subjected to various thermal cycles up to 1500◦C. The sintering and densification of these compacts was studied by determining linear shrinkages, mass variation, bulk density and porosity. All the compacts produced were totally composed by BaAl2Si2O8–SrAl2Si2O8 solid solutions occurring in the polymorph known as monoclinic celsian. Porosity lower than 0.1% and bulk density higher than 95% theoretical density were obtained. The problems arising in the sintering of compacts manufactured with zeolitic precursor are discussed and proper measures to solve them are suggested