Journal of the American Ceramic Society, Vol.100, No.12, 5433-5443, 2017
Sintering behavior of Ba/Sr celsian precursor obtained from zeolite-A by ion-exchange method
(Ba, Sr)-exchanged zeolite A with composition Ba0.74Sr0.22Na0.04Al2Si2O8 was prepared by cation exchange; a mild thermal treatment converts into an amorphous phase. Successive crystallization and sintering behavior was studied by XRD, DTA, and thermodilatometric analysis. The results point out the activation of viscous flow sintering mechanisms between 900 degrees C and 1050 degrees C. The densification process starts when the amorphous phase reaches its glass transition temperature (897 degrees C) and finishes when the material crystallizes forming hexacelsian. The application of an external pressure in such temperature range allows to achieve an almost complete densification, the material transforming at 1300 degrees C into dense monoclinic celsian much below the typical processing temperature.