Abstract
Dehydrated polycrystalline powder of LTA-type zeolite and its pellets, prepared from 7.86×10−2 to 1.5728GPa, were studied by XRD, SEM, BET and PALS. Crystal size, texture and changes in the inter-particle pellet volume were observed from XRD and SEM results, respectively, as the pellet pressure increased. Positron lifetime spectra of these zeolite samples consisted of four lifetime components (τi, Ii; i=1, 2, 3, 4), remaining practically constant each lifetime (τi) as the pellet pressure was varied, but their intensities were pressure dependent. The decreasing tendency of the inter-particle pellet volume can be followed by the mean lifetime τ124+τ1*I1+τ2*I2+τ4*I4, where the third lifetime component was practically pellet pressure independent. The third and fourth lifetime components (τ3, I3; τ4, I4) can be assigned to o-Ps annihilating in the dehydrated β and α cages of the zeolite, respectively, as inferred from the correlation between the calculated specific internal surface area of the zeolite and that obtained from PALS data, registered either form the 50 or 800ns instrumental windows.
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