Inelastic X-ray Scattering Studies of Zeolite Collapse

In situ inelastic x-ray scattering (IXS) experiments have been used to probe heterogeneity and deformability in zeolte Y as this thermally collapses to a high density amorphous (HDA) aluminosilicate phase. The Landau-Placzek ratio R-LP falls slowly as amorphisation advances, increasing in the later stages of collapse clearly showing how homogeneity improves non-linearly - behaviour linked closely with the decline in molar volume V-Molar. The Brillouin frequency omega(Q) also decreases with amorphisation in a similar fashion, signifying a non-uniform decrease in the speed of sound nu(l). All of these changes with zeolite amorphisation infer formation of an intermediate low density amorphous (LDA) phase. This low entropy or "perfect glass" has mechanical properties which are closer to the zeolite rather to the HDA glass - notably a very small value of Poisson's Ratio signifying unusually low resistance to deformation.