Structural deformation mechanisms of zeolites under pressure

The HP behavior of the natural zeolite yugawaralite and of the synthetic zeolite Na-A was studiedby in situ synchrotron X-ray powder diffraction, using a non-penetrating P-transmitting medium. Theunit-cell parameters of yugawaralite were refined up to the pressure of 10 GPa, at which reductionswere found of about 7, 2.4, 7, 1.3, and 15% for a, b, c, b, and V, respectively. Contractions of 6.5 and18.4% were found for a and V, respectively, for zeolite Na-A in the range 10–4 to 6.8 GPa. Diffractionpatterns collected during decompression show that the effects induced by high pressure on both samplesare almost completely reversible. These results are compared with those obtained under similar experimentalconditions for other natural zeolites, with the aim of rationalizing the deformation mechanismsof these porous materials and comparing their flexibility under high-pressure and high-temperatureconditions.