High temperature and high pressure X-ray diffraction study of SAPO-37: effect of chemical composition on the mechanical properties of faujasite-type materials

Abstract

SAPO-37 with a faujasite-type structure was studied by X-ray diffraction at high temperature and high pressure. A similar degree of negative thermal expansion (NTE) was observed for SAPO-37 with respect to siliceous faujasite with α_{v(303–773 K)} = −10.7 × 10⁻⁶ K⁻¹. This similarity can be linked to the important role of oxygen displacement in proposed NTE mechanisms. SAPO-37 is more compressible than other faujasites, with a bulk modulus of 18(1) GPa. SAPO-37 also undergoes pressure-induced amorphisation at lower pressures. These results indicate that changes in chemical composition can strongly modify the stability and compressibility of the faujasite network.