GUEST-GUEST INTERACTION AND PHASE-TRANSITIONS IN THE NATURAL ZEOLITE LAUMONTITE

The zeolite water arrangement in laumontite Ca3.85Na0.23K0.06Al7.96Si16.03O48.nH(2)O (n = 16-18) and leonhardite (n = 12-14.4) has been studied from H-1 and Al-27-NMR data at temperatures of 200-390 K. Close agreement is found between NMR data obtained for samples n = 12 and n = 18 and previous X-ray and neutron diffraction data. The H2O arrangement in the powder sample with n = 14.4 and in a laumontite single crystal is represented by a combination of the H2O arrangements in samples with n = 12 and n = 18 with increased orientational H2O disordering. Concentration-type phase transitions are found in the single crystal and the n = 16 and n = 18 samples at 226 and 230 K, and orientational-type phase transitions are found in the sample with n = 14.4 at 230 K, and in the sample with n = 18 at 293 K. The smooth transformations into an orientationally disordered glassy state arrangement of H2O in the zeolite channels is found in samples with n = 14.4, 16, and 18 at 300-330 and 305-315 K.