Temperature-induced phase transformations of the small-pore zirconosilicate Na2ZrSi2O7.H2O

DTA-TG and powder XRD analyses are used to study the thermal behavior and the occurring upon heating structural transformations of the small-pore zirconosilicate Na2ZrSi2O7·H2O. Upon heating the monoclinic structure of the title compound converts into orthorhombic one, however preserving the initial topology. The heating above 800 °C leads to gradual distortion of the Si2O7 pyrogroups configuration and causes transformation of the [M2T6] into [M2T4] composite building units (CBUs) and irreversible transition of the orthorhombic compound into a phase with denser triclinic structure.