Chemical Stabilization of β‐Cristobalite

Abstract

Chemically stabilized β‐cristobalite has been synthesized in the Na 2 O‐Al 2 O 3 ‐SiO 2 and CaO‐Al 2 O 3 ‐SiO 2 systems. Highly reactive chemical precursors in the gel and zeolitic state are thermally transformed to stabilized β‐cristobalite crystalline solutions in each system. High‐temperature X‐ray diffraction, phase data, differential scanning calorimetry, thermochemical analysis, electron microscopy, and magic‐angle spinning NMR give information on the limits of stability of β‐cristobalite, the α—β phase transition, thermal expansion behavior, and the structural state of the crystalline solutions.