Further Investigation of the Stabilization of β‐Cristobalite

Chemical stabilization of β‐cristobalite has been achieved using two methods: (1) incorporating “stuffing” cations Na, Ca, Cu, and Sr into the cavities in the tectosilicate framework, as previously reported, and (2) without “stuffing” cations, by substituting AlPO 4 into the framework. XRD, TEM, FTIR, DSC, and solid‐state variable‐temperature 29 Si NMR confirm that stabilization occurs by both methods. Dynamic disorder, characteristic of the β‐cristobalite structure above the α↔β phase transition, was observed via TEM in the NaAlO 2 ‐, CaAl 2 O 4 ‐, and CuAl 2 O 4 ‐stabilized cristobalites at room temperature. For AlPO 4 ‐stabilized material intergrowths of AlPO 4 regions with a tridymite‐type structure suppress the β‐ ↔α‐cristobalite phase transition.