Further Investigation of the Stabilization of β‐Cristobalite

Abstract

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 AlPO4 into the framework. XRD, TEM, FTIR, DSC, and solid‐state variable‐temperature 29Si 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 NaAlO2‐, CaAl2O4‐, and CuAl2O4‐stabilized cristobalites at room temperature. For AlPO4‐stabilized material intergrowths of AlPO4 regions with a tridymite‐type structure suppress the β‐ ↔α‐cristobalite phase transition.