Cs2TiNb6O18 is a potential ceramic wasteform for the long-term immobilization of radioactive cesium. Cs2TiNb6O18 was synthesized using the aqueous precursor method and a solid-state reaction, and its crystal structure was determined from the Rietveld refinement of synchrotron X-ray and neutron powder diffraction data. The structure is a pyrochlore analogue, space group P3̅m1 with Cs in 9-fold coordination. The calculated bond valence sum from analysis of neutron diffraction data of 0.84 and high coordination number suggest that Cs has a strong bonding environment. The chemical aqueous durability was investigated using the MCC-1 and PCT-B standard test methods. The measured Cs leach rates of 3.8 × 10–3 and 2.1 × 10–3 g m–2 day–1 obtained via the MCC-1 and PCT-B methods, respectively, demonstrate good promise of a safe long-term immobilization material comparable to, if not better than, hollandite—the material in the multiphase titanate ceramics (Synroc) targeted for cesium sequestration.

Variable-temperature powder X-ray diffraction studies have been used to monitor dramatic changes in the thermal expansion properties of zeolites with the LTA topology on changing the pore contents. Detailed structural analysis was performed on dehydrated Li-, Na-, K-, Rb-, and Cs-exchanged zeolite A and a comparison made with their purely siliceous analogue ITQ-29. Mean thermal expansion coefficients were also determined for the hydrated alkali-metal-exchanged forms. Thermal expansion behavior ranging from negative to positive was observed as different monovalent cations were included in the zeolite pores. Cation-induced strain to the zeolite framework has been shown to play a significant role in the thermal expansion mechanism of LTA-zeolites. Atomic-scale mechanisms behind the thermal expansion behavior have been deduced for ITQ-29, dehydrated Ag-A, and dehydrated Na-A systems.

X-Ray powder diffraction studies have been used to measure the thermal expansion properties of three zeolites with the LTA topology and provide details of the underlying structural changes. Siliceous ITQ-29 and dehydrated and hydrated silver zeolite A have large negative, moderate negative and positive thermal expansion coefficients, respectively.

The simultaneous application of high pressure and high temperature has been used to achieve direct ion exchange of large cesium cations for the small sodium cations found in the zeolite natrolite by putting it into a superhydrated state with increased pore size. The larger cations remain trapped upon pressure release, and thus, this method is a means of producing new cationic forms of zeolites.

Crystalline metal (IV) phosphates with variable zirconium-to-titanium molar ratios of general formula (Ti1−xZrx)(HPO4)2·H2O have been prepared by precipitation of soluble salts of the metals with phosphoric acid and heating the amorphous solids in 12 M H3PO4 in an autoclave. The new materials are structurally characterised by Rietveld analysis of synchrotron X-ray powder diffraction data and pair distribution function (PDF) analysis of high energy synchrotron X-ray total scattering data. A broad range of zirconium–titanium phosphate solid solutions were formed showing isomorphous substitution of titanium by zirconium in the α-titanium phosphate lattice and vice versa for titanium substitution into the α-zirconium phosphate lattice. In both cases the solubility is partial with the coexistence of two substituted phases observed in samples with nominal compositions between the solubility limits.Layered phosphates of general formula (Ti1−xZrx)(HPO4)·H2O have been prepared by the hydrothermal treatment of amorphous gels in phosphoric acid and characterised by Rietveld analysis of high resolution synchrotron X-ray powder diffraction data and pair distribution function analysis of high energy synchrotron X-ray total scattering data.

Pair distribution function studies using X-ray scattering data from zeolite Na-A samples treated at pressure up to 8 GPa indicate a pressure-induced amorphisation mechanism involving loss of crystallographic order of the aluminosilicate framework but retention of the local sodium to oxygen bonding.

The tetracationic water soluble compound 5,10,15,20-tetrakis(N-methyl-4-pyridyl)porphyrin, [H2-TMPyP]4+, has been directly incorporated, during the hydrothermal synthesis, into the nanopores of two zeolites, namely X and Y, and the aluminophosphate VPI-5 framework. The resulting solids were characterised by a combination of X-ray powder diffraction, thermal gravimetric analysis and UV–Vis spectroscopy. The implications for the use of these and related porphyrins as structure directing agents are discussed.

X-Ray powder diffraction studies have been used to measure the thermal expansion properties of three zeolites with the LTA topology and provide details of the underlying structural changes. Siliceous ITQ-29 and dehydrated and hydrated silver zeolite A have large negative, moderate negative and positive thermal expansion coefficients, respectively.

Pair distribution function studies using X-ray scattering data from zeolite Na-A samples treated at pressure up to 8 GPa indicate a pressure-induced amorphisation mechanism involving loss of crystallographic order of the aluminosilicate framework but retention of the local sodium to oxygen bonding.