document: The formulation in Table 1 was derived by an empirical approach and led to a non-classical glass matrix. Carter et al. [3] and Zhang et al. [4] took a more systematic approach to such glass-ceramic wasteforms. These wasteforms were targeted at Hanford K-basin sludges and the immobilisation of the primary waste stream from production of molybdenum-99 at the Australian Nuclear Science and Technology Organisation site in Sydney respectively. In the work of Carter et al. and Zhang et al. the intended crystalline phase was the closely related titanate pyrochlore, CaUTi2O7. The glass matrix was formulated such that the trivalent species in the glass network, boron and aluminium, were charge compensated on a molar basis by sodium. The stoichiometric composition of the glass in this wasteform was Na2AlBSi6O16. This glass provides a method by which the glass composition can be varied systematically. Given that the initial observations inferred an important role played by alumina, it was decided to prepare a suite of zirconolite glass-ceramics in which the glass matrix was defined by Na2Al1+xB1–xSi6O16 to investigate the role played by glass composition in controlling crystalline phase stability. The x=1 end member gives the mineral albite, NaAlSi3O8. The melting point of albite is 1120°C [5] and the composition cools to a glass at the cooling rates that occur during a HIP cycle. From the available phase diagrams, [6] no boron analogue for albite was shown, and the liquidus estimated from the relevant phase diagram is 1100–1200°C. No phase diagrams for the quaternary system Na2O–Al2O3–B2O3–SiO2 could be found.
extractive_keyphrases: albite alumina aluminium boron cauti2o7 crystalline glass na2albsi6o16 na2o–al2o3–b2o3–sio2 naalsi3o8 sodium titanate pyrochlore
abstractive_keyphrases: glass-ceramic wasteforms glass composition glass matrix glass network hanford k-basin sludges immobilisation of the primary waste stream from production of molybdenum-99 investigate the role played by glass composition in controlling crystalline phase stability mineral albite molybdenum-99 na2al1+xb1–xsi6o16 non-classical glass matrix zirconolite glass-ceramics