Abstract
Zircon-class ternary oxide compounds have an ideal chemical formula of ATO4, where A is commonly a lanthanide and an actinide, with T = As, P, Si, or V. Their structure (I41/amd) accommodatesa diverse chemistry on both A- and T-sites, giving rise to more than 17 mineral end-members of fivedifferent mineral groups, and in excess of 45 synthetic end-members. Because of their diverse chemicaland physical properties, the zircon structure-type materials are of interest to a wide variety of fieldsand may be used as ceramic nuclear waste forms and as aeronautical environmental barrier coatings,to name a couple. To support advancement of their applications, many studies have been dedicated tothe understanding of their structural and thermodynamic properties. The emphasis in this review willbe on recent advances in the structural and thermodynamic studies of zircon structure-type ceramics, including pure end-members [e.g., zircon (ZrSiO4), xenotime (YPO4)] and solid solutions [e.g.,ErxTh1–x(PO4)x(SiO4)1–x]. Specifically, we provide an overview on the crystal structure, its variationsand transformations in response to non-ambient stimuli (temperature, pressure, and radiation), and itscorrelation to thermophysical and thermochemical properties.