Precise diffraction studies of temperature-dependent as well as composition induced structural phase transitions

As part of an ARC-funded project involving precise diffraction studies of compositionally and/or temperature induced structural phase changes, coupled electron, X-ray and neutron diffraction studies of composition as well as temperature induced structural phase changes in the NiGe1–xPx, Ni3±xIn1-yTe2+y and Ba4-xSrxNaSb3O12 systems have been carried out. Wide range non-stoichiometric solid solutions of average B8 structural type have been identified in the NiGe1–xPx, and Ni3±xIn1–yTe2+y systems and their (3+1)-d incommensurately modulated structures determined at several distinct compositions. The mechanism allowing compositional flexibility has thereby been identified in both cases. In the 1:3 ordered perovskite Ba4-xSrxNaSb3O12 system, diffraction studies have revealed a complex series of temperature and composition dependent phase transitions associated with ordering of the Na and Sb cations on the perovskite B site as well as with octahedral tilting.