Abstract
The temperature dependence of the structure of a polycrystalline sample of AgTaO3 has been determined using in-situ Synchrotron X-ray powder diffraction methods. This work finds no evidence for the presence of a monoclinic phase, rather three phase transitions have been identified, namely R3c <->(390 degrees C) Cmcm <-> (465 degrees C) P4/mbm <-> (580 degrees C) Pm (3) over barm. The rhombohedral phase was further studied at room temperature by neutron powder diffraction. The co-existence of the rhombohedral and orthorhombic phases around 380-400 degrees C indicates that the transition between these is first order, and gives rise to unusual peak shapes in the diffraction patterns.