Morphological study and thermal behaviour of an ammonium-titanium(IV) phosphate with pyrochlore-type structure

Polycrystalline ammonium-titanium(IV) phosphate with pyrochlore-type structure has been obtained under hydrothermal conditions and characterised by powder X-ray thermodiffractometry (HT-pXRD), electron microscopy (SEM and TEM) and thermal analysis (TG/SDTA–MS). Moreover, the activation energy of thermal decomposition has been calculated as a function of the extent of conversion applying the Vyazovkin isoconversional method to the thermogravimetric data. The sample is constituted by nearly spherical plate-like particles (diameter ca. 25 nm) which in an aqueous medium are prone to auto-assembling to originate polycrystalline fibres. Thermogravimetric analysis showed significant differences between the thermal decomposition behaviour in inert (N2) and oxidiser (O2) atmospheres (e.g. the total mass loss), revealing the presence of a fraction of P(III) which oxidises to P(V) when the N2 atmosphere is replaced at 823 K by O2 atmosphere.This work is supported by “Ministerio de Economía y Competitividad” (MAT2013-40950-R, MAT2011-27573-C04-02), “Gobierno del Principado de Asturias” (GRUPIN14-060) and FEDER.Peer reviewe