Revisiting the thermal decomposition of layered gamma-titanium phosphate and structural elucidation of its intermediate phases.
The thermal transformations of gamma-titanium phosphate, Ti(PO(4))(H(2)PO(4)) x 2 H(2)O, have been studied by thermal analyses (thermogravimetry (TG) and differential thermal analysis (DTA)) and variable-temperature (31)P magic-angle spinning (MAS)/CPMAS and 2D (31)P-(31)P spin-exchange NMR. The structure of this material has been refined from synchrotron powder X-ray diffraction data (monoclinic, P2(1), a = 5.1811(2) A, b = 6.3479(2) A, c = 23.725(2) A, beta = 102.57(1) degrees). Vyazovkin's model-free kinetic algorithms have been applied to determine the apparent activation energy to both dehydration and dehydroxylation of gamma-titanium phosphate. In these processes, several overlapped steps have been detected. Structural models for Ti(PO(4))(H(2)PO(4)) x H(2)O and Ti(PO(4))(H(2)P(2)O(7))(0.5) intermediate layered phases have been proposed.
García-Granda
Santiago
S
Departamento de Química Física y Analítica, Universidad de Oviedo, 33006 Oviedo, Spain.
Khainakov
Sergei A
SA
Espina
Aranzazu
A
García
José R
JR
Castro
Germán R
GR
Rocha
João
J
Mafra
Luís
L