Thorium(IV) phosphate-triphosphate: A valuable ceramic material obtained by thermal treatment of a layered ammonium-thorium(IV) phosphate. Kinetic analysis of the transformation.

Morphological and structural characterization of both (NH 4 ) 2 Th(PO 4 ) 2 ·H 2 O ( 1 ) and Th 2 (PO 4 )(P 3 O 10 ) ( 2 ) have been performed by using electron microscopy techniques (SEM, HR-TEM, DF-STEM and SAED), which reveal a morphological transformation from star-shaped particles to irregularly rhombohedral-like aggregates after thermal treatment at 1000 °C. The 1 → 2 thermal conversion is monitored by thermogravimetric analysis and the activation energy has been obtained by using isoconversional methods. A discrete model describing the kinetic process is obtained and so the original data set can be reconstructed and compared with the experimental measures. By using heating rates different from those involved for getting the model, predictions can be also made. The procedure has worked efficiently in recovering the original kinetic parameters in two theoretical simulations. [ABSTRACT FROM AUTHOR]