Non-isothermal kinetics of thermal decomposition of NH4ZrH(PO4)2·H2O

Nanocrystalline NH 4 ZrH(PO 4 ) 2 ·H 2 O was synthesized by solid-state reaction at low heat using ZrOCl 2 ·8H 2 O and (NH 4 ) 2 HPO 4 as raw materials. X-ray powder diffraction analysis showed that NH 4 ZrH(PO 4 ) 2 ·H 2 O was a layered compound with an interlayer distance of 1.148 nm. The thermal decomposition of NH 4 ZrH(PO 4 ) 2 ·H 2 O experienced four steps, which involves the dehydration of the crystal water molecule, deamination, intramolecular dehydration of the protonated phosphate groups, and the formation of orthorhombic ZrP 2 O 7 . In the DTA curve, the three endothermic peaks and an exothermic peak, respectively, corresponding to the first three steps' mass losses of NH 4 ZrH(PO 4 ) 2 ·H 2 O and crystallization of ZrP 2 O 7 were observed. Based on Flynn–Wall–Ozawa equation and Kissinger equation, the average values of the activation energies associated with the NH 4 ZrH(PO 4 ) 2 ·H 2 O thermal decomposition and crystallization of ZrP 2 O 7 were determined to be 56.720 ± 13.1, 106.55 ± 6.28, 129.25 ± 4.32, and 521.90 kJ mol −1 , respectively. Dehydration of the crystal water of NH 4 ZrH(PO 4 ) 2 ·H 2 O could be due to multi-step reaction mechanisms: deamination of NH 4 ZrH(PO 4 ) 2 and intramolecular dehydration of the protonated phosphate groups from Zr(HPO 4 ) 2 are simple reaction mechanisms.