Non-isothermal kinetics study with isoconversional procedure and DAEM: Thermal decomposition of LaPO4:Ce,Tb·0.5H2O

The precursor, La0.9Ce0.05Tb0.05PO4·0.5H2O was synthesized via solid-state reaction at 333 K. The experimental results show that the synthesized product is orthorhombic La0.9Ce0.05Tb0.05PO4·0.5H2O, and monoclinic La0.9Ce0.05Tb0.05PO4 is a green emitting phosphor which can be obtained after calcining La0.9Ce0.05Tb0.05PO4·0.5H2O at 973 K in air. Based on the iterative isoconversional procedure, the values of activation energy Eα associated with the Region I and Region II of the thermal decomposition of the precursor were obtained, which demonstrates that the Region II is a kinetically complex process, and the Region I is a single-step kinetic process and can be described by a unique kinetic triplet [Eα, A and g(α)]. The most probable reaction mechanism of the Region I was estimated by the comparison between experimental plots and modeled results. The value of pre-exponential factor A of the Region I was obtained on the basis of Eα and the reaction mechanism. The distributed activation energy model (DAEM) was applied to study the Region II.