My doubt is lied to the fact that in a multilayered nanometric solid structure, subjected to annealing, there are a lot of concomitant reactions, whose temperature dependence can be different (e.g. nucleation and growth of new phases) and the method TTSP assumes Ea constant in the considered (usually 100-200 °C) range. The problem is exactly if assumption of the order is applicable in solid kinetic studies.
The degradation might be complex, nevertheless, there might be a dominant component, maybe resulting in "first-order-like" behaviour.
I would recommend to assume a reaction order and try whether your data fits an Arrhenius plot. If you get a linear plot, postulate your assumption true.