We also conducted a thorough PXRD analysis (Figure and) to gain insight into the crystalline nature of Class I and II fibers. Both fiber classes, across all FRRs, exhibit low crystallinity and display broad peaks at lower 2θ ≈ 11°. This limited crystallinity along with the impurities from Htrz in some of the samples (see below) make it challenging to discern whether polymorph I or II of [Fe(Htrz)₂(trz)]BF₄ has been obtained. However, as with the synthesis of SCO particles, the definition and peak ratio of the double peak at 2θ ≈ 11° can be an acceptable indicator of the major presence of one of the two polymorphs. Thus, we conclude that the SCO composite fibers are a mixture of [Fe(Htrz)₂(trz)]BF₄ polymorphs I and II. Furthermore, even with the low crystallinity presented by Class I and II fibers across the different FRRs, some curious trends can be observed. In Class I fibers, a progressive shift from a phase mixture containing more polymorph I to a different phase mixture containing more polymorph II can be seen as the FRR increases from 0.5 to 9 (Figure ). This is evidenced by the main double peak at 2θ ≈ 11°, which gradually evolves into a single broad peak, signaling a shift toward a phase mixture containing more polymorph II. In addition, as the FRR increases from 4 to 9, the triple peak at 2θ ≈ 25° diminishes and eventually forms a double peak, further indicating this polymorphic transition. Interestingly, this transition is observed exclusively in Class I fibers prepared at FRRs of 4 and 9the only samples in which Fe(II) is present above the stoichiometric ratio relative to Htrz. This suggests that the Htrz shortage results in a [Fe(Htrz)₂(trz)]BF₄ phase mixture with an increased proportion of polymorph II, supporting our previous observation in the SCO particles. On the other hand, such evolution is not noticed in the main double peak at 2θ ≈ 11° for Class II fibers across all FRRs, suggesting that in all these fibers the excess of Htrz induces the formation of a phase mixture containing more polymorph I (Figure ).