*3.2. SEM Analysis*

For all samples, the autocombustion method with final annealing up to 1200 ◦C yielded a distribution of agglomerates about (~200–500 nm) that form a series of interconnected chains, as typical found in autocombustion synthesis [4]. In Figure 2a–q, the RSx series shows similar morphologies as those obtained by Zhang et al. [4,14]. In all of them, the notorious polycrystalline nature can be observed. The STEM images and elemental analyses given by yellow, red, blue, and green colors (Figure 2d–m) show the evolution of the systems when the Fe concentration increases. The systematic formation of the Fesubstituted YCrO3 phase is noted in the EDS pattern given in Figure 2r, and the atomic percentage contribution is summarized in Table 1. We can roughly say that the particles produced by this combustion method have a similar morphology and similar dispersion in all tested concentrations. In addition, considering the uncertainties of the element contents in the samples, we can also affirm that Y and O are quite constant, while Fe increases and Cr decreases its contribution; this indicates that Fe enters the crystalline cell, due to the larger ionic radius of Fe3+ (0.645 А˘ ) (compared to Cr3+ = 0.615 А˘ ), which is consistent with the unit cell volume determined from X-ray and neutron diffractions, as previously discussed.

**Figure 2.** (**a**–**c**) SEM images for the RS1, RS3, and RS7 samples (bar length = 1 μm). The magnified area was performed in high resolution mode, and the elemental mapping area for each sample is given in (**d**–**m**) images. SEM images for the RS2, RS4, RS5, and RS6 samples (**n**–**q**) (bar length =10 μm). (**r**) The EDS for the RS1–RS7 samples.


