*3.2. FTIR Spectra*

Figure 4 shows the spectra for the compound of NdMnO3 doped with Bi in the frequency range from 450 cm<sup>−</sup>1–2000 cm<sup>−</sup>1. From this figure, we can see that the most significant absorption bands are located at the range of 600 cm<sup>−</sup>1–550 cm<sup>−</sup>1. The absorption bands at this range correspond to the Mn–O stretching vibration, linked to the internal movement of a length change of the bounds Mn–O–Mn, associated with the octahedron MnO6 attributed to a vibration characteristics of the perovskite-type ABO3 [3,19]. The absorption peak band at the range of 600 cm<sup>−</sup>1–550 cm<sup>−</sup><sup>1</sup> seem to shift towards lower wave number values for a structure having lower symmetry with decreasing Bi3<sup>+</sup> ion content, according to the increase of eg electrons in the anti-bonding orbital. Hence, the bond order would decrease with an increase in the number of eg electrons. The lower frequency band can be related to a higher deformation mode of the MnO6 octahedron [20,21]. The FTIR spectra confirm the formation of the NdBiMnO3 sample.

**Figure 4.** Fourier transform infrared spectroscopy (FTIR) spectra of Nd1−<sup>x</sup>BixMnO3 (x = 0, 0.25 and 0.50).
