Synthesis and electrophysical characterization of a three-phase Ca-Nd-Mn-Ni-O oxide system

The three-phase Ca-Nd-Mn-Ni-O oxide system was synthesized by a conventional solid-state ceramic method. The phase composition was investigated by X-ray diffraction (XRD) analysis using the PDF-5+/Rigaku SmartLab Studio II software package and was further confirmed by Rietveld refinement employing the GSAS-II software suite. According to the WPPF/Rietveld refinement results, the synthesized material predominantly consists of the Nd₀.₂₅Ca₁.₇₅MnO₄ phase (67.2 wt%), together with the perovskite-like Ca₀.₅Nd₀.₅Mn₀.₉₇Ni₀.₀₃O₃ phase (25.6 wt%) and a minor (Ni₀.₉₄Mn₀.₀₆)O phase (7.2 wt%). SEM analysis revealed an agglomerated granular morphology with porous regions, while elemental mapping confirmed the presence of Ca, Nd, Mn, Ni, and O in the synthesized material. FTIR spectroscopy showed characteristic metal-oxygen vibrational bands associated with [MnO₆] and [NiO₆] octahedral units. The electrical properties were investigated in the temperature range of 293-483 K at a frequency of 1 kHz. The material exhibited semiconducting behavior, and the calculated activation energies of electrical conduction were found to be 0.49 and 0.56 eV for the temperature intervals of 293-353 K and 393-483 K, respectively.