Structural characterization of La0.7-xAxCa0.3MnO3 (A = Nd, Sm, Gd; x = 0.0, 0.1) manganites with rare-earth ions substitution

In this study, the structural properties of polycrystalline La0.7-xAxCa0.3MnO3 (A = Nd, Sm, Gd; x = 0.0, 0.1) manganites samples were systematically investigated. The samples were synthesized using a conventional solid-state reaction method, which involved precise weighing, thorough grinding, calcination, pelletization, and high-temperature sintering. X-ray diffraction analysis confirmed that all samples crystallize in a single-phase orthorhombic perovskite structure, corresponding to the Pnma space group, with no detectable secondary phases or impurities. Substitution of trivalent rare-earth ions Nd3+, Sm3+, and Gd3+ at the La3+ site led to a reduction in lattice parameters and unit cell volume compared to the undoped La0.7Ca0.3MnO3 sample. This decrease is attributed to the smaller ionic radii of Nd3+, Sm3+, and Gd3+ relative to La3+. Fourier-transform infrared spectroscopy revealed the characteristic Mn-O stretching vibration around 600 cm-1, confirming the perovskite bonding environment. Scanning electron microscopy analysis indicated inhomogeneous grain distribution in the La0.7Ca0.3MnO3 sample, whereas substitution with rare-earth ions resulted in a more uniform grain morphology. Energy-dispersive X-ray spectroscopy further verified the elemental composition of La, Ca, Mn, O, Nd, Sm, and Gd, demonstrating successful incorporation of the dopants. These results indicate that structural modifications induced by rare-earth substitution can effectively tune the lattice characteristics of La0.7-xAxCa0.3MnO3 manganites, which may have significant implications for their potential applications in magnetic, electronic, and spintronic devices.