Compositional tailoring of structural and dielectric properties of La2MMnO6 (M=Ni, Cu & Zn) double perovskites: a comparative study

This comparative study analyzes crystallite size, strain, BET surface area, pore size, dielectric properties, and AC conductivity of double perovskite compositions: La2NiMnO6 (LNMO), La2CuMnO6 (LCMO), and La2ZnMnO6 (LZMO), synthesized via Sol–Gel Pechini route. X-ray diffraction confirmed monoclinic structures (P21/n). Williamson-Hall analysis showed LNMO with the smallest crystallite size (55.71 nm) and the highest strain (3.24 × 10−3), while LCMO has the largest size (64.22 nm) and the lowest strain (1.43 × 10−3). BET analysis indicated LZMO with the highest surface area (6.673m²/g), and LNMO with the smallest pore size (3.038nm). LCMO exhibited the highest dielectric constant, suggesting a strong potential for energy storage applications, with an inverse correlation between dielectric constant and BET surface area. However, the higher tangent loss for LNMO and LCMO limits their practical applications in low-loss devices. Impedance spectroscopy revealed non-Debye-like relaxation. LCMO also showed the highest AC conductivity, attributed to enhanced charge carrier hopping among Cu/Mn cations. The highest activation energy for LZMO aligns well with the lowest conductivity, highlighting its insulating and semiconducting applications. The study emphasizes the effects of transition metal cations at the M-site, providing a detailed comparison of the compositions.