Effect of Gd and Cu on the Structural, Electrical, and Dielectric Properties of MnFeO3 Nanomaterials Synthesized 
by the Sol–Gel Method
Substituted GdxMn1−xFe1−yCuyO3 (x = 0.0–1.0; y = 0.0–0.5) nanoparticles were synthesized by sol–gel auto-combustion, and the effect of Gd and Cu content on their structural, electrical, and dielectric properties was investigated. X-ray diffraction data confirmed formation of an orthorhombic single phase with crystallite size in the range 23–61 nm. Particle size was determined by scanning electron microscopy. Direct current electrical resistivity and activation energy were observed to increase from 2.14 × 107  to 7.46 × 1010 Ω cm and from 0.64 to 0.70 eV, respectively, with increasing substituent concentration, whereas drift mobility decreased from 3.27 × 10−13 to 1.19 × 10−16 cm2 V−1 S−1. Dielectric constant, dielectric loss, and dielectric loss factor decreased with increasing frequency and with increasing Gd and Cu content. These decreases in dielectric properties with increasing electrical resistivity suggest the materials could be used in microwave devices.