ENHANCING THE ELECTRICAL AND PHOTOCURRENT PERFORMANCE OF YIG NANOPARTICLES VIA Ca AND Zn CO-DOPING

Abstract

Y2.94Ca0.06Fe4.94Zn0.06O12 nanoparticles were successfully synthesized using the sol-gel method followed by annealing at 1000°C. X-ray diffraction (XRD) confirmed the formation of a single-phase garnet structure with an average crystallite size of 54 nm and a slightly expanded lattice constant (a = 12.395 Å). Detailed Raman and FTIR spectroscopy investigations revealed site-selective doping, where Ca2+ and Zn2+ ions substitute for Y3+ at dodecahedral sites and Fe3+ at tetrahedral sites, respectively, inducing localized lattice strain and modifications in Fe-O bond stiffness. Electrical characterization demonstrated a transition from an insulating to a semiconducting state, exhibiting a Negative Temperature Coefficient (NTC) behavior, with resistance decreasing from 223.9 KΩ at 300 K to 3.6 KΩ at 550 K. This conduction is governed by a small-polaron hopping mechanism between mixed-valence iron ions (Fe2+↔Fe3+↔Fe4+) characterized by a low activation energy of approximately Ea = 0.212 eV. The sample showed a broad-spectrum photo-response (218–1010 nm). Under an applied bias of 5 VDC, a peak photocurrent exceeding 44 µA was recorded at 593 nm, yielding a responsivity of 0.0178 A/W.