Doped yttrium iron garnet materials exhibit semiconducting behavior and have potential applications in resistive-based sensors, including thermoresistive and gas sensors. In this study, we synthesized Ni-doped yttrium iron garnet samples using the sol-gel method combined with heat treatment. The crystal structure, morphology, and Ni incorporation into the crystal lattice were investigated using X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Raman spectroscopy. The saturation magnetization of the samples in the ground state was measured in a Physical Property Measurement System (PPMS) at 5 K. The experimental magnetic moments deviate significantly from the values calculated based on the cation distribution models, suggesting the occupation of Ni2+ and Fe2+ at the octahedral and tetrahedral sites, respectively, with the latter due to oxygen vacancies. We investigated the resistivity, magnetoresistance effect, and hydrogen sensing properties to elucidate the conduction mechanism. At room temperature, the resistivity of the samples decreased sharply as the oxygen vacancy concentration increased, from ∼108 Ωcm in sample x = 0 to ∼106 Ωcm in sample x = 0.08. The resistance of the samples increased when exposed to hydrogen gas, supporting the prediction from the magnetization data that the samples exhibit n-type semiconductor characteristics. The samples showed good sensitivity to H2 gas. At 250°C, sample x = 0.08 exhibits a response of S =11.5, the response time (τres. ∼8 s), and recovery time (τrec. ∼22 s) at 100 ppm hydrogen concentration.
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