Abstract: Designing a novel magneto-optical material with a low-cost substance and a large Verdet constant offers a better opportunity for state-of-the-art ammeter technologies. In this work, we pioneer the development of magneto-optical transparent Dy₂Sn₂O₇ ceramics via facile oxygen-atmosphere-controlled sintering for the first time. Detailed experimental studies and first-principles calculations are performed to provide significant insights into structural, optical, magnetic, and magneto-optical properties. Dy₂Sn₂O₇ crystallizes in the cubic pyrochlore structure. The Dy-O bond pertains to the ionic bond and the Sn-O bond belongs to the covalent bond, where the chemical bond stability increases in the order Dy-O (1) < Dy-O (2) < Sn-O (1) . The highest-performing Dy₂Sn₂O₇ bulk specimen exhibits a high in-line transmittance of ∼ 72.0 % at 635 nm ( ∼ 91.1 % of the theoretical transmittance), a fine average grain size of ∼ 3.1 μm, a high refractive index of ∼ 2.0, an oxygen ion polarizability of ∼ 2.39 ˚A³, optical basicity of ∼ 0.97, and an effective magnetic moment of ∼ 10.27 μ_B. The magneto-optical transparent Dy₂Sn₂O₇ ceramic has high Verdet constants of -199 ± 2, -154 ± 1, -107 ± 3, and -48 ± 1 rad T^-1 m^-1 at 515, 635, 780, and 1064 nm, respectively, which are ∼ 1.2-fold higher than the commercial Tb₃Ga₅O₁₂ single crystal. The ammeter we designed, using the new transparent Dy₂Sn₂O₇ ceramic as an optical current sensor, achieves the highest reported sensitivity of 3.121 ° /A at 635 nm to date, with no other results surpassing this value. Especially, our optical ammeter technology also shows the potential for use in extreme conditions. Our research fruits provide a beneficial reference on design, preparation, and application in advanced optical current transducers.

Key words: Dy₂Sn₂O₇, Current sensors, Transparent ceramics, Magneto-optical effect, Ammeter technology