Novel magneto-optical transparent Dy2Sn2O7 ceramics with pyrochlore structure for advanced optical ammeter technology

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 ų, optical basicity of ∼0.97, and an effective magnetic moment of ∼10.27μ_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.