Abstract: Based on material design idea, we employ a co-precipitation strategy to obtain sinterable Ho₂Zr₂O₇ fluorite particles, successfully leading to novel transparent Ho₂Zr₂O₇ ceramics with good optical/magneto-optical properties. The resulting precipitation precursor is identified to be hydrated basic carbonate upon calcination at the optimum temperature of 1250 °C into near-spherical Ho₂Zr₂O₇ nanopowder with an average size of ∼64 nm and unimodal narrow size distribution. The crystal intrinsic oxygen defect in fluorite ceramic generally exists in the form of F⁺ center. The best bulk specimen achieved in this work exhibits a high refractive index of ∼2.1 and a high transparency of ∼74.4% at 1000 nm comparable with the corresponding defect-free single crystal (∼76.4% in theory). In the Ho₂Zr₂O₇ structure system, the electronic polarizability of O^2- anion generally remains constant around 2.2 ų in the visible region and the corresponding optical basicity is approximately 0.9. The developed magneto-optical transparent Ho₂Zr₂O₇ ceramic has Verdet constants of -180 ± 3, -157 ± 5, -87 ± 2, -54 ± 2, and -43 ± 2 rad T^-1 m^-1 at 515, 635, 780, 980, and 1064 nm, respectively, which are roughly 1.2-fold higher than the commercial TGG crystal.

Key words: Transparent ceramics, Ho₂Zr₂O₇, Magneto-optical ceramics, Fluorite, Optical properties