Fantastic valence impacts of Pr on microstructures and Faraday magneto-optical effects of transparent (Ho,Pr)2O3 ceramics

Polycrystalline magneto-optical (Ho1-xPrx)(2)O-3 & nbsp;(x & nbsp;= 0.05-0.2) ceramics were fabricated by vacuum & nbsp;sintering & nbsp;using layered rare-earth hydroxides as the precursors, among which the 5 at.% Pr doped specimen exhibits the highest in-line transmittance of similar to 76.1 % at 700 nm (similar to 94.5 % of the theoretical value of defect-free Ho2O3 & nbsp;single crystal) and the largest Verdet constant of & minus;82 +/- 6 rad center dot T-& minus;1 & nbsp;m(& minus;1)& nbsp;at 1064 nm (similar to 2.3 times that of the commercial Tb3Ga5O12 & nbsp;crystal and similar to 1.8 times that of the pure Ho2O3 & nbsp;ceramic). More Pr addition not only leads to a higher thermal decomposition temperature for the precursor but also a decreasing particle size for the oxide. A 5 at.% Pr & nbsp;dopant & nbsp;in Ho2O3 & nbsp;matrix generally exists in the oxidation state of +3, while an increasing Pr concentration up to 10 at.% induces coexisting valences of +3 and +4. The grain growth was suppressed by the present Pr4+& nbsp;based on interstitial mechanism. The substitution of Pr3+& nbsp;for Ho3+& nbsp;is helpful for the rising Verdet constant of the binary ceramic, but Pr4+& nbsp;has little positive contribution to it.