Binary transparent (Ho1-xDyx)2O3 ceramics: Compositional influences on particle properties, sintering kinetics and Faraday magneto-optical effects

Abstract Binary transparent magneto-optical (Ho1-xDyx)2O3 (x = 0.01–1) ceramics derived from layered rare-earth hydroxide (LRH) compounds were fabricated by vacuum sintering. They have in-line transmittances of ∼67‒77 % at the visible wavelength of 700 nm and ∼77‒84 % at the mid-infrared wavelength of 5 μm with similar maximal infrared cut-off at ∼9.5 μm. The impacts of Dy3+ doping on particle properties, sintering kinetics and Faraday magneto-optical effects were systematically investigated. The results show that (1) The LRH precursors exhibit the nanosheet morphology with the thickness of ∼6‒10 nm. Dy3+ incorporation not only induces an expansion for the hydroxide host layer but also a contracted interlayer distance; (2) Upon calcination at 1100 °C, the LRH nanosheets collapse into sphere-like oxide particles. The addition of Dy3+ leads to increasing lattice constants and decreasing theoretical densities for the (Ho,Dy)2O3 solid solutions; (3) A smaller bandgap energy for Dy2O3 (∼4.85 eV) was obtained relative to those of (Ho0.9Dy0.1)2O3 (∼5.24 eV) and Ho2O3 (∼5.31 eV); (4) Dy3+ dopant promotes grain growth and the pure Dy2O3 bulk has a rather smaller grain-boundary-diffusion controlled activation energy (∼457 kJ/mol) than the (Ho0.9Dy0.1)2O3 counterpart (∼626 kJ/mol); (5) The Verdet constants of magneto-optical (Ho1-xDyx)2O3 ceramics generally linearly increase with the rise of Dy3+ concentration.