Transparent lutetia ceramics doped by rare earth cations

A novel wet chemical approach to prepare rare-earth (Re=Eu³⁺) doped Lu₂O₃ phosphor powder, as well as the fabrication of transparent lutetia-based ceramics were investigated. Co-precipitation processing was adopted to prepare nanosized Eu³⁺ doped lutetia powders with a spherical morphology and good sinterability using ammonium hydroxide (NH₃H₂O) and ammonium hydrogen carbonate (NH₄HCO₃) as the mixed precipitant. The thermal decomposition and phase evolution processes of precipitate precursor were investigated by Fourier transform infrared spectroscopy, thermogravimetry-differential thermal analysis-mass spectrometry, X-ray diffraction, and transmission electron microscope analysis. After calcination under the proper conditions, the resultant Lu₂O₃ phosphor powders exhibited a well-dispersed and near-spherical morphology with primary grain sizes of about 30-40 nm and a specific surface area of about 18 m²/g. Highly transparent polycrystalline Eu³⁺ doped Lu₂O₃ ceramics were fabricated by pressureless sintering under flowing H₂ atmosphere, the relative density of specimens could theoretically reach up to 99.8%, with grain sizes of about 50-60 μm after being sintered at 1850°C for 6 h. Optical linear transmittance in the visible wavelength region for 5% Eu:Lu₂O₃ ceramics (I mm in thickness) could reach as high as above 80% and produced a very strong emission peak at a wavelength of 610 nm under excitation of ultraviolet pulse. The luminescence behaviors of transparent lutetia ceramics indicated that they were promising detection materials and have potential for application in radiation detection and digital X-ray imaging.