Abstract: Eu:(Gd,Lu)₂O₃ ceramics possess high density, high effective atomic number, and high light yield, making them well-suited for high-energy ray imaging applications. To investigate the effect of Gd³⁺ doping concentration on the microstructure and optical properties of the ceramics, 5%Eu:Gd_xLu_1.9-xO₃ (5% is in atomic percent) nano-powders with different Gd³⁺ contents (x=0, 0.3, 0.6, 0.9, 1.2) were synthesized via co-precipitation. All powders exhibited a pure cubic phase, with the lattice constant increasing from 1.0391 nm to 1.0709 nm as the Gd³⁺ doping concentration increased. After vacuum pre-sintering at 1625 ℃ for 4 h followed by hot isostatic pressing (HIP) at 1700 ℃ for 3 h under 200 MPa Ar atmosphere, the relative densities of all ceramics exceeded 99%. The optical transmittance of 5%Eu:Gd_xLu_1.9-xO₃ ceramics first increased and then decreased with increasing Gd³⁺ content; the sample with x=0.6 achieved transmittances of 75.8% at 800 nm and 73.2% at 611 nm. The photoluminescence (PL) and X-ray excited luminescence (XEL) intensities of the 5%Eu:Gd_xLu_1.9-xO₃ ceramics first increased and then decreased with increasing Gd³⁺ content, while the fluorescence lifetime decreased from 1.26  ms to 0.90  ms, attributed to the migration of Eu³⁺ to low-symmetry C₂ sites. The sample with x=0.6 exhibited the highest PL and XEL intensities. In terms of radiation resistance, the XEL intensity of the x=0.6 sample decreased by approximately 5% after continuous X-ray irradiation for 20 min, while that of the Lu-based ceramic (5%Eu:Lu_1.9-xO₃ decreased by about 22%, indicating that the introduction of an appropriate amount of Gd³⁺ can significantly enhance the radiation stability of the material. All the ceramics with different compositions exhibit intense red emission (⁵D₀→⁷F₂, 612 nm) under both visible-light and X-ray excitation, which matches well with the spectral response of silicon photodiodes.

Key words: transparent ceramics, scintillation ceramics, microstructure, luminescence properties