Introduction Gadolinium oxysulfide (Gd2O2S, GOS) scintillation ceramics as luminescent materials are widely used in nuclear medical imaging and security inspections due to their high light output, low afterglow, and strong X-ray stopping capability. However, the synthesis process of GOS powder is intricately complex, having some challenges for achieving accurate component ratios and controlling the second-phase impurities, thus leading to difficulties in producing high-quality GOS scintillation ceramics. In this paper, GOS precursor powders were firstly synthesized by a hot water bath reduction method with sub-micron and nano-scale gadolinium oxide (Gd2O3) as raw materials, and Gd2O2S:Pr scintillation ceramics were subsequently prepared by a two-step sintering method (i.e., atmospheric pressure pre-sintering and HIP post-treatment). In addition, the microstructure and optical properties of the powder and ceramics were also characterized.Methods Gd2O2S:Pr phosphors were synthesized by a hot water bath reduction method. Gd2O3 (99.999%, Ganzhou Berier New Materials Co., Ltd., China), Pr6O11 (99.995%, Ganzhou Berier New Materials Co., Ltd., China), and concentrated H2SO4 (AR, Shanghai Macklin Biochemical Co., Ltd., China) were used as high-quality raw materials. Gd2O3 and Pr6O11 were firstly weighed according to (Gd1-xPrx)2O2S (x=0.001-0.010), and then mixed with a diluted sulfuric acid solution at a molar ratio of Gd2O3:H2SO4 of 1:1. The suspension was stirred and uniformed by a magnetic stirrer. Also, the suspension was heated in a hot water bath at 90 ℃ for 150 min. After the reaction was completed, the suspension was cooled to room temperature, and then the suspension was filtered, washed/dried, ground and sieved. Finally, the ground powders were calcined in a tube furnace, The resulting mixture was subsequently calcined in a tube furnace under a 20% hydrogen-nitrogen mixture reduction atmosphere at 750 ℃for 6 h to yield the gadolinium oxide sulfide powders.The Gd2O2S:Pr powders obtained were formed in a 15 mm cylindrical mold under uniaxial dry pressing at 10 MPa and then treated by cold isostatic pressing (CIP) at 200 MPa. Subsequently, the green bodies were pre-sintered in a flowing hydrogen-nitrogen atmosphere at 1 350 ℃ for 2 h, and HIP post-treatment was performed in argon at 1 600 ℃ and 180 MPa for 2 h. The sintered ceramics were polished and annealed for coming characterizations.Results and discussion The microstructure of Gd2O2S:Pr powders prepared with submicron-sized particles of Gd2O3 and nano-sized particles of Gd2O3 was examined, respectively. The results reveal differences in particle size and morphology between the two powders. Gd2O2S:Pr powder derived from submicron-sized Gd2O3 powder has irregular columnar particles and sheet-like structures, whereas that prepared with nano-sized Gd2O3 powder is coralloid particles. The fluorescence emission spectrum of the ceramics is consistent with that of the powders although the excitation peak partially obscures by the absorption peak. High-temperature sintering gradually eliminates the differences in particle size and leads to the formation of dense sintered bodies in the ceramics. Consequently, the discrepancy in fluorescence intensity caused by differences in particle size is reduced. Specifically, ceramics prepared with Gd2O3 nano-powder display a low fluorescence intensity, while those produced with Gd2O3 submicron-sized powder exhibites a high fluorescence intensity. To further investigate the factors influencing the optical properties of the ceramics, the doping concentration of Pr3+ was explored. Fluorescence and XEL spectroscopy tests were conducted on Gd2O2S:xPr (x=0.1%, 0.2%, 0.4%, 0.6%, 0.8%, and 1.0%) ceramics prepared using Gd2O3 submicron-sized powder with different Pr3+ doping concentrations. The experimental results reveal that the fluorescence and XEL spectral intensities reach their maximum values when the Pr3+ doping concentration is 0.2%. The SEM images demonstrate that the ceramics prepared using submicron-sized Gd2O3 powder have a dense structure with well-defined grain boundaries and uniform grain sizes. The EDS element distribution results confirm the effective doping of Pr element into the host lattice. Gd2O2S:Pr ceramic prepared exhibits a high transmittance.Conclusions The utilization of Gd2O3 submicron-sized powder resulted in Gd2O2S:Pr powder and the scintillation ceramics displayed a higher fluorescence intensity, compared to that synthesized with Gd2O3 nano-sized powder. Furthermore, Gd2O2S scintillation ceramics pre-sintered in a weak reducing atmosphere and subsequently sintered in a hot isostatic pressing exhibited improved density and optical properties. The maximum fluorescence intensity of the scintillation ceramics was achieved at a Pr3+ doping concentration x of 0.2%. In addition, the scintillation ceramics achieved a transmittance of 31% at a wavelength of 513 nm. This study developed a simple and cost-effective ceramic preparation process without any byproduct pollution, thereby offering a promising potential for large-scale production of high-performance Gd2O2S scintillation ceramics.