Preparation And Characteristic Of BaHfO₃:Ce³⁺ Ceramic Scintillator Powders By Sol-Gel Process

BaHfO3:Ce3+ polycrystalline ceramic scintillating material of the main photoelectric conversion device is widely used in the detection equipments of high energy physics, nuclear medicine and geological exploration areas as a main photoelectric conversion device. The synthesis of excellent scintillation powders is the key technology need to resolve during the preparing of ceramic scintilltor. Ppreparation process and performance of BaHfO3:Ce3+ scintillation ceramic were studied systematically in this paper.Citric acid and EDTA were used as the chelating agent. BaHfO3:Ce3+ powders were synthesized by sol-gel method. The characteristics of the samples such as phase transformation, crystallization process, particle size, morphologies and photoluminescence properties were characterized by FT-IR, XRD, TG-DTA, SEM, PL, and etc.Gelation is transparent under the condition of Citric acid was used as the chelating agent, initiate concentration is 0.10 mol/L, pH value is 3.6, CA:EG=1:3, and calcined at 1050℃for 2 hrs, BaHfO3:Ce3+ nano-powders are formed. the powders have high degree of crystallinity and are near-spherical with the uniform granularity of about 30 nm. Using EDTA as the chelating agent, at the initial concentration is 0.08mol/L, pH value is 9, and EDTA:EG=1:1, we got the gelation, which was aging 12 hrs and ultrasonic dispersing, then calcined in 900℃for 2 hrs, we got the powders, the size of which is even and near-spherical, the grain diameter of which is about 30 nm. Analysis shows doping different amount Ce3+ resulted in the behavior of solid solution belonged to interstitial-type defects and substitution-type defects, lattice parameters of BaHfO3 was changed, but the doping of Ce3+ doesn't change the crystal structure of BaHfO3.The maximum luminous intensity of excitation spectra and emission spectra appeared at dopping of 0.9 mol%Ce3+(molar fraction). Two excitation bands are excited by the 530 nm light which peaking at 393 nm in the violet part and 445 nm in the blue part.The Emission spectra excited by 393 nm light has two excitation bands as well as it is excited by 445 nm light, peaking at 530 nm and 590nm. The emission character is resulting from the 5d→2F5/2 and5d→2F7/2 transitions of Ce3+ cation. The illumination intensity of the powders prepared by citric acid as complexing agent is slightly stronger than that by EDTA as complexing agent.Spherical nanometer powders with good dispersibility and even grain diameter could be made by using these two complexing agents. Because of the stability of EDTA complex compounds, which has a five-membered ring structure, molecule of the complex compound does not have condensation polymerization but cross bonding between hydrogen bonds. When use the EDTA as the complexing agent, the calcined temperature is 250℃lower than the temperature when use the citric acid as the complexing agent.