Preparation And Characteristics Of SrHfO₃ :Ce Scintillator Ceramics

Scintillators are widely used in the detection equipments of high energy physics, nuclear medicine and geological exploration areas as a photoelectric conversion device. Presently, the commonly used scintillation material is single crystal which needs high requirement for the equipment and has the long prepare period and high cost. Compared to single crystal, the polycrystalline scintillator ceramics is becoming a new research focus because of its low cost and good processing performance and its properties are easy to tailor. The performance of SrHfO₃:Ce transparent ceramic scintillator meets requirements of the CT scintillation material, and it has the merits of uniform doping compared with single crystal scintillator. How to prepare the excellent scintillation powders and how to determine the various parameters in ceramic sintering process are the key technologies which need to resolve during the preparation of SrHfO₃:Ce ceramic scintillator.The preparation technology and performance of SrHfO₃:Ce scintillation ceramic powders were studied in this paper emphatically as well as the technics of the sintering process. The sol-gel methods were used to prepare SrHfO₃:Ce nanopowders. The phase transformation, crystallization process, particle size, morphology, suitable experimental conditions and photoluminescence properties of the sample were characterized by XRD, TG-DTA, FTIR, SEM and PL.(1) SrHfO₃:Ce nanoparticles were prepared by sol-gel method. Results show that the high-performance powders can be received with the experimental condition of pH=5,initial concentration=0.10mol/L, sol temperature=80℃,drying temperature=130℃and calcining at 1000℃for 2h.There is a broad band spectrum which is from 200 to 340nm in the excitation spectra at the 385nm light, peaking at 218,242 and 308nm.There are three emission bands in the emission spectra excited by the 218nm light, peaking at 380,487 and 526nm, which is caused by 5d-4f transition of Ce3+. Luminescence properties of the powder are affected by the content of Ce. The luminous intensity reaches the maximum value when the content of Ce is 1.5%. When the atomic content of Ce is above 1.5%, the concentration quenching occurs which leads to the intensity of the characteristic peak decreased.(2) The green pressing was prepared by dry pressing method, and the ceramics samples were prepared by two-step sintering method in vacuum atmosphere. The effect of the parameters on the ceramics samples were explored in the pressing and sintering process. The results show that properly increasing the green pressing density is helpful to the sintering densification. When the relative density of the green pressing is 52%, a relative density of 94.2% can be reached after sintering. With the gradually increasing sintering temperature, the sample densification increases gradually. When the sintering temperature is 1680℃, the relative density of ceramics can reach 94.2%. When the atomic content of sintering additives Y2O3 is below 8%, the system is single-phase, and it can reduce the sintering temperature for 40℃and increase the relative density to 97.5% with the crystal grain size of the samples about 1μm. Due to the high crystallinity of the ceramic samples, the luminescence properties changes compared with the powder. The excitation and emission spectrums have only one broadband spectrum respectively, but still correspond to the luminescence properties of Ce3 + ions.