Preparation And Properties Of Strontium Hafnates Scintillating Ceramics

Scintillator is a kind of functional material which can convert incident high-energy rays or particles into ultraviolet or visible light.In recent years,with the development and popularization of medical imaging equipment such as PET and CT,and the establishment and renewal of large and fast electromagnetic calorimeter in high energy physics,detectors put forward more and more stringent requirements for scintillators,such as high light output,fast decay,high radiation resistance and low cost.Therefore,exploring and optimizing new scintillators is still an urgent task for materials scientists at present and in the future,and scintillation ceramics with their unique preparation advantages and good scintillation properties have become a hot research topic in recent years.SrHfO₃:Ce ceramics have relatively high density,high effective atomic number(p=7.56 g/cm³,Z_eff=64),fast decay time of about 42 ns,emission peaks of about 400nm can match well with silicon photodiodes,and ceramics have high theoretical light yield?40000 ph/MeV?and excellent time resolution?276 ps?,which are considered as representatives of the new generation of scintillators.In the past ten years,it has received wide attention.Firstly,Ce:SrHfO₃,Ce/Al:SrHfO₃,Ce/Al/Mg:SrHfO₃ and Ce/Y:SrHfO₃ ceramics were prepared by solid state method combined with vacuum sintering.The experimental results show that Ce/Al:SrHfO₃ ceramics have excellent scintillation properties,and the light yield is about 5700ph/MeV,which is also the highest at present.At the same time,it is found that different doping ions play different roles.Alumina acts as sintering additives,eliminating grain pore and promoting grain growth.The addition of yttrium oxide inhibits grain growth and plays the role of grain refinement,but the ceramics prepared by vacuum sintering contain a large number of intergranular pore,resulting in a low permeability of ceramics.Later,Ce:SrHfO₃ ceramics were prepared by vacuum hot pressing process.The use of carbon-containing dies resulted in serious carbon pollution.Although carbon can be eliminated by air annealing,the production of Ce⁴⁺resulted in the reduction of luminescent properties?XEL?.In order to avoid carbon pollution,Ce_0.005/Y_0.005:Sr_0.995Hf_0.995O₃ ceramics were prepared by vacuum pre-sintering and HIP post-treatment.The effects of pre-sintering temperature on the microstructure and spectral properties of ceramics were studied,but the transmittance of ceramics was low.In the later stage,Ce_0.005/Y_0.015:Sr_0.995Hf_0.995O₃ceramics with high transmittance were prepared by component optimization.The transmittance reached 49%at 800 nm.At the same time,under X-ray excitation,Ce_0.005/Y_0.015:Sr_0.995Hf_0.995O₃ ceramics have better luminescent properties than BGO crystals.The light yield of Ce_0.005/Y_0.015:Sr_0.995Hf_0.995O₃ ceramics is about 3500 ph/MeV under the excitation of ¹³⁷Cs radiation source.