Yttrium-doped barium fluoride crystal and preparation method and use thereof
Disclosed are a yttrium-doped barium fluoride crystal and a preparation method and the use thereof, wherein the yttrium-doped barium fluoride crystal has a chemical composition of Ba (1−x) Y x F 2+x , in which 0.01≤x≤0.50. The yttrium-doped BaF 2 crystal of the present invention has improved scintillation performance. The yttrium doping may greatly suppress the slow luminescence component of the BaF 2 crystal and has an excellent fast/slow scintillation component ratio. The doped crystal is coupled to an optical detector to obtain a scintillation probe which is applicable to the fields of high time resolved measurement radiation such as high-energy physics, nuclear physics, ultrafast imaging and nuclear medicine imaging.
1. A method for preparing an yttrium-doped barium fluoride scintillation crystal having a chemical composition of Ba (1−x) Y x F 2+x , wherein 0.01≤x≤0.50, and the method comprises the steps of:
weighing and mixing raw materials of YF 3 and BaF 2 according to the molar ratio BaF 2 :YF 3 =(1−x): x to obtain a mixed powder, wherein 0.01≤x≤0.50;
putting the mixed raw materials into crucibles in a vacuum furnace for thorough melting at a temperature of 1200 to 1400° C., and then cooling the mixture to obtain Ba (1−x) Y x F 2+x polycrystalline material, or subjecting the mixed powder to isostatic pressing, and putting the resulting substance into crucibles and sintering it at 900 to 1200° C. in vacuum to obtain sintered Ba (1−x) Y x F 2+x polycrystalline material; and
mixing the resulting polycrystalline material with an appropriate amount of PbF 2 powder, which is act as a deoxidizer, and growing crystals by vertical Bridgman method;
wherein the processes of the vertical Bridgman method include:
maintaining the furnace in a vacuum degree of less than 10 −3 Pa, melting the Ba (1−x) Y x F 2+x polycrystalline material and PbF 2 powder at 1200 to 1400° C., subjecting the resulting melt to crystal growth wherein the descending speed of the crucible is 0.5 to 4 mm/hour, and cooling the grown crystal to room temperature at a temperature decreasing rate of 10 to 50° C./hour;
wherein the deoxidizer PbF 2 is added in an amount of 0.5 to 5 wt % of the Ba (1−x) Y x F 2+x polycrystalline material.
2. The method of claim 1 , wherein the crucibles are high purity graphite crucibles or glassy carbon crucibles.
3. The method of claim 1 , wherein the deoxidizer PbF 2 is added in an amount of 0.5 to 2 wt % of the Ba (1−x) Y x F 2+x polycrystalline material.
4. The method of claim 1 , wherein the isostatic pressing is performed at a pressure of 5 to 20 MPa for 0.1 to 1 hour.