| crystal, which exhibits excellent thermoluminescence (TL) and optically stimulated luminescence (OSL) properties, was widely used in radiation dosimetry (especially OSL dosimetry). At present, there are two problems with the crystal growth and research of α-Al2O3:C. Firstly, Czochralski (Cz) method was the only method used for α-Al2O3:C commercial crystal growth. Secondly, the mechanism of the carbon in improving the dosimetry properties of sapphire is still in disputed. However, few research reports have been found in our country so far.Considered the practical needs and problems of α-Al2O3:C crystal, the dissertation mainly carries out researches in the following two areas:(1) The preparation of crystal detector:α-Al2O3:C crystal of 450×120×10mm was grown by edge-defined film-fed grown technique(EFG) with a fast pulling rate. α-Al2O3:C crystal detector of 5×5×1 mm and a direction by directional cutting, grinding and polishing Using high purity graphite powder of 6N and high purity α-Al2O3 purity of 4N as raw materials,α-Al2O3:C crystal doping with 5000 ppm carbon were successfully grown by the EFG method. The influence of different types of radiation(β、241Am、137Cs、60Co) on the TL and OSL properties of α-Al2O3:C crystal were investigated. The results indicate that α-Al2O3:C crystal detector of our preparation measured 1μGy in China academy of sciences, was the world’s known highest accuracy; the α-Al2O3:C crystal with low energy of radiation shows the higher sensitivity of TL and OSL properties, was 3.5 times of LiF (Mg, Cu, P) of current widespread use; α-Al2O3:C crystal of high concentration of carbon doped (test of carbon content of greater than 5000ppm) TL peak at near 255°C (518K), TL peak shift to the direction of low temperature with the increase of radiation dose, as second order kinetics peak, α-Al2O3:C crystal of low concentration of carbon doped (test of carbon content of about 3000ppm) TL peak at near 190°C (463K), TL peak no change was found in the position with the increase of radiation dose, as first order kinetics peak; the lattice and trap energy of α-Al2O3:C crystal of high concentration of carbon doped changed. In the range of low dose, TL and OSL response curve of α-Al2O3:C crystals shows excellent linear characteristic with different radiation, TL sensitivity of the crystal irradiated with 241Am (58KeV) of low energy was three times of irradiated with 137Cs (660KeV) and 60Co (1025KeV), TL and OSL sensitivity of the crystal irradiated with 137Cs (660KeV) and 60Co (1025KeV) was very similar.(2) The preparation of ceramic detector:α-Al2O3:C ceramic was prepared using the vacuum sintering method for radiation dosimetry, α-Al2O3:C ceramics detector of 5×5×1 mm was obtained after cutting. The results indicate that α-Al2O3:C ceramic sinter at 1850°C had the optimal of TL and OSL properties, was 60% of α-Al2O3:C crystal.α-Al2O3:C ceramic of TL peak at near 200℃ (473K), TL peak no change was found in the position with the increase of radiation dose, as first order kinetics peak; The OSL decay curve of α-Al2O3:C ceramic showed an exponential attenuation, the early-fattenuation was fast with attenuation above 50% at 10s, but the rate of decay was slower than crystal of attenuation above 90% at 10s, while the late attenuation reduce; OSL intensity increased with the irradiation dose increased; In the range of low dose, TL and OSL response curve of α-Al2O3:C ceramic shows excellent linear characteristic with different radiation, TL sensitivity of the ceramic irradiated with 241Am (58KeV) of low energy was 2-2.5 times of irradiated with 137Cs (660KeV) and 60Co (1025KeV),TL and OSL sensitivity of the ceramic irradiated with 137Cs (660KeV) and 60Co (1025KeV) was very similar. The OSL properties of a-Al2O3:C ceramic was better than α-Al2O3:C crystal, and the preparation of α-Al2O3:C ceramic was simpler and faster than α-Al2O3:C crystal.α-Al2O3:C ceramic may have potential application in radiation dosimetry.Compared with the α-Al2O3:C crystal grown by the Cz method, large-sized α-Al2O3:C crystals doping with controllable amount of carbon can be grown by the EFG method, and EFG method can grow shaped α-Al203:C crystal with a fast pulling rate and low cost.α-Al2O3:C ceramic was prepared using the vacuum sintering method as a new dosimetry material, adopt ceramic process, can be sintered at temperatures below the melting point and can be easily implemented C doping at the same time, the production of low cost, high efficiency, high active ion doping concentration and can produce large size and complex shape samples, suitable for mass production. EFG method growth crystals need two days, and the vacuum sintering of α-Al2O3:C ceramics prepared by just about 36 hours. |
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