中子辐照对6H-SiC晶体比热容的影响

EFFECT OF NEUTRON-IRRADIATION ON SPECIFIC HEAT CAPACITY OF 6H-SiC CRYSTAL

用剂量为8.2×1018/cm2的中子对6H-SiC晶体进行了辐照。采用X射线衍射仪、差示扫描量热仪测试6H-SiC晶体中辐照损伤。结果表明:中子辐照对6H-SiC样品产生了严重损伤,且辐照后的6H-SiC的比热容明显上升。对辐照样品进行了常温至1200℃的退火处理,退火后的辐照样品的比热容先随退火温度的升高而逐渐降低,1000℃时比热容到达最低值;当退火温度超过1000℃时晶体的比热容反而上升。运用从头算方法定性计算了晶体中间隙原子对比热容的影响。结果表明:晶体经中子辐照及退火后,其比热容发生变化的主要原因在于晶体中间隙原子的浓度的变化。辐照后的样品在超过1000℃退火时比热容的反常回升现象,极有可能与辐照前对晶体所作的在1000℃的预退火处理有关。

6H-SiC single crystals were neutron-irradiated up to a dose of 8.2 ×10^18/cm^2. The radiation damages in the single crystals were investigated by means of X-ray diffraction, differential scanning calorimeter and so on. It is found that there are serious damages in the neutron-irradiated 6H-SiC crystals. The specific heat capacity of the neutron-irradiated SiC crystals rises obviously. After annealing from the room temperature to 1 200 ℃ the specific heat capacity of the samples reduced with the annealing temperature rising The influence of interstitial atoms to the specific heat capacity was calculated quantitatively by the ab initio method. The results show that the increase of the specific capacity heat of the neutron-irradiated SiC crystals and its recovery on annealing are both caused by the exchanges of the interstitial atoms. The specific heat capacity of the irradiated SiC crystals at the temperature around 1 000 ℃ appears an abnormality phenomenon, which was probably related to the annealing of the crystals before neutron-irradiation.