铁磷熔体的氧化还原态和导电性能

ELECTRICAL PROPERTY AND REDOX STATE IN IRON PHOSPHATE MELTS

用电导率电池测量了含钠铁磷模拟放射性核废料 (HLW )熔体的电阻率 ,并分析了相应玻璃的M ssbauer谱 ,计算了铁离子的价态和氧化还原比 ,分析了温度、时间和氧化钠含量对熔体电阻率和玻璃氧化还原比的影响 .结果发现 :在Na2 O含量低的熔体中 ,升温和降温过程的电阻率的变化是不可逆的 ;随着Na2 O含量增加 ,不可逆性消失 ,熔体的电阻率随时间轻微下降 .同时发现 :Na2 O含量低的铁磷熔体的导电机理是电子性的 ,并用氧化还原比解释了其电阻率 -温度曲线的不可逆性 .铁磷模拟HLW熔体的电阻率类似于相近Na2 O含量的钠铁磷系统熔体的电阻率 .

The electrical resistivity of iron phosphate melts and high level radioactive waste (HLW) melts simulated by iron phosphate was measured at 1 223—1 723 K. The electrical resistivity cell was setup according to the standard 4 electrodes method. The Mssbauer spectra of the corresponding glass were obtained by ASA600 spectrometer at room temperature. The redox ratio of iron ions was calculated from the absorption envelope area. In iron phosphate melts with low soda content, the temperature dependent electrical resistivity displays irreversibility during the heating and cooling cycle. In iron phosphate melts with high soda concentration, the temperature dependent electrical resistivity is found reversible during the first heating and cooling cycle. The irreversibility decreases with increasing soda content. The electrical resistivity of the binary iron phosphate melt tends to decrease with time. The electrical resistivity of iron phosphate melts containing simulated HLW is similar to that of iron phosphate melt with corresponding soda content. The redox ratio increase greatly with melting temperature and slightly increases with holding time. The activation energy of these melts is discussed using the Mott theory. It is found that the melts with low soda content are electronic conductors and the irreversibility is correlated to the redox ratio.