基于辐射-离子效应的掺钆氧化铈晶界阻抗热中子响应预测

中文摘要 AI 辅助

辐射-离子效应已在3 mol% Gd掺杂的CeO2（3GDC）中被报道：在35 Gy/min的60Co伽马辐照下，室温时块体颗粒的晶界（GB）离子电阻降低了680倍，因为辐射产生的电子被晶界核心捕获，降低了空间电荷势。该效应仅在光子条件下得到验证。本文预测了3GDC对热中子的响应。中子被157Gd（254 kb）吸收；每次俘获约50 keV的能量通过转换电子和俄歇电子在1微米内沉积，且Gd偏析于晶界，因此能量被输送到阻碍离子传输的界面。该源项被表示为晶界有效产生速率，并用于基于已发表的伽马数据校准的Mott-Schottky/Seager框架中。伽马温度序列确定了单一陷阱参数（约1.1 eV）的温度依赖性，该校准重现了从独立薄膜紫外数据在400°C时获得的陷阱参数。6×10^9 cm^-2 s^-1的热中子通量给出的晶界有效产生速率与35 Gy/min校准相同。在室温下，预测的晶界电阻比在10^9通量下约为150（90%置信区间100-290），在10^10通量下约为1300（900-2500）；在10^9通量下，响应在60°C以上消失，在10^10通量下，响应在80°C以上消失。由于俘获事件是离散的，连续源描述仅在单次事件的俘获电荷持续到下一次事件时才成立；这在10^10通量下满足，在10^9通量下勉强满足，因此恢复时间常数是中子实验应测量的第一个量。自屏蔽部分被俘获光子的康普顿吸收所抵消；当Gd含量超过5 mol%时，响应受到弱暗势垒的限制。本文给出了验证预测所需的源参数、样品几何形状和控制条件。

英文摘要

The radiation-ionic effect was reported in 3 mol% Gd-doped CeO$_2$ (3GDC): under $^{60}$Co gamma irradiation at 35 Gy/min, the grain-boundary (GB) ionic resistance of a bulk pellet decreased 680-fold at room temperature because radiation-generated electrons trapped at the GB core lower the space-charge potential. The effect has only been demonstrated with photons. Here the response of 3GDC to thermal neutrons is predicted. Neutrons are absorbed by $^{157}$Gd (254 kb); about 50 keV per capture is deposited within 1 $μ$m by conversion and Auger electrons, and Gd segregates to the GBs, so the energy is delivered to the interfaces that block ionic transport. This source term is expressed as a GB-effective generation rate and used in the Mott-Schottky/Seager framework calibrated on the published gamma data. The gamma temperature series fixes the temperature dependence of the single trap parameter (about 1.1 eV), and this calibration reproduces the trap parameter obtained from independent thin-film UV data at 400 $^\circ$C. A thermal flux of $6\times10^{9}$ cm$^{-2}$s$^{-1}$ gives the same GB-effective generation rate as the 35 Gy/min calibration. At room temperature the predicted GB resistance ratio is about 150 (90% interval 100-290) at $10^{9}$ and about 1300 (900-2500) at $10^{10}$ cm$^{-2}$s$^{-1}$; the response vanishes above 60 $^\circ$C at $10^{9}$ and 80 $^\circ$C at $10^{10}$. Because capture events are discrete, the continuous-source description holds only if the trapped charge of one event outlasts the next; this is met at $10^{10}$ and marginal at $10^{9}$, so the recovery time constant is the first quantity a neutron experiment should measure. Self-shielding is partly offset by Compton absorption of the capture photons; above 5 mol% Gd the response is limited by the weak dark barrier. Source parameters, sample geometry and controls needed to test the prediction are given.

发表机构

• Lancaster University（兰卡斯特大学）

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