Development of Neutron Radiography Technique to Visuslize Lithium Ions in Solod Electrolytes

(1)在京都大学反应堆NR装置中安装了红外束电加热器，用于高温下固体电解质中Li^+运动的原位测量。利用一些模拟样品（湿陶瓷材料）对加热器的性能及其对设备的影响进行了实验评估。(2)利用中子射线照相技术研究了锂离子在高温型离子导体Li_<1.33>Ti_<1.67>O_4中的转移。通过特殊制备的不同同位素比（^6Li/^7Li）氧化物，通过直流电流进行电解，得到一组NR图像，证实了锂离子在氧化物中的导电。对图像的分析表明，氧化物的锂离子输运数几乎等于1.0,Li_<1.33>Ti_<1.67>O_4中的锂离子根据电场的极性几乎可逆地转移。(3)采用冷中子射线照相技术研究了Ca_<0.95>Li_<0.10>WO_4取代白钨矿型氧化物中锂离子的导电行为。用不同^6Li/^7Li比值的电解氧化物的一组中子射线照相图像获得了锂离子的分布曲线。他们发现氧化物的锂离子输运数为0.99，这与电化学测量的结果一致。此外，他们指出Ca_<0.95>Li_<0.10>WO_4中只有一半的锂离子可以随电荷转移而移动，而另一半则停留在钙离子位置。因此，可以认为锂离子的导电性是由于间隙中有50%的锂离子。(4)证实了冷中子射线照相与成像板相结合可以有效地提高氧化物中Li^+的测量精度。

(1) An electric heater using IR beam was installed in the NR facility of Kyoto University Reactor for in-situ measurements of Li^+ movement in solid electrolytes under high temperature. The performance of the heater and its influence to the facility were experimentally evaluated using some simulated samples(ceramic materials wet with water).(2) Neutron radiography was used to study the transfer of lithium ions in the high temperature-type ionic conductor, Li_<1.33>Ti_<1.67>O_4. After dc current was passed for electrolysis through specially prepared xides with different isotope ratios(^6Li/^7Li), a set of NR images was obtained, which confirmed the lithium ion conduction in the oxides. Analysis of the imagesclarified that the lithium ion transport number of the oxide is almost equal to 1.0 and that lithium ions in the Li_<1.33>Ti_<1.67>O_4 were transferred almost reversibly according to the polarity of the electric field applied.(3) Cold neutron radiography was applied to study the lithium ion conduction in the substituted scheelite-type oxide of Ca_<0.95>Li_<0.10>WO_4. The lithium ion distribution profile were obtained from a set of neutron radiography images of the electrolyzed oxides having different ^6Li/^7Li ratios. They showed that the lithium ion transport number of the oxide is 0.99, which coincided with the result of electrochemical measurements. Furthermore, they denoted that only a half of all lithium ions in Ca_<0.95>Li_<0.10>WO_4 can move with charge transfer, but another half stays at the calcium sites. Therefore, it can be considered that the lithium ion conduction would be due to the 50% of the interstitial lithium ions.(4) It was confirmed that the combination of cold neutron radiography and an imaging plate was effective to improve the accuracy of the technique to measure Li^+ in the oxides.