RADIATION-DAMAGE IN LITHIUM ORTHOSILICATE

Radiation damage in lithium orthosilicate (Li4SiO4) and Al-doped Li4SiO4 (Li3.7Al0.1SiO4) irradiated with oxygen ions was studied with ionic conductivity measurements, Raman spectroscopy, Fourier transform infrared photo-acoustic spectroscopy (FT-IR PAS) and transmission electron microscopy. It was seen from the ionic conductivity measurements that lithium-ion vacancies were introduced as irradiation defects for Li-ions sites in both materials due to the irradiation. By the Raman spectroscopy, oxygen atoms in SiO4 tetrahedra were considered to be preferentially displaced due to the irradiation for Li4SiO4, although only a decrease of the number of SiO4 tetrahedra occurred for Li3.7Al0.1SiO4 by displacement of both silicon and oxygen atoms. Decomposition of SiO4 tetrahedra and formation of some new phases having Si-O-Si and Si-O bonds were found to take place for both Li4SiO4 and Li3.7Al0.1SiO4 by FT-IR PAS. In the electron microscopy, damage microstructure consisting of many voids or cavities and amorphization were observed for Li4SiO4 irradiated with oxygen ions. The recovery behavior of radiation damage mentioned above was also investigated.