Ion beam modification of Tl-Ba-Ca-Cu-O type high temperature superconductors during irradiation

Microstructural modification of high temperature superconductor (HTS) single-crystal plates of Tl-1212 and Tl-2212 (numbers designate the Tl/Ba/Ca/Cu cation ratio) was studied during 1.5 MeV Kr{sup +} and Xe{sup +} ion irradiation with in-situ electron diffraction and after ion irradiation with high resolution TEM (HRTEM). Similar in-situ temperature dependence effects are seen for both phases. During irradiations from 22K to 673K, an amorphous halo develops after very low ion dose or fluence (1.7 {times} 10{sup 12} ions/cm{sup 2}). During irradiation at 100 and 300K, complete amorphization is obtained, while at 22 and {ge}533K, the halo fades slightly and a polycrystalline ring pattern develops, indicating ion irradiation induced crystallization occurred. After a low ion dose (8.5 {times} 10{sup 12} ions/cm{sup 2}) at 100 and 300K, HRTEM reveals amorphous regions 5-20 nm in size which are not columnar and do not all penetrate the entire sample thickness. At 22 and {ge}533K, Moire fringes and misoriented crystallites of cascade size are observed. The 4-6nm crystallites are thallium-rich