DAMAGE OF YBA2CU3OX BY ION IRRADIATION

Specimens of high-Tc superconductor YBa2Cu3Ox have been irradiated with Si ions (7 MeV) up to 10 ions/nm2. Monolayers of fine particles (less than 5 ω size) were prepared on metal plates and X-ray diffraction patterns were taken before and after the irradiations. Intensities of all diffraction peaks decrease continuously with increase in fluence with a damage cross section of 0.21 nm2 without observation of a critical or threshold fluence. A 50% loss in crystallinity is observed at ∼ 3.6 eV/atom (0.12 dpa) although the rate of amorphization may increase beyond a fluence of ∼ 4 ions/nm2. Bragg diffraction peaks have disappeared and amorphization is complete by ≈10 eV/atom (0.33 dpa). Peak positions shift toward lower 2θ values indicating lattice expansion contributed to by point defects. There is a gradual transformation from orthorhombic toward tetragonal structure with the b0 parameter changing very little. c0 increasing by ≈ 0.6%, and α0 also increasing by ≈ 1% to approach b0. The damage cross section of the tetragonal phase is larger than that of the orthorhombic phase. © 1990.