Ne²⁺ Ion Irradiation Induced Swelling Effects in Pyrochlore Ho₂Ti₂O₇ by Using a GIXRD Technique

We carry out 400 keV Ne²⁺ ion irradiation damage experiments at cryogenic temperature (about 77 K) on polycrystalline Ho₂Ti₂O₇ pyrochlore. The irradiation fluences range from 2×10¹⁴ to 1.3×10¹⁵ ions/cm², corresponding to the peak ballistic displacement damage of 0.075–0.487 in units of displacement per atom (dpa). The value indicates the statistical average of the fractional number of lattice atoms which have experienced a lattice displacement. Irradiation−induced structural evolution is examined by using grazing incidence x-ray diffraction (GIXRD) at x-ray angles γ=0.25° and 3°. It is found that the irradiated layer is volumetrically swelled as compared with the underlying non-irradiated substrate and the volume increase in the irradiated layer is contributed mainly to the irradiated ion fluence.