Anisotropic Structural Response of NdGaO₃ Single Crystals to 147 MeV Kr-Ion Irradiation

NdGaO₃ is an orthorhombic perovskite substrate whose response to swift heavy ions remains insufficiently understood. Here, (001)- and (110)-oriented single-crystal wafers were irradiated with 147 MeV ⁸⁴Kr¹⁵⁺ ions to 1 × 10¹³ ions/cm² and examined by symmetric Cu Kα X-ray diffraction. Peak shifts were evaluated using a two-parameter strain/sample-displacement model; PDXL was used for phase identification and diagnostic whole-pattern fitting, while SRIM and NIST attenuation data were used to compare the ion range with the absorption-weighted X-ray depth. Irradiation strongly reduced and broadened the principal reflections and enhanced diffuse scattering near 2θ ≈ 30°. Corrected normal strains were 0.30% for (001) and 1.20% for (110). Reflection-specific apparent microstrains were 0.29-0.61% and 0.69-1.31%, respectively. A broad component already present in the Pristine (110) profile increased in fitted area by approximately 63% after irradiation. Full orthorhombic-cell and Williamson-Hall outputs from unconstrained powder-profile fitting are mathematically underdetermined for these highly oriented wafers and were not used quantitatively. Attenuation calculations establish strong overlap between the probed depth and the SRIM-defined modified region, although depth gradients in crystallinity prevent unique assignment of residual Bragg intensity. The results demonstrate pronounced anisotropic disorder without additional crystalline phases.