TEM characterization of dislocation loops in proton irradiated single crystal ThO2

Abstract

• This paper reports the full characterization of dislocation loops in single crystal ThO 2 after 0.47 dpa proton irradiation at 600 o C. • Dislocation loops were found to be mainly edge type with different variants of faulted 1 / 3 〈 111 〉 Frank loops along { 111 } habit plane. • Inside-outside contrast technique and atomic resolution STEM-HAADF imaging revealed the interstitial nature of dislocation loops. This work focuses on the full characterization of dislocation loops induced by proton irradiation in single-crystal ThO 2 . Irradiation was performed using 2 MeV H + ions with sample temperature at 600 o C and a dose of up to 0.47 displacements per atom (dpa). Transmission electron microscopy (TEM) characterization was performed on a large number of dislocation loops. Burgers vector ( b → ) analysis using standard g → . b → = 0 invisibility criterion revealed different variants of 1 / 3 〈 111 〉 type dislocation loops. TEM analysis of edge-on dislocation loops was used to determine habit planes as { 111 } type. The nature of dislocation loops was revealed using the inside-outside contrast method as interstitial type. Rel-rod dark field images were obtained by selecting streak at g → = 1 / 2 [ 31 1 ¯ ] in diffraction pattern to identify the Frank loops present in the microstructure. Subsequent analysis of a single dislocation loop using atomic resolution scanning transmission electron microscopy (STEM) confirmed the interstitial nature of the loop with { 111 } habit plane.