Growth and instability of charged dislocation loops under irradiation in ceramic materials

We have investigated the physical mechanisms of the growth and stability of charged dislocation loops in ceramic materials with very strong different mass of atoms (stabilized cubic zirconia) under different energies and types of irradiation conditions: 100-1000 keV electrons, 100 keV He⁺ and 300 keV O⁺ ions. The anomalous formation of extended defect clusters (charged dislocation loops) has been observed by TEM under electron irradiation subsequent to ion irradiation. It is demonstrated that very strong strain field (contrast) near charged dislocation loops is formed. The dislocation loops grow up to a critical size and after then become unstable. The instability of the charged dislocation loop leads to the multiplication of dislocation loops and the formation of dislocation network near the charged dislocation loops. A theoretical model is suggested for the explanation of the growth and stability of the charged dislocation loop, taking the charge state of point defects. The calculated distribution of the modified strain field by the electrical field around the charged dislocation loops is stronger than that of noncharged dislocation loops. The obtained theoretical results for the modified strain field contrast and the critical radius of unstable charged dislocation loops are compared with observed experimental data.