PAT applications to defect formation in solids

5 PAT applications to defect formation in solids In metals, most semi-conductors and ionic solids, no Ps is formed the useful probe is thus e+. Being charged, this probe is sensitive to negatively charged defects, such as cation vacancies, in which it can be trapped. In most chemical applications, and particularly in molecular solids, the useful probe is Ps the trap is then expected to be neutral (e.g. molecular vacancy). 

The trapping rate constant obeys the Arrhenius equation, as  

In crushed crystals, t varies in a completely different way during the first heating run and in a similar way as in the untreated material in subsequent heating and cooling cycles the extrinsic defects created upon crushing are thus shown to be annealed out at about 403 K. 

The occurrence of well defined sigmoidal variations of the e+ or o-Ps lifetimes with T may fail to be observed. This is the case in Agl, a compound well known to present a transition to an ionic superconducting phase above 423 K, due to the production of large amounts of cation vacancies. However, none of the PALS or DB parameters show evidence of a change at the phase transition temperatures [130], As it seems, the lifetime of the cation vacancy is too short to allow e+ trapping, due to the intense movement of the Ag+ ions from vacancy to vacancy through the lattice. 

Extending PAT applications to the study of solid state chemistry, defect formation and annealing, nature of defects, ionic conductivity, etc, is a challenging field yet almost unexplored. 

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