Volumenänderung von Alkalihalogenidkristallen bei der Bildung von Gitterdefekten durch niederenergetische Strahlung

Abstract

Defects were created in the alkali halides KBr and KCl by X-irradiation. The type of disorder was determined by combined lattice parameter and length change measurements. The change of the lattice parameter was determined by the shift of a Bragg reflex, and the length change was detected by an inductive transducer. To omit thermal annealing and conversion of defects the crystals were irradiated below 10 °K. Defects are created as Frenkel defects. They anneal in distinct annealing stages, and this Frenkel disorder remains unchanged during annealing. Volume change and lattice distortion due to different defects are obtained by combined absorption and length change measurements. In KBr the volume change of two different Frenkel pairs was detected. A pair consisting ofα- andI-center causes the volume change (Δ)_{α +I} =3.2 atomic volumes and a pair ofF- andH-center(Δv) _F+H =1.2 atomic volumes.