Photoplastic Effects in Colored KBr Single Crystals Containing Potassium Metal Colloids (II)

In order to clarify the mechanism of the photoplastic effect (PPE) in densely colored potassium bromide single crystals the control as well as the identification of the relevant defects as to PPE are substantial problems. The electrolytic coloration of the KBr speci-mens of size 10 X 10 X 15mm3 has been carried out in the electric furnace held at 540t for few hours. Thus obtained colored KBr specimens containing the higher concentration of the F-centers were subjected to the isothermal annealing at 100t for long period of time up to 400 hours. The observation of the PPE in terms of both potassium metal colloids and F-centers has been done in detail through the optical absorption measurements. It was found that the most effective change of the F-centers into the potassium metal colloids has occurred in the course of the isothermal annealing at 100t for 300h. The PPE observations have been performed by using the specimens after optimum isothermal annealing treat-ment. A brief discussion is devoted to the characteristic profiles of the PPE due to the potassium metal colloid particles as well as the F-centers in KBr specimens. Key Words : photoplastic effect, colored KBr single crystal, electrolytic coloration, potassium metal colloid, isothermal annealin