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short communications
The influence of thermal treatments on the dislocation density in a lithium fluoride single-crystal has been studied using Lang's X-ray diffraction topography technique. Three principal types of dislocation arrangement, polygonization walls, high (104 cm cm-3) and low (≲ 102 cm cm-3) dislocation-density subgrains were observed. It is found that obtaining specimens suitable for X-ray observation requires severe thermal preparation conditions and depends particularly on the cooling rate (10°C/h).