Influence of X-ray irradiation time on deformation luminescence of KCl:Eu ²⁺ single crystals after compressive deformation

KCl Single crystals doped with Eu2+ (0.03 mol% in melt) were compressively deformed at the cross-head speed of 50 µm min-1 until the dynamic recovery region of strain hardening. The crystals were irradiated with X-ray for various exposure times at room temperature. The optical absorption (OA) and the thermoluminescence (TL) glow were measured for the crystals. The absorption peak at the wavelength near 560 nm in the OA spectrum becomes larger rapidly with the increment of irradiation time until 30 min and then is saturated above approximately 50 min. The small absorption peak near 820 nm due to the M-centre tends to increase dependently on the X-ray irradiation time for times below 150 min. As for the TL glow curve, two peaks appear at about 370 and 450 K. Both the peak intensities grow until the irradiation time of 30 min and seem to be later saturated above 50 min. A peak also appears around 330 K on the TL glow curve for the crystals, but this peak is not observed in the case of irradiation alone for the same time without deformation. The peak intensity increases with the X-ray irradiation time up to 30 min. This is considered to be the reason why the number of F-centres lying in the expansion region of the dislocation segments increases with the irradiation of the KCl:Eu2+ crystals using X-ray. Thereafter, the intensity decreases slightly with increasing the irradiation time.