[en] In order to have a better idea of the interaction of the defect centres produced by gamma-irradiation with dislocation in the processes of deformation destruction, mechanoluminescence (ML) and thermoluminescence (TL) of gamma-irradiated CaSO₄:Dy, these phoshors have been investigated. CaSO₄:Dy phosphors were prepared by dissolving CaSO₄.2H₂O in sulphuric acid and evaporating the excess acid around 300 deg. C. ML was excited impulsively by dropping a load on to the sample. Two peaks have been observed in the ML intensity against time curve. The total light output, i.e. integrated ML intensity, increases with concentration of dopant, strain rate and with irradiation doses. The TL glow curves of CaSO₄:Dy phosphors at different concentrations of dopant and irradiation doses were also recorded. Studies of the influence of post-irradiation annealing on the ML of CaSO₄:Dy show that with the removal of the TL dosimetric peak (∼210 deg. C) the ML intensity decreases markedly. A spectroscopic study of ML and TL has also been carried out to elucidate the mechanism of ML. Correlation between ML and TL has also been found. (author)

[en] Published in summary form only

[en] Interaction of moving dislocation with defect centres in γ-irradiated Ba, Sr, Ca and Pb doped NaCl and LiF single crystals has been studied. It has been found that the mechanoluminescence (ML) intensity increases significantly with the impurity doping in the crystals. When the mobile dislocations interact with F-centres, they release electrons which recombine with the luminescence centres and in turn, give rise to the emission of radiation. The higher difference between the ionic sizes of impurity and host ions may produce higher concentration of vacancies in the crystals. This may cause higher production of F-centres in the crystals and consequently the ML intensity may be enhanced. (author). 2 refs., 3 figs., 4 tabs

[en] The effect of Sm concentration, g- irradiation and temperature on the Mechanoluminescence (ML) of CaSO₄ : Sm phosphors have been studied. Two peaks are observed in the kinetics of ML. The optimum ML efficiency has been observed for CaSO₄ : Sm (0.2wt%) phosphors at 75 degC, however, saturating in ML intensity was observed at g -dose of 3 x 10³ Gy. On the basis of experimental results, a suitable mechanism for ML excitation has been discussed and it is speculated that the prominent emission at 485 nm is may be due to ⁴F_5/2-⁶H_7/2 transition. (author)

[en] The present paper reports the effect of various parameters such as particle size, radiation dose, temperature of the solvent on Lyoluminescence (LL) of gamma-irradiated Sodium Bromide samples. LL emission spectrum has also been recorded for better understanding of LL excitation. The Sodium Bromide crystals were grown by melt technique and irradiated for different times using ⁶⁰Co source. The light-emission during dissolution of irradiated water was detected. An optimum value has been observed in the LL intensity versus time curve. It has been found that the total light output i.e. LL intensity, increases with particle size; temperature of the solvent and wavelengths of light, attains an optimum value and then decreases, whereas in the case of increasing radiation dose, peak LL intensity Im5 attains a saturation value. The optimum values of LL intensity obtained are 120μm. 70 deg C and 480 nm respectively in the case of dependence of particle size, temperature of the solvent and emission spectrum. (author)

[en] The effect of temperature on the DL intensity of g- irradiated RE doped CaF₂ crystals has been investigated. The DL was excited by successive application and release of a load on to the crystal. The DL intensity during application as well as release of pressure increases with temperature, attains optimum value then decreases with further increase in temperature. The probable factors responsible for change in DL intensity with temperature have been discussed in this paper. (author)

[en] In the frame of nationwide survey project, measurement of indoor radon/thoron level has been carried out in 132 dwellings situated in 10 different towns/villages of centrally located states Madhya Pradesh and Chhattisgarh. LR 115 solid-state nuclear track detectors in plastic twin chamber dosimeter cups were used for the measurement. The measurements were carried out for a full year, divided into four quarters. The mean radon/thoron concentration at all the locations falls well below the range of active level recommended by International Commission on Radiological Protection. The results of uranium, thorium and potassium estimation in soil samples belonging to these areas are also reported. Positive correlation has not been observed between indoor radon/thoron concentration and uranium/thorium content of the soil. It is concluded that the diffusion of radon from soil to dwelling is greatly affected by flooring material

[en] Nanocrystalline YAG doped with Eu"3"+ and Nd"3"+ has been synthesized by a sol–gel technique. The prepared nanophosphors were calcined and characterized by XRD, SEM. The XRD analysis revealed well-defined cubic phase. Electron microscopy showed spherical morphologies with an average size of 15–20 nm. The thermoluminescence (TL) properties of as prepared nanophosphors were investigated after γ-irradiation using "6"0Co source at room temperature. It has been found that there is a prominent TL glow peak at 290–295 °C for the as prepared doped samples. The TL glow curve showed variation in TL peak intensity as the concentration of dopant is changed. Kinetic data and trap depth for the synthesized samples were calculated by a peak shape method. It has been found that TL response is nonlinear in the range 0.29–1.16 kGy. This paper discusses about the optimal doping concentration of Eu and Nd in YAG nanophosphors. - Highlights: • TL properties of YAG:Eu"3"+/Nd"3"+ nanoparticles were investigated after γ-irradiation. • TL peak intensity and glow curve structure varies with concentration of dopant. • Optimal TL intensity was obtained for YAG:Eu_3_._0. and YAG:Nd_3_._0. • Blue-shift in the TL peaks was observed as the gamma dose is increased for YAG:Eu_5_._0. • TL response was found to be nonlinear in the range 0.29–1.16 kGy

[en] In order to find the mechanical stability of traps/luminescence centers responsible for TL in MgSO₄:Dy system, effect of deformation on TL of MgSO₄:Dy was studied. TL glow curve of MgSO₄:Dy phosphor is complex and peaks around 110, 150 and 220 °C were observed. Optimum TL was obtained for the sample having 0.1 mol% concentration of Dy in MgSO₄ system. Slight increase in intensity of 110 °C peak was observed when the TL glow curve was recorded after deforming the irradiated samples by dropping a piston of mass 0.4 kg onto it from the height of 0.2 m. Further increasing the height from which the piston was being dropped TL peak intensity of 110 °C decreased. However, 150 °C and 220 °C TL peak intensity decreased with deformation. Result showed that trap centers associated with 150 °C and nearby TL peaks were most mechanically unstable. TL spectrum of MgSO₄:Dy phosphors was also recorded. Two peaks one at 490 nm and another at 590 nm were observed. In the TL emission spectra recorded for deformed samples, no significant change was seen in the peak positions. However, peak intensity was reduced. It is suggested that the recombination of electrons released from the traps during the thermal excitation is responsible for the TL emission in this system. It seems that in MgSO₄:Dy system deformation does not cause any appreciable change in the recombination mechanism, it causes redistribution of traps and therefore change in relative TL intensity occurs in the same spectral region.

[en] Photoluminescence (PL), thermoluminescence (TL) and mechanoluminescence (ML) of rare-earths (RE) doped BaSO₄ and MgSO₄ phosphors were studied. Undoped and doped phosphors containing different concentrations of dopant were synthesized by solid-state reaction method. X-ray diffraction (XRD) pattern of the samples matched well with their standard data of Joint Committee on Powder Diffraction’s (JCPD) file. In the PL spectrum of Dy doped samples, peaks around 470 and 580 nm were observed due to transition of Dy³⁺ ion. Eu doped BaSO₄ showed PL peak at 380 nm due to transition of Eu²⁺ ion, however, in the PL spectrum of MgSO₄:Eu phosphors, transition of Eu³⁺ was also observed along with transition of Eu²⁺ ion. Dy doped γ-ray-irradiated BaSO₄ and MgSO₄ phosphors showed at least two distinct peaks in their TL glow curves. The first peak occurred in range 120–150 °C and the second peak was observed in the range 220–230 °C. The TL glow curve of γ-ray-irradiated BaSO₄:Eu contained a distinct peak at 170 °C. Two distinct peaks, one at 110 °C and another at 220 °C were observed in the TL glow curve of γ-ray-irradiated MgSO₄:Eu phosphors. TL spectra showed that RE ions act as luminescence centre in BaSO₄ and MgSO₄ system. When the ML was excited impulsively by dropping a load on to the γ-ray-irradiated samples, only one sharp peak was observed in the ML intensity versus time curve of Dy doped samples, however, two peaks were observed in the ML intensity versus time curve of Eu doped BaSO₄ and MgSO₄ phosphors. The ML spectra of samples showed the characteristic emission of rare-earth impurities. Experimental results suggest that although almost similar states are responsible for PL, TL and ML, the luminescence efficiency of the phosphors depends on the mode of excitation.