K. Somaiah

Growth and glow curves of KMgF3:Gd

Abstract Single crystals of KMgF3 are grown by the slow cooling technique. The Thermally Stimulated Luminescence (TSL) of KMgF3 showed three glow peaks at 350, 490, 580K. Incorporation of trivalent gadolinium caused an additional glow peak at 430K suppressing the 350K peak. The low temperature TSL of KMgF3, showed glow peaks at 103, 137, 157, 185 and 275K. The presence of gadolinium caused a shift towards a higher temperature in respect of all low temperature glow peaks. The glow peaks have been explained in terms of F, F2, and Vk- centers.

Thermoluminescence and defects of Sr1−xEuxF2+x solid electrolytes

Abstract Thermoluminescence (TL) studies of the Sr 1 − x Eu x F 2 + x mixed system have revealed three groups of TL glow peaks in the temperature ranges (340, 360–370 K), (460–475, 540–575 K) and (615–635, 680–720 K). The TL emission spctrum of SrF 2 consists of two emission bands at 475 and 700 nm, whereas in Sr 1 − x Eu x F 2 + x additional TL emission bands are obtained at 418, 500, 580 and 745 nm. Electron-beam-irradiated Sr 1 − x Eu x F 2 + x showed optical absorption bands at 265, 464 and 500 nm ( x = 0), while in other compositions these are suppressed, resulting in additional bands at 226, 328, 345, 355, 365 and 385 nm. The intensity of the 370 K glow peak increases with increasing europium concentration. Room-temperature annealing also caused an increase in the intensity of the 370 K glow peak. Upon comparison of TL, TL emission, optical absorption and room-temperature annealing studies, the 370, 460 and 550 K glow peaks were attributed to radiative impurity luminescent centers and radiative recombination of electrons with holes being deexcited from two stages of F-centers. The corresponding TL emissions are at 475 and 700 nm. The TL emission bands of Sr 1 − x Eu x F 2 + x at 418 nm and at 500, 550, 580 and 745 nm are the characteristic emissions of Eu 2+ and Eu 3+ , respectively, and a tentative energy-level diagram is proposed.

X-ray excited and thermoluminescence of gadolinium activated KCaF3

X-ray excited luminescence of KCaF3:Gd is studied in the temperature range of 300K down to 10K. The luminescence spectra shows two emission bands at 360 and 446 nm, in addition to gadolinium characteristic emission lines around 313 nm. As the temperature is lowered to 10K, the 446 nm emission is increased while the 360 nm band gets quenched. The two emission bands at 360 and 446 nm have been ascribed to native impurities and radiative recombination of electrons with Vk- centers respectively. The thermoluminescence of X-irradiated KCaF3:Gd showed three glow peaks around 365, 400 and 540K, the origin of these glow peaks has been discussed and attributed to impurities, F and F-aggregate centres, respectively.

X-ray excited luminescence of Sr1-xEuxF2+x solid solutions

X-ray excited luminescence of SrF2 revealed a sharp and a broad emission band at 231.5 and 316.5 nm respectively while the presence of small concentrations of Eu+3 in SrF2 showed emission bands at 301 and 417 nm. Increase in europium concentration resulted in sharp bands towards red region around 593, 617, 693 and 702 nm and suppressed the broad bands at 301 and 417 nm. The emission bands at 231.5, 316.5 nm in SrF2 and 275, 301 nm in Sr1-XEuXF2+X are attributed to host emission and ionization of VK centers due to fluorine ions while the others are characteristic emission bands of europium. An energy transfer from the host as well as VK centers emission may be responsible for exciting europium and resulting sharp emissions towards red region.

Glow curves and F-aggregate centers in RbMgF3

It has been identified that V K , F, F 2 (M) and F 3 (R) centers could be created under appropriate conditions. The purpose of the present investigation is to describe the nature of these defect centers by thermoluminescence studies, which have not been reported hitherto to the knowledge of the authors. The preliminary results of the thermoluminescence glow curves are being reported with possible explanation

Thermoluminescence of SrFCl crystals

The thermoluminescence and optical absorption spectra of X-irradiated SrFCl crystals is studied. Three glow peaks are observed around 342K, 375K and 438K, and these are resolved by a thermal cleaning technique. The peaks are analysed using first-order kinetics; the trap depth and frequency factor values obtained agreeing quite well with values calculated using various other methods.