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Polycrystalline samples of strontium tetraborate (SrB4O7: SBO) samples doped with different concentrations of europium (0%, 0.05%, 1% and 2%) were synthesized using solid state reaction in air at high temperature. These samples were characterized by X-ray diffraction (XRD), photoluminescence (PL), thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) techniques. X-ray diffraction studies indicated that SrB4O7 has orthorhombic structure with lattice parameters a=4.237±0.001, b=4.431±0.001, c=10.704±0.010, space group Pnm2i, Z=2. Thermally Stimulated Luminescence (TSL) investigations on the gamma irradiated sample showed an intense glow peak at 407 K and a weak glow peak at 500 K. The trap parameters namely activation energy (E), order of kinetics (b) and the frequency factor (s) for the main peak at 407 K were determined using the glow curve method. Fluorescence studies showed weak emission at ca 367 nm, which was attributed to f-d transition (4f65d-4f7) of Eu2+ ions in the host lattice, whereas an intense emission in the range 570–650 nm was assigned to 5D0→7FJ, J=0,1,2,3 and 4 transition of Eu3+ in the host lattice. The large value of I(R)/I(O) suggested that Eu3+ ions are situated at sites without center of inversion (lower symmetry) in SBO matrix. EPR studies suggested the formation of boron–oxygen hole trapped center viz, BOHC, electron trapped at oxygen vacancies and some impurity radicals like NO32− and CO2− radicals in SBO on irradiation. EPR temperature variation studies in the range 300–475 K on gamma irradiated europium doped samples, suggested a recombination process occurring between boronoxygen hole trapped species and electron trapped species and subsequently energy is transferred to Eu3+ ion, which on de-excitation yields thermally stimulated luminescence yielding an intense TSL glow peak at 407 K.

The luminescence of uranium in strontium borate (SrB4O7, SBO) matrix was investigated by time resolved photoluminescence, thermoluminescence (TSL) and electron spin resonance techniques (ESR). The samples were synthesized using solid state fusion reaction route and characterized by X-ray diffraction. Photoluminescence excitation and emission data suggested the stabilization of uranium as uranate ( UO 6 6 - ) in the matrix. Luminescence decay time data suggested the stabilization of uranium at two different sites in the matrix. By giving suitable delay times and choosing proper gate widths, the two emission spectra due to the two uranate species could be obtained. Thermoluminescence investigation on the gamma-rays irradiated sample showed a strong glow peak at ∼415 K and a weak glow peak at 505 K. The dose response behavior, the trap parameters along with the order of kinetics for the strong glow peak were determined. To pinpoint the exact chemical nature of the defect centers responsible for the observed glow peaks, electron spin resonance technique was employed. Based on the ESR-TSL correlation data and the observed photoluminescence results, a plausible mechanism for the origin of the luminescence in the system was proposed.

U6+ doped BaSO4 samples were synthesized by precipitation route. PL, TL and EPR investigations of γ and self α irradiated samples were carried out. PL spectra of these samples give structured broad band peaking around 518 nm with five vibronic bands centred around 498·4, 516·0, 533·7, 554·0 and 575·1 nm, respectively and the average frequency of symmetric stretching of O=U=O in the ground electronic state was found to be 674 cm−1. Trap level spectroscopic studies of U doped BaSO4 give glow peaks at 411, 488 and 512 K, respectively and their spectral characteristics are typical of UO $_{2}^{2+}$ emission. EPR studies of γ-irradiated U6+:BaSO4 sample have shown the presence of sulphoxy centred radicals like SO $_{4}^{-}$ and SO $_{3}^{-}$ in addition to OH•, O $_{3}^{-}$ and SH2−. TSL peaks at 411 and 488 K were correlated with thermal destruction of SO $_{4}^{-}$ and SO $_{3}^{-}$ radicals.

Synthesis, X-ray diffraction and photoluminescence investigations of Eu3+-doped SrBPO5 phosphor has been carried out in order to characterize the material. PL emission spectrum of air heated SrBPO5:Eu3+ phosphor exhibits bands at 590, 614, 651 and 702 nm under 238 nm excitation, assigned to the 5D0→7FJ (J=1, 2, 3, 4) transitions of Eu3+ ions. Of these transitions, the emission centered at 614 nm is the most prominent. Photoluminescence decay time and Time-resolved emission spectrometric (TRES) studies of Eu3+ were carried out with λem=614 nm and λex=238 nm. It suggested that Eu3+ ions are present at two different sites and predominantly occupying Sr2+ sites in the host lattice. Judd–Ofelt intensity parameters and other radiative properties were evaluated from the emission spectrum by adopting standard procedure. The trend observed in the J–O parameters (Ω2>Ω4) confirms the covalency exiting between the Eu3+ ion and ligands as well as the asymmetry around the metal ion site. The color coordinates of the system were evaluated (x=0.558 and y=0.355) and plotted on a standard CIE index diagram. The observations showed that the SrBPO5:Eu3+ phosphor is very close to the red emission material. Photoluminescence intensity was compared with that of a commercial red phosphor for commercial utility purpose. It is observed that, the photoluminescence intensity of the prepared phosphor was 60% as compared to the commercial phosphor Y2O3: Eu.

Eu3+-doped ZnAl2O4 phosphors were successfully synthesized in air atmosphere at 900 °C. The phosphors were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermally stimulated luminescence (TSL) and photoluminescence (PL) techniques. The average particle size of the system as determined from SEM was found to be 100–150 nm (for samples annealed at 900 °C). PL spectra of the doped phosphors showed emission peaks corresponding to Eu3+ ions. Lifetime studies revealed Eu3+ ions to be in two different sites. The asymmetric ratio (I616/I592) was observed to be about 3.75. This suggested that Eu3+ ion entered the host mainly substituting Al3+ site distorting the local environment and is partly located on surface of the phosphors. A prominent glow peak at 430 K was observed in the TSL of γ-irradiated Eu3+-doped ZnAl2O4 phosphors. Trap parameters for this peak have been determined and the probable mechanism for the glow peak is proposed. CIE chromaticity coordinates for the system were evaluated. It was observed that, the system could be employed as a potential red emitting phosphor. Commercial utility of the phosphor was investigated by comparing it with commercial red phosphor. The PL intensity of the as prepared phosphors was 63% of that of the commercial phosphor. Apart from this, various radiative properties such as the Judd–Ofelt intensity parameters, spontaneous emission probabilities, luminescence branching ratios, radiative lifetimes and quantum efficiency were evaluated for the system.

Eu 3+ doped boro-tellurite glasses with the chemical composition (69 − x )B 2 O 3 – x TeO 2 –15Mg 2 O–15K 2 O–1Eu 2 O 3 (where x = 0, 10, 20, 30 and 40 wt%) have been synthesized and its thermal, structural and spectroscopic behavior were studied and reported. The thermal behavior of the Eu 3+ doped boro-tellurite glasses were explored through DTA thermograms. The presence of varying tellurium dioxide results in structural and spectroscopic changes around Eu 3+ ions and are explored through XRD, FTIR, UV–vis, Luminescence and lifetime measurements. The XRD pattern confirms the amorphous nature and the FTIR spectra reveal the formation of the local structural units BO 3 and BO 4 in the prepared glasses. The bonding parameters ( β and δ ) have been calculated based on the observed band positions of the absorption spectra. The Judd–Ofelt (JO) parameters were determined from the absorption and luminescence spectra and the results are presented. The variation in the JO intensity parameters Ω λ ( λ = 2, 4 and 6) and the hypersensitive band positions with the change in chemical composition have been discussed in detail. The JO parameters have been used to derive important radiative properties like transition probabilities ( A ), branching ratios ( β R ) and peak stimulated emission cross section ( σE / P ) for the 5 D 0 → 7 F J ( J = 1, 2, 3 and 4) transitions of the Eu 3+ ions. The varying optical properties of the prepared glasses with the change in tellurium dioxide have been studied and compared with similar results.

Trap level spectroscopic studies were carried out on γ-irradiated Tb (1 mole%) doped SrBPO5 were carried out using photoluminescence (PL), thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) techniques. The incorporation of Tb in the 3+ oxidation state was ascertained from PL studies. Life time for Tb3+ emission corresponding to the intense transition 5D4 → 7F5 at 543 nm was determined. The spectral characteristics of the TSL glows have shown that Tb3+ ions act as the emission center for the glow peak at 475 K. The trap parameters of the glow peak were determined. EPR investigations at room temperature/77 K revealed the stabilization of three boron oxygen hole trapped centers (BOHC's) and oxygen centered radicals such as O− and O2− and trapped electrons in room temperature γ-irradiated samples. TSL glow peak at 475 K was found to be associated with recombination of electron released from trapped electron center and the BOHC2 center.

Lithium titanate ceramics doped with Eu were synthesized and their photoluminescence (PL) and emission spectral characteristics were investigated. PL spectra of the sample showed peaks corresponding to the 5D0→7FJ (J=0, 1, 2, 3 and 4) transitions under 230 nm excitation. The fluorescence lifetimes of Eu3+ ions were found out to be 645 μs. Strong red emission coming from the hypersensitive 5D0→7F2 transition of Eu3+ ion suggested the presence of the dopant ion in highly asymmetric environment. Further analysis of the emission spectrum revealed that the symmetry of the metal ion is very low i.e. C2. The emission intensity of the sample was compared with a commercial phosphor to get an idea about the commercial utility of the phosphor. Various emission properties for the system namely Judd–Ofelt intensity parameters, spontaneous emission probabilities, branching ratios, radiative lifetimes and quantum efficiency were evaluated for the dopant ion by adopting standard procedure.

Adsorptive sorbent for bio-aggressive natural aqueous media like seawater was developed by one pot simultaneous synthesis of silver nanoparticles (Ag nps) and poly(ethylene glycol methacrylate phosphate) (PEGMP) by UV-initiator induced photo-polymerization. The photo-polymerization was carried out by irradiating N,N'-dimethylformamide (DMF) solution containing appropriate amounts of the functional monomer (ethylene glycol methacrylate phosphate), UV initiator (α,α'-dimethoxy-α-phenyl acetophenone), and Ag(+) ions with 365 nm UV light in a multilamps photoreactor. To increase mechanical strength, nano-composite sorbent (Ag@PEGMP) was also reinforced with thermally bonded non-woven poly(propylene) fibrous sheet. Transmission electron microscopy (TEM) of the nano-composite sorbent showed uniform distribution of spherical Ag nanoparticles with particles size ranging from 3 to 6 nm. The maximum amount of Ag(0) that could be anchored in the form of nanoparticles were 5±1 and 10±1 wt.% in self-supported PEGMP and poly(propylene) reinforced PEGMP matrices, respectively. Ag@PEGMP sorbent was found to be stable under ambient conditions for a period of six months. Ag@PEGMP composite sorbent did not exhibit growth at all after incubation with pre-grown Escherichia coli cells, and showed non-adherence of this bacteria to the composite. This indicated that composite sorbent has the bio-resistivity due to bacterial repulsion and bactericidal properties of Ag nanoparticles embedded in the PEGMP. Sorption of U(VI) in PEGMP and Ag@PEGMP nano-composite sorbents from well-stirred seawater was studied to explore the possibility of using it for uranium preconcentration from bio-aggressive aqueous streams. The nano-composite sorbent was used to preconcentrate U(VI) from a process aqueous waste stream.

Lithium titanate ceramics doped with three rare earth (RE) ions namely Eu 3+ , Dy 3+ and Tb 3+ were synthesized and their photoluminescence (PL) properties were investigated. PL spectra of Eu doped sample showed peaks corresponding to the 5 D 0 → 7 F j ( j =0, 1, 2, 3 and 4) transitions under 230 nm excitation. Strong red emission coming from the hypersensitive 5 D 0 → 7 F 2 transition of Eu 3+ ion suggested the presence of the dopant ion in a highly asymmetric environment. Dy doped samples showed the Dy 3+ emission characteristic due to 4 F 9/2 → 6 H 15/2 and 4 F 9/2 → 6 H 13/2 transitions. Their relative intensity ratios also suggested the presence of asymmetric environment around the metal ion. In case of the Tb 3+ doped sample blue-green emission corresponding to the 5 D 4 → 7 F j ( j =6, 5 and 4) transitions was seen. The fluorescence lifetimes of Eu 3+ , Dy 3+ and Tb 3+ ions were found to be 645, 900 and 740 μs, respectively. PL intensity of the individual rare earth doped samples was compared with commercial red and green phosphors. It was found that the emission from Eu doped titanate sample was 46% of the commercial red phosphor and in case of the Tb samples it was 30% when excited at 230 nm. However, the synthesized Eu doped titanate sample showed better color purity as compared to the commercial phosphor. The titanate host was doped with all the three rare earths to get white light emission from the system. The individual rare earth ion content was optimized so as to get a near white light emission. The color coordinates of the triple doped systems were evaluated and plotted on the CIE x – y diagram. Our results suggest that lithium titanate has enough potential to be a phosphor material.

Synthesis and photoluminescence (PL) investigations of lithium metasilicate doped with Eu3+, Tb3+ and Ce3+ were carried out. PL spectra of Eu-doped sample showed peaks corresponding to the 5D0→7Fj (j=1, 2, 3 and 4) transitions under ultraviolet excitation. Strong red emission coming from the hypersensitive 5D0→7F2 transition of Eu3+ ion suggested the presence of the dopant ion in structurally disordered environment. Tb3+-doped silicate sample showed blue–green emission corresponding to the 5D4→7Fj (j=6, 5 and 4) transitions. Ce-doped sample under excitation from UV, showed a broad emission band in the region 350–370 nm with shoulders around 410 nm. The fluorescence lifetimes of Eu3+ and Tb3+ ions were found out to be 790 and 600 μs, respectively. For Ce3+, the lifetime was of the order of 45 ns. PL spectra of the europium- and terbium-doped samples were compared with commercial red (Y2O3:Eu3+) and green (LaPO4:Tb3+) phosphors, respectively. It was found that the emission from the doped silicate sample was 37% of the commercial phosphor in case of the Tb-doped sample and 8% of the commercial phosphor in case of the Eu-doped sample.

Defect centers induced by gamma irradiation in Ce doped BaBPO 5 were investigated using EPR spectroscopy. From EPR studies, three phosphorous centered radicals were characterized on the basis of observed 31 P hyperfine splitting and g values as PO 4 2 - , PO 2 2 - and PO 4 4 - radicals. In addition to this, two types of boron oxygen hole centers (BOHC) and O − were also formed at room temperature. An intense broad signal in sample annealed in argon ( g ⊥ = 1.9258 and g ‖ = 1.8839) was assigned to Ce 3+ ions associated with the electron trapped at anion vacancy or nearby lattice defect. TSL studies showed two glow peaks, a relatively weaker one at 425 K and an intense one at 575 K. Spectral studies of the TSL glow peaks have shown that Ce 3+ ion acts as emission center. From the temperature dependence of the EPR spectra of gamma irradiated samples, the glow peaks at 425 K and 575 K were attributed to thermal destruction of PO 4 2 - /O − and BOHC, respectively, by trapping of electrons from elsewhere. The energy released in electron hole recombination process is used for the excitation of Ce 3+ ions resulting in these glow peaks at 425 K and 575 K. The spectral studies of the TSL glow peaks have shown emission at 330 nm indicating Ce 3+ acts as the luminescent centre. The trap depth and the frequency factor for the 425 K and 575 K peaks were determined using different heating rates method.

Thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) studies were carried out on gamma-irradiated europium-doped yttrium borate samples in the temperature range 300–600 K. TSL studies showed the presence of two glow peaks, a relatively weaker one at 390 K and an intense one at around 550 K. Room-temperature EPR spectrum of irradiated samples revealed the formation of two hole trapped radicals, namely, BO32− and O2−. Temperature variation studies showed drastic reduction in the EPR signal intensities of these radicals around 390 and 550 K indicating thermal destruction of O2− and BO32− radicals, respectively. The observed TSL emission is caused by the recombination of thermally released holes from O2− and BO32− radical ions with electrons. The energy released in electron-hole recombination process is used for the excitation of Eu3+ ion resulting in TSL glow peaks. TSL emission studies confirmed that Eu3+ acts as luminescent center for both the peaks.

In this paper, the phase equilibria of LiF-BaF2 and LiF-EuF3 systems under short-annealed and slow-cooled conditions have been explained. In these two systems, LiBaF3 and LiEuF4 exist as the line compounds in the respective systems under the present experimental conditions. The thermally stimulated luminescence (TSL) properties of EuF3 doped LiBaF3 compositions are investigated after irradiation with γ-ray. A typical glow peak at 390 K is observed in these samples, intensity of which increases up to 0.5 mol% of Eu3+ doping and then decreases due to concentration quenching. An intense glow peak at 540 K observed only in 1.0 mol% doped sample. Spectral studies of the TSL glows confirm Eu3+ ions as the luminescent centers.

Electron paramagnetic resonance (EPR), thermally stimulated luminescence (TSL), photoacoustic spectrometric (PAS) and fluorescence studies were conducted on gamma-irradiated MgB4O7: Tm phosphor. EPR spectra of irradiated samples revealed the formation of BO 3 2 - , a hole-trapped radical at room temperature. The principal values for the g and A tensors are g ∥ ≈ 2.0071 , g ⊥ = 2.0131 and A ∥ ≈ 14 G , A ⊥ = 7 G , respectively. In addition to this, the radical without any hyperfine structure was identified as O 2 - ( g ∥ = 2.0385 and g ⊥ = 2.0023 ). TSL studies showed the presence of an intense glow peak around 470 K and a weak shoulder at 550 K. Temperature dependence studies of the EPR signals in the range 300–600 K showed the thermal destruction of BO 3 2 - radical around 470 K. The observed TSL emission is caused by the recombination of thermally released holes from BO 3 2 - radical with Tm 2 + ion. The energy released in the electron–hole recombination process is used for the excitation of Tm 3 + resulting in a prominent glow 470 K. TSL emission studies confirmed that Tm 3 + acts as luminescent center for the prominent peak at 470 K. The trap depth for this peak has been determined to be 0.975 ± 0.03 eV from both TSL and EPR methods.

Europium-ion doped strontium pyrophosphate was prepared via a chemical precipitation method to investigate the fluorescence of europium ions, the phosphate radical ions formed upon gamma-ray irradiation and their role in the thermally stimulated luminescence (TSL) of this compound. Fluorescence spectra revealed that europium ions were present in divalent as well as trivalent oxidation states. The measurements of fluorescence life time indicated that Eu{sup 3+} ions existed in two different types of environments in the lattice. Gamma irradiated europium-ion doped Sr{sub 2}P{sub 2}O{sub 7} showed the presence of two thermo-luminescence glow peaks at 465 and 565 K; however, no glow was observed in the undoped sample. Electron paramagnetic resonance (EPR) studies of europium-ion doped samples showed signals from Mn{sup 2+} ions (present as impurity) prior to and after gamma irradiation. Upon gamma irradiation, signals originating from PO{sub 2}{sup 2-}, PO{sub 3}{sup 2-} and O{sub 2}{sup -} radical ions were observed in the undoped and doped samples. In the gamma irradiated europium-ion doped samples, additional low-field EPR signals, attributed to Eu{sup 2+} ions, were observed. By correlating the TSL and EPR results on europium-ion doped Sr{sub 2}P{sub 2}O{sub 7}, the mechanism for the glow peak at 565 K was identified.

Electrical conductivity and gas sensing properties of MoO3 are investigated. The electrical conductivity is found to be independent of oxygen partial pressure in the temperature range 510–773 K. Two distinct conduction processes were identified from the conductivity experiments carried out under ambient air, moist oxygen, and moist argon. The conductivity in the low temperature range (510–578 K) are attributed to species arising from the reversibly inserted water molecules into MoO3 lattice. The conduction process in the high temperature region (578–773 K) are attributed to the non-stoichiometry existing in the sample due to the presence of Mo5+ ions which was confirmed by EPR and XPS investigations. Sensing characteristics of MoO3 towards NH3, H2, and LPG were studied. Experiments showed that the ammonia sensing mechanism of MoO3 involved the formation of molybdenum suboxides and nitride.

Thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) investigations were carried out on gamma irradiated SrBPO5 samples doped with CeO2 and co-doped with CeO2 and Sm2O3. On gamma-irradiation at room temperature, BO32-, O2- and O- radicals were produced. It was seen that the O- radical ion disappeared in the sample annealed at 500 K. It is proposed that the recombination between trapped electrons and O- radical ions results in transfer of recombination energy to the impurity centre Ce3+ resulting in TSL glow peak at 485 K. In the case of co-doped samples energy transfer occurs between Ce3+ to Sm3+ resulting in increase in the intensity of glow peak at 485 K.

Rare earth and actinide doped alkali and alkaline earth sulphates, exhibit a variety of point defects stabilized due to the charge imbalance/self-irradiation and they play an important role in luminescence properties. In this paper, we report the point defects formed in the mixed sulphate K3Na(SO4)2 on doping with the radio-active rare earth element 147 Pm as studied by TSL and EPR techniques. EPR studies on self and gamma irradiated samples showed the signal due to the radical pair, SO4−–SO3− in addition to the signals from SO4−, SO3− and O2− ions. However EPR spectra of electron beam irradiated (undoped) K3Na(SO4)2 samples did not show the presence of the radical pair SO4−–SO3−, indicating the importance of dopant per se, in stabilizing the radical pair. EPR studies of 147 Pm doped samples annealed at different temperatures after gamma irradiation showed that SO4−–SO3− radical pair gets destroyed around 550 K , whereas SO4− ion gets annealed in the temperature range 375– 450 K . SO3− ion was found to be stable upto 600 K . From TSL–EPR correlation, it is inferred that the release of trapped hole at SO4− ion on heating leads to the formation of SO 4 2− ∗ and energy transfer to Pm3+ ion, results in the glow peak at 415 K .

Thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) studies on uranium doped calcium phosphate yielded mechanistic information on the observed glow peaks at 365, 410 and 450 K. TSL spectral studies of the glow peaks showed that UO2 2+ acts as the luminescent center. Electron paramagnetic resonance studies on gamma-irradiated samples revealed that the predominant radiation induced centers are H0, PO4 2-, PO3 2- and O- ion. Studies on the temperature dependence studies of the EPR spectra of samples annealed to different temperatures indicate the role of H0 and PO4 2- ions in the main glow peak at 410 K.

Electron paramagnetic resonance studies were conducted on synthetic calcium hydroxy apatite samples co-doped with 239Pu and carbonate ion. These investigations were carried out to assess the self-irradiation effects in bone and teeth on exposure to plutonium, as calcium hydroxy apatite is the major constituent of bone and teeth. On self-irradiation, in addition to the signal from O- ion arising from the radiolysis of hydroxide ion, EPR signals due to CO2-, PO22- and another signal assigned to surface O- ions were observed in the samples. In freshly quenched gamma irradiated samples, signals from CO3-, O- , PO22- and O2- ions were observed. The EPR signal of O2- ion shows a doublet splitting suggesting that O2- ion gets preferentially stabilized close to Pu4+. The radiation damage due to Pu4+ at Ca2+ sites, in the sample appears to be lower as compared to that due to external gamma-irradiation. Moreover, the alpha-dose in 239Pu doped samples has self-annealing effects. These are attributed to localized radiation damage due to alpha-particles compared to evenly distributed radical ions produced due to gamma-irradiation.

Thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) studies were carried out on cerium doped and cerium–uranium co-doped K 3 Na(SO 4 ) 2 samples after γ -irradiation. Three glow peaks around 352, 415 and 475 K were observed and their spectral characteristics have shown that Ce 3+ and UO 2 2+ act as the emission centres in K 3 Na(SO 4 ) 2 :Ce and K 3 Na(SO 4 ) 2 :Ce, U, respectively. In Ce–U co-doped sample, energy transfer from cerium to uranium takes place. The commonly occurring radiation-induced centres in sulphates, viz SO 3 − and SO 4 − were observed by EPR and SO 4 − radical ion was found to take part in the TSL emission at 415 K . The hitherto unknown information, however, is the formation of SO 4 − –SO 3 − radical pair creating deep traps in these lattices, apparently assisted by the dopants. This is the first observation of such radical pair formation leading to the identification of deep traps in this lattice. The radical pair, (SO 3 − –SO 4 − ) which is stable up to 970 K , decreases the intensity of the peak at 415 K due to the depletion of SO 4 − centres.

Thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) studies were conducted on self-irradiated as well as gamma irradiated BaCO 3 co-doped with 237 Np 4+ and NO 3 − ions. EPR studies of the irradiated samples revealed that the electron transfer process between iso-electronic carbonate and nitrate groups is the dominant effect of ionizing radiation, forming CO 3 − and NO 3 2− ions. This facilitated the radiation stability of the valence of Np in the tetravalent state. TSL spectral studies showed that Np 4+ ion acts as the luminescence centre. TSL–EPR correlation studies revealed the role of CO 3 − ion in the glow peak at 413 K .

Thermally stimulated luminescence (TSL), electron paramagnetic resonance (EPR) and photo-acoustic spectroscopy (PAS) techniques were used to investigate the radiation induced centers in polycrystalline LaBa2F7 containing trace amounts of other rare-earths particularly Gd3+ and Sm3+. The TSL glow curve of LaBa2F7 after g-irradiation to a dose of 3 kGy had shown a weak TSL glow peak at 390 K and a much stronger one at 495 K. The EPR spectra of the g-irradiated LaBa2F7 samples showed the presence of O- and O2 - ions. Temperature dependence study of the EPR spectra showed that the thermal destruction of O- ion occurs in the 460-490 K temperature range. In g-irradiated samples, O- and F-centers were identified by PAS. The correlation of EPR and PAS results indicate that the prominent TSL glow at 495 K is associated with the thermal destruction of O- radical ion. The trap parameters viz. trap depth and frequency factor have been determined from TSL data.

Electron paramagnetic resonance (EPR) evidence is presented for the radiation stabilization of pentavalent uranium in CaO matrix. From the theoretical predictions ofg value for U5+ in axial symmetries, it was concluded that U5+ at Ca2+ site is associated with a second neighbour charge compensating Ca2+ vacancy. EPR measurements also revealed the presence of Mn2+, Mn4+ and Cu2+ impurities in the samples. The thermal stability of U5+ was investigated using EPR and thermally stimulated luminescence (TSL) techniques. The TSL and EPR studies on gamma irradiated uranium doped calcium oxide samples had shown that the intense glow peak at 540 K is associated with the reduction in the intensity of EPR signal of U5+ ion around this temperature. This peak is associated with the process U5++hole→U6+*→U6++hv. The activation energy for this process was determined to be 1.4eV.

The electron/hole trapped centres created during internal irradiation in239Pu doped K2Ca2(SO4)3 were investigated using electron paramagnetic resonance (EPR), thermally stimulated luminescence (TSL) and photoacoustic spectroscopic studies (PAS). These techniques were used to identify the defects and characterize the thermally induced relaxation processes. TSL studies of self (α)/γ-irradiated239Pu doped K2Ca2(SO4)3 revealed two glow peaks around 400 and 433K. Plutonium introduced as Pu4+ was partly reduced to Pu3+ due to self irradiation. This was ascertained from PAS studies. EPR studies carried out on these samples showed the formation of radical ions SO 4 − , SO 3 − , O 3 − , etc. The thermal destruction of SO 4 − ion was found to be associated with the prominent glow peak around 433K. Pu3+ was found to act as luminescent centre for the observed TSL glow. The trap depth for the glow peak at 433K has been determined from TSL and EPR data.

Thermally stimulated luminescence (TSL) studies of gamma-irradiated uraniumdoped K2Ca2(SO4)3 revealed two glow peaks around 400 K and 435 K. Electron paramagnetic resonance (EPR) studies carried out on these samples have shown the formation of the radical ions SO 4 − , SO 3 − , SO 2 − and O 3 − . From the study of the thermal stabilities of these radical ions, it was found that the thermal destruction of SO 2 − and SO 4 − radical ions are associated with the glow peaks observed around 400 K and 435 K respectively. Uranate ion was identified as the luminescent centre for the observed TSL glow. The trap depth values for the glow peaks have been determined from TSL data.

Electron paramagnetic resonance (EPR) studies of γ-irradiated uranium doped BaCO3 have shown the formation of CO3−, CO2−, O3− and O2− ions. Thermally stimulated luminescence (TSL) glow curves of the γ-irradiated samples in the 300–600 K range have exhibited an intense peak around 360 K and a weak one around 440 K. The trap parameters for these peaks have been determined from TSL data. Spectral studies of the glow have revealed emission around 566, 583 and 590 nm characteristic of the uranate ion. From studies on the thermal stabilities of the radical ions, it has been inferred that the glow peak around 360 K is associated with the thermal destruction of O2− ion and the peak around 440 K is associated with the thermal destruction of CO3− ion.

Thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) studies were carried out on samples of 237Np4+ doped CaSO4/SrCO4. TSL glow peaks with Tmax around 395 and 425 K in CaSO4, and 425 K in SrSO4, were observed on samples gamma-irradiated at 300 K. The prominent TSL around 425 K in CaSO4/SrSO4 was found to coincide with the temperature at which the EPR signals of SO4− radical ions diasappear. The trap depth value for this process has been determined from both TSL and EPR data. A comparison is made of the trap depth values obtained for “hole” detrapping at the sulphate site in various actinide doped CaSO4/SrSO4 lattices studied in our laboratory. The average activation energy was found to be in the range 0.8–0.9 eV.

Un-doped as well as Tm doped strontium borate glasses were prepared and characterized by different spectroscopic techniques. 11B MAS-NMR studies on the glass samples have shown the presence of BO3 structural units in addition to the tetrahedrally coordinated BO4 structural units confirming glass formation. Optical absorption and photoluminescence studies of these samples showed stabilization of thulium as Tm3+ ions in the virgin sample, while, on γ-irradiation, partial reduction to Tm2+ was observed. EPR investigations of virgin and γ-irradiated samples showed the presence of BO 3 2 - centered radicals in the latter samples only. TSL studies of γ-irradiated Tm doped strontium borate glass showed two glow peaks around 423 and 528 K. Tm3+ was identified as the luminescent center from spectral studies. Temperature dependence studies of EPR spectra have shown the thermal destruction of BO 3 2 - radical ion to be associated with the TSL glow peak at 423 K. Based on these investigations, the mechanism for the processes occurring during γ-irradiation and subsequent thermal treatment is proposed.

Electron paramagnetic resonance [EPR] and thermally stimulated luminescence [TSL] studies were conducted on self [α]-irradiated239Pu doped calcium chloro phosphate andγ-irradiated239Pu/238UO22+ doped calcium chloro phosphate to elucidate the role of the electron/hole traps in thermally stimulated reactions and to obtain trap parameters from both TSL and EPR data. TSL glow peaks around 135 K (# peak 1), 190 K (# peak 2), 435 K (# peak 5) and 490 K (# peak 7) were observed and their spectral characteristics have shown that Pu3+ and UO66− act as luminescent centres in calcium chloro phosphate with respective dopants. EPR studies have shown the formation of the radical ions H0, PO42−, O−, O2− and [ClO]2− under different conditions. Whereas the [ClO]2− radical being stable up to 700 K, was not found to have any role in TSL processes, the thermal destruction of other centres was found to be primarily responsible for the TSL peaks observed. The trap depth values were determined both by using the TSL data and also the temperature variation of EPR spectra of these centres.

Electron paramagnetic resonance (EPR) and thermally stimulated luminescence (TSL) studies have been carried out in sub-room temperature region in γ-irradiated BaCO 3 : 241 Am phosphor. CO - 2 and CO - 3 radical ions are found to get stabilised at 77 K. Whereas CO - 2 radical was found to be stable upto room temperature. CO - 3 was found to get destroyed around 170 K coinciding with the occurrence of a TSL glow peak at that temperature.

Thermally stimulated luminescence (TSL) studies were conducted on 239 Pu- and 241 Am-doped NaCl and KCl. Both self-irradiated (by α-particles) as well as externally γ-irradiated samples were investigated. In general, the TSL glow curves were found to be similar under these two irradiation conditions for both types of samples. In addition to the intrinsic emission of the host lattices, characteristic emissions of Pu 3+ /Am 3+ were also observed in the 239 Pu/ 241 Am doped alkali halides. The main glow peaks observed above room temperature are associated with the partial thermal destruction of radiation-induced F -centres and the total destruction of F - and M -centres. The trap parameters for the different glow peaks have been determined.

Trap level spectroscopy studies of alkaline-earth sulphate (CaSO4 and SrSO4) phosphors doped with 239Pu were carried out using electron paramagnetic resonance (EPR) and thermally stimulated luminescence (TSL) techniques. Internal (in situ) alpha -irradiation (from the alpha -decay of 239Pu) and external gamma -irradiation studies carried out using EPR revealed the formation of radicals SO2-, O-, O3-, SO4-, etc, in these matrices under different conditions. SO2- dimer formation is detected for the first time in alkaline-earth sulphates on gamma -irradiation at 77 K. The thermal stabilities of the radical ions (monitored using EPR) and their correlation with TSL glow peaks helped to identify the thermally stimulated free-radical reactions which result in luminescence and were characterised by the activation energy and frequency factor obtained from the analysis of TSL glows.

For pt.I see ibid., vol.17, p.5851 (1984). Trap-level spectroscopic studies of SrSO4 phosphor doped with 241Am were conducted using ESR and thermally stimulated luminescence (TSL) techniques. The formation of electron and hole traps due to internal alpha -irradiation (from the decay of 241Am) and external gamma -irradiation were distinguished by carrying out the studies on pure SrSO4 and also on SrSO4 doped with europium (lanthanide analogue of Am). The ESR studies on these samples have shown that the paramagnetic radicals SO4-, SO3-, O3-, S5+, SH2- were stabilised in SrSO4 under different dopant and irradiation conditions. The radical SH2- is detected for the first time. From the ESR studies of thermal stabilities of radical ions produced and their correlation with TSL peaks, the role of paramagnetic molecular species in the electron and hole trapping and thermally stimulated free radical reactions were identified and the corresponding activation energies and frequency factors were determined.

Electron paramagnetic resonance (EPR) and thermally stimulated luminescence (TSL) studies were conducted onγ-irradiated CaSO4:UO 2 2+ to elucidate the role of the electron/hole traps in thermally stimulated reactions and to obtain the trap parameters (trap depth and frequency factor). Intense TSL glow peaks around 140, 375, 400 and 438±2K are observed and their spectral characteristics have shown that UO 2 2+ and UO 6 6− act as luminescent centres. EPR studies have shown the peaks at 140 and 400/438K to be associated with the thermal destruction of O− and SO 4 − radical ion in two stages respectively. The maximum rate of thermal destruction of SO 4 − ions (as seen by EPR) in various alkaline earth sulphate matrices investigated in our laboratory is also summarized. The activation energy which characterizes the electron transfer reaction between SO 4 − and the dopant ion lies in the range of (0.95±0.15 eV). This value is independent of the dopant and therefore seems to be characteristic of the binding energy of hole in the SO 4 − radical ion.