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Phototransferred thermoluminescence (PTTL) of natural fluorite induced by 470 nm blue-, 525 nm green-, and 870 nm infrared light is reported. Although its conventional thermoluminescence (TL) glow curve measured during heating to 600 °C has six peaks, only five are reproduced under phototransfer. One of them corresponds to a hole trap. The sixth peak counterintuitively increases in intensity with illumination in a change suggestive of competition effects involving deep electron traps. The dependence of PTTL intensity on duration of illumination for each PTTL peak is analyzed using phenomenological and kinetic models as systems of acceptors and donors with the number of the latter informed by experiment. The intensity of PTTL increases with the temperature of illumination with an activation energy of thermal assistance of 0.14 ± 0.01 eV and decreases at elevated temperatures with an activation energy of thermal quenching of 1.1 ± 0.3 eV. The long-term behavior of time-response profiles and the interaction of holes with stimulated electrons as studied by stability theory show unstable critical points. Supplementary tests show that exposing CaF2 to UV illumination achieves the same effect as beta irradiation, and any resultant peaks relate to conventional TL rather than phototransfer. [ABSTRACT FROM AUTHOR]

Phototransferred thermoluminescence (PTTL) of Al2O3:C,Mg induced by 470 nm blue, 525 nm green, and 870 nm infrared light is reported. Although its conventional TL glow curve measured during heating to 600 °C has seven peaks (labeled I–VII), only peak II is reproduced under phototransfer, except when the sample is preheated to 180 °C when peak IV also re-appears. The dependence of PTTL intensity on the duration of illumination for both PTTL peaks is analyzed using phenomenological and kinetic models as systems of acceptor and donors, with the number of the latter determined by experiment. The intensity of PTTL increases with the temperature of illumination with an activation energy of thermal assistance of either 0.015 ± 0.002 or 0.047 ± 0.002 eV when either 470 or 525 nm light is used but decreases at elevated temperatures with an activation energy of thermal quenching equal to 0.51 ± 0.02 eV independent of illumination wavelength. The long term behavior of time-response profiles for a system of one acceptor and a single donor, as an exemplar, as studied by stability theory, shows an unstable critical point. Mechanisms for the PTTL are discussed and the emission is ascribed to electron centers in the oxygen sub-lattice. [ABSTRACT FROM AUTHOR]

Phototransferred thermoluminescence (PTTL) from BeO is reported. The conventional TL glow curve has five peaks, I–V, at 50, 182, 283, 437, and 535 °C when measured at 1 °C s−1 The dominant one is peak II. Only the first three reappear under phototransfer. Electron traps for peaks IV and V weakly contribute to the PTTL. The PTTL at peak III, supposedly associated with these weak donors, is counterintuitively intense. All PTTL peaks are affected by light-induced fading, thermal quenching, and all but peak II by thermal fading. The activation energy for thermal quenching was found as 0.56 ± 0.02 , 0.53 ± 0.05 , and 0.94 ± 0.07 eV using peaks I, II, and III, respectively. Electronic processes relevant in the PTTL of BeO are discussed. PTTL time-response profiles are analyzed using systems of coupled linear differential equations as well as by theoretical modeling. [ABSTRACT FROM AUTHOR]

Sr4Al14O25:Eu2+,Dy3+ is a commercially available green light emitting persistent luminescent phosphor. Owing to its complex crystalline structure and induced point defects, it shows fascinating luminescence that persists to typically up to 18 hrs after excitation. We report a trap-spectroscopic analysis of Sr4Al14O25:Eu2+,Dy3+ using thermoluminescence (TL). A TL glow curve measured at 1 °C/s following irradiation to 2 Gy at 20 °C shows two maxima at ~64 (labelled as P1) and 252 °C (P2). The variation of integrated TL intensity as a function of heating rate shows competition between radiative and non-radiative recombination processes. Beyond 1 °C/s heating rate, the non-radiative recombination process dominates and the luminescence efficiency drops sharply beyond 100 °C. The activation energy for thermal quenching is estimated to be W = 0.69 ± 0.07 eV. The peak maxima of P1 and P2 after correction for thermal quenching are found at ~70 and 275 °C. In addition, a secondary peak appears on the high temperature side of P1. Both the peaks show a gradual shift in their peak position Tm towards high temperature with preheating temperature Tstop. Moreover, the peaks also show a similar shift in Tm towards high temperature with increase in irradiation temperature Tirr. This suggests that peaks P1 and P2 are combinations of several closely spaced overlapping components. The activation energy of the component peaks comprising P1 is estimated to be ~0.63 - 0.68 eV whereas that of the component peaks comprising P2 is ~1.22 - 1.65 eV. An analysis of the fractional area between a pair of glow curves measured from the sample irradiated at different temperatures (Tirr) shows that the trap distribution associated with peak P1 is non-Gaussian whereas that associated with peak P2 follows Gaussian distribution. [ABSTRACT FROM AUTHOR]

Polycrystalline CaTa2O6:Pr3+ phosphor is prepared by calcination of a stoichiometric mixture of Ta2O5 and CaCO3 plus a 0.5 mol% PrCl3 dopant level (1200 °C, 4 h). [ABSTRACT FROM AUTHOR]