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Lu2O3:Pr,Hf ceramics were investigated using mainly thermoluminescence (TL) technique. Their ability to efficiently store energy acquired upon irradiation with X-rays was proven. The best TL performance was achieved for compositions containing 0.025%-0.05% of Pr and about 0.1% of Hf. Further enhancement of TL efficiency was attained by increasing the temperature of sintering of the ceramics up to 1700 °C and applying reducing atmosphere of forming gas. It was also proven that fast cooling after the sintering at 1700 °C significantly enhanced the storage phosphor performance. TL glow curve contained three components peaking around 130, 250 and 350 °C. Among them, the one at 250 °C contributed the most to the total TL. [ABSTRACT FROM AUTHOR]

White-light persistent luminescence is of practical interest but is not easy to generate, especially over a longer time. In this paper we present the possibility to generate a white-light persistent emission over a few hours by the doubly-doped La 2 Hf 2 O 7 :Ti,Pr phosphor. Its relevant thermoluminescent properties are presented together with adequate photoluminescence characteristics. The singly-activated versions (with Ti or Pr) of the La 2 Hf 2 O 7 host were also fabricated and characterized for comparison and better understanding the properties of La 2 Hf 2 O 7 :Ti,Pr. Thermoluminescence of all those phosphors showed strong activator-concentration dependence. When the activator contents exceeded 0.1mol% the thermoluminescence intensity lessened quickly and the persistent luminescence intensity and duration got reduced adequately. In La 2 Hf 2 O 7 :0.1%Ti,0.1%Pr both activators contributed to strong thermoluminescence peaking at around 115 °C and resulting from traps showing some distribution of depths. After charging, these traps served as reservoir of energy for white persistent luminescence generated by both Ti and Pr activators and lasting a few hours. • White photo- and persistent luminescence of La 2 Hf 2 O 7 :Ti, Pr ceramics is presented. • (Ti,Pr) double doping of La 2 Hf 2 O 2 simplifies the thermoluminescence glow curve. • Thermoluminescence glow peak of La 2 Hf 2 O 2 :Ti, Pr at 110 °C favors long persistent luminescence generation. [ABSTRACT FROM AUTHOR]

Abstract: Eu-doped barium hafnate powders, BaHfO3:Eu, prepared with ceramic method have quite peculiar spectroscopic properties, which can be significantly altered changing the dopant concentration as well as preparation atmosphere. When synthesis is performed in a reducing atmosphere, a fraction of Eu gets reduced and produces a broad-band emission peaking around 480nm. Due to a partial overlapping of the excitation spectra of Eu3+ and Eu2+ luminescence, the emission colour can vary between bluish green, when only Eu2+ is excited, red when solely Eu3+ is stimulated and white upon simultaneous excitation of both Eu3+ and Eu2+ activator ions around 290nm. Upon X-ray excitation only Eu3+ luminescence is produced. Radioluminescence of undoped BaHfO3 consists of a broad-band peaking around 410nm, which disappears when Eu enters the host. Materials prepared in a reducing atmosphere do not show any phase separation even for higher Eu concentrations. [Copyright &y& Elsevier]

Abstract: Raw powders of BaHfO3:Ce were prepared with modified Pechini process and were calcined in the 650–1700°C range of temperatures, at different atmospheres – air, vacuum and nitrogen–hydrogen mixture. The powders were converted into sintered ceramics by vacuum sintering. The materials were characterized by XRD, TEM, photoluminescence and radioluminescence spectroscopy. UV-VUV excitation spectra were recorded using synchrotron radiation. Excitation spectra proved that atmosphere of preparation significantly influences the host-to-activator energy transfer, which is the most efficient for materials made in reducing conditions. Also radioluminescence efficacy was found to be superior for materials prepared in such conditions. [Copyright &y& Elsevier]

Abstract Thermoluminescent properties and energy storage characteristics of Lu 2 O 3 :Tb,M (M = Hf, Ti, Nb) sintered ceramics induced by ionizing radiation are presented and discussed. Dose-response dependence, radiation hardness and fading are studied. A linearity of the former exceeding seven orders of magnitude is confirmed for Lu 2 O 3 :Tb,Hf and Lu 2 O 3 :Tb,Nb ceramics. Lu 2 O 3 :Tb,Hf shows the best TL performance and also its fading is the lowest reaching 15% over 7 h and shows tendency to saturate. During the same period of time the Lu 2 O 3 :Tb,Ti, despite having TL at higher temperatures, losses about 25% of the stored energy and the TL signal of Lu 2 O 3 :Tb,Nb fades by almost 40% over 7 h. First order TL kinetics is confirmed for all three compositions. A self-dose effect in Lu 2 O 3 :Tb,Hf due to a natural content of the radioactive isotope (2.6%) is proved to be important for long-time reading of low doses. Graphical abstract Image 1 Highlights • Thermoluminescent properties of Lu 2 O 3 :Tb,M (M = Hf,Ti,Nb) comprehensively compared. • Linear dose-response dependence exceeding as much as seven orders of magnitude. • Extreme radiation hardness proved. • Self-dose of the radioactive 176Lu on TL quantitatively studied. [ABSTRACT FROM AUTHOR]

Abstract: Lu2O3:Tb,Hf ceramics containing 0.1% of Tb and 0–1.5% of Hf were prepared in reducing atmosphere at 1700°C and their thermoluminescence properties were systematically studied. For comparison Tb,Ca co-doped specimen was also fabricated and investigated. The Tb,Hf ceramics shows basically a single TL band located around 180°C as found with heating rate of 15°C/min. Ceramics singly doped with Tb show complex TL glow curves indicating the presence of traps of very different depths. On the other hand Tb,Ca co-doping is beneficial for the development of shallow traps with the main TL band around 70°C. Hence, the aliovalent impurities, Ca2+ and Hf4+, strongly influenced the traps structure in Lu2O3:Tb ceramics, each of them in its own specific way. Isothermal decay of Lu2O3:Tb,Hf at 185°C was recorded and its shape suggest that multiple hole trapping occurs in the Lu2O3:Tb,Hf ceramics. Due to the different traps depths the Lu2O3:Tb,Hf ceramics possess properties typical for storage phosphors, while Lu2O3:Tb,Ca is a persistent luminescent material rather. [Copyright &y& Elsevier]

Radio- and thermoluminescent properties of HfO 2 :Ti sintered ceramics were investigated in the temperature range of 10–300 K. Fabrication atmosphere altered somewhat the efficiency of radioluminescence but did not affect the spectral distribution of the broad scintillation band covering the 380–570 nm range of wavelengths and peaking at 522 nm at 10 K and about 490 nm at 300 K. The analogous shift was seen in photoluminescence. Scintillation efficiency was continuously growing from 10 K to 300 K, while photoluminescence intensity was stable in the 10–250 K range of temperatures and was reduced by about 30% at 300 K. Analysis of these observations allowed to conclude that diffusion of carriers generated upon the impact of high-energy photons towards the Ti emitting center is strongly temperature-dependent and inferior at lower temperatures. Upon exposure to X-rays at 10 K the ceramics stored more than 50% of the absorbed energy. This energy could be recovered later upon thermal stimulation of the ceramics. Four main thermoluminescent peaks were then produced at 95, 140, 243 and 278 K. This effect was tentatively associated with theoretically predicted self-trapping of holes in HfO 2 . The so-called partial cleaning and T max –T stop experiments indicated that some fraction of traps shows a continuous distribution of their depths. [ABSTRACT FROM AUTHOR]