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Here we present the cascade converter (CC), which provides real-time imaging of ionizing radiation (IoR) distribution. It was designed and manufactured with the simplest architecture, utilizing liquid crystal display (LCD) technology. Based on two merged substrates with transparent electrodes, armed with functional layers, with the cell filled with nematic liquid crystal, a display-like, IoR-stimulated CC was achieved. The CC comprises low-absorbing polymer substrates (made of polyethylene terephthalate—PET) armed with a transparent ITO electrode covered with a thin semipermeable membrane of polymer (biphenylperfluorocyclobutyl: BP-PFCB) doped with functional nanoparticles (NPs) of Lu2O3:Eu. This stack was covered with a photoconductive layer of α-Se and finally with a thin polyimide (PI) layer for liquid crystal alignment. The opposite substrate was made of LCD-type glass with ITO and polyimide aligning layers. Both substrates form a cell with a twisted structure of nematic liquid crystal (TN) driven with an effective electric field E e f f . An effective electric field driving TN structure is generated with a sum of (1) a bias voltage V B I A S applied to ITO transparent electrodes and (2) the photogenerated additional voltage V X r a y induced between ITO and α-Se layers with a NPs-doped BP-PFCB polymer layer in-between. The IoR (here, X-ray) conversion into real imaging of the IoR distribution was achieved in the following stages: (1) conversion of IoR distribution into non-ionizing red light emitted with functional NPs, (2) transformation of red light into an electric charge distributed in a layer of the photoconductive α-Se, which is what results in the generation of distributed voltage V X r a y , and (3) a voltage-mediated, distributed switching of the TN structure observed with the naked eye. The presented imaging device is characterized by a simple structure and a simple manufacturing process, with the potential for use as a portable element of IoR detection and as a dosimeter. [ABSTRACT FROM AUTHOR]

Aluminum garnets display exceptional adaptability in incorporating mismatching elements, thereby facilitating the synthesis of novel materials with tailored properties. This study explored Ce3+-doped Tb3Al5−xScxO12 crystals (where x ranges from 0.5 to 3.0), revealing a novel approach to control luminescence and photoconversion through atomic size mismatch engineering. Raman spectroscopy confirmed the coexistence of garnet and perovskite phases, with Sc substitution significantly influencing the garnet lattice and induced A1g mode softening up to Sc concentration x = 2.0. The Sc atoms controlled sub-eutectic inclusion formation, creating efficient light scattering centers and unveiling a compositional threshold for octahedral site saturation. This modulation enabled the control of energy transfer dynamics between Ce3+ and Tb3+ ions, enhancing luminescence and mitigating quenching. The Sc admixing process regulated luminous efficacy (LE), color rendering index (CRI), and correlated color temperature (CCT), with adjustments in CRI from 68 to 84 and CCT from 3545 K to 12,958 K. The Ce3+-doped Tb3Al5−xScxO12 crystal (where x = 2.0) achieved the highest LE of 114.6 lm/W and emitted light at a CCT of 4942 K, similar to daylight white. This approach enables the design and development of functional materials with tailored optical properties applicable to lighting technology, persistent phosphors, scintillators, and storage phosphors. [ABSTRACT FROM AUTHOR]

Li2SO4 or (Li2SO4 + SiO2)-mixture fluxes were used to prepare a Lu2O3:Eu powder phosphor as well as an undoped Lu2O3 utilizing commercial lutetia and europia as starting reagents. SEM images showed that the fabricated powders were non-agglomerated and the particles sizes varied from single microns to tens of micrometers depending largely on the flux composition rather than the oxide(s)-to-flux ratio. In the presence of SiO2 in the flux, certain grains grew up to 300-400 μm. The lack of agglomeration and the large sizes of crystallites allowed making single crystal structural measurements and analysis on an undoped Lu2O3 obtained by means of the flux technique. The cubic structure with a = 10.393(2) Å, and Ia3 space group at 298 K was determined. The most efficient radioluminescence of Lu2O3:Eu powders reached 95%-105% of the commercial Gd2O2S:Eu. [ABSTRACT FROM AUTHOR]

Sintered nanoceramics of Pr-doped lanthanum hafnate, La2 Hf2 O7: Pr, were prepared by means of a high-pressure sintering technique using nanopowders made by Pechini method. Structure, morphology, and spectroscopic properties of the ceramics compared to the starting powder are presented and discussed. Emission and excitation spectra recorded at room temperature as well as at 7 K using synchrotron radiation are presented together with results of luminescence kinetics measurements. In ceramics, at 7 K, the Pr3+ luminescence from 3P0 (blue-green, green, and red region) and 1D2 (red) levels is accompanied by a broad-band emission located in the 380-530 nm range of wavelengths, whereas powders gives only the Pr3+-related luminescence. Depending on the excitation wavelength, the broad-band emission maximum moves between 430 and 470 nm indicating superposition of at least two components. In sintered nanoceramics, the lifetimes of Pr3+ emissions from 3P0 and 1D2 levels were by 10%-20% shorter compared to the powder. The existence of different luminescence centers was proved by the selective emission decays examination. The fast 5 d → 4 f luminescence of Pr3+ was not observed from either of the two types of La2Hf2O7:Pr materials. [ABSTRACT FROM AUTHOR]

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]

Abstract: Powders of calcium yttrium silicate, Ca3Y2(Si3O9)2, containing 0.1–3% Tb3+ were prepared using a sol-gel method and characterized with XRD, IR, UV–vis and UV–VUV spectroscopies at room temperature and 10K. Structural analysis revealed pure monoclinic phase of Ca3Y2(Si3O9)2 after heat-treatment at 1000°C. Infrared spectroscopy showed that between 800 and 900°C a short-range structural organization of the components proceeded, yet without crystallization. A strong emission of Tb3+ had been observed both in the green part of the spectrum due to the 5 D 4→7 F J transitions and in the blue-violet region owing to the 5 D 3→7 F J radiative relaxation. The color of the light could be tuned from yellowish-green to bluish-white both by means of the dopant content and the temperature of synthesis. Efficient luminescence of Tb3+-doped Ca3Y2(Si3O9)2 phosphors could also be obtained upon stimulation with vacuum ultraviolet synchrotron radiation demonstrating that an energy transfer from the host to the Tb3+ ions takes place. [Copyright &y& Elsevier]

Abstract: Fabrication procedure of nanocrystalline Lu2O3:Eu powders from organic–inorganic emulsion is presented and the behavior of the precipitate upon heat-treatment is analyzed. It is proved that heating at 800–850°C converts the raw material into Lu2O2SO4:Eu, which decomposes further to Lu2O3:Eu when heated at 1000°C or above. Research with synchrotron radiation revealed that free exciton is able to transfer effectively its energy to Eu3+ ions in Lu2O3:Eu nanosized powder, which is in contrast to the findings for micron-sized ceramics of the same composition. [Copyright &y& Elsevier]

Abstract: Nanocrystalline powders of Y3Al5O12:Ce (YAG:Ce) were prepared using Pechini technique and precipitation with urea at 80–90°C. It was shown that material obtained using Pechini procedure, after heating at 900–1000°C is crystallographically pure, while that made with urea is contaminated with Y4Al2O9 and YAlO3. For all powders, heating at reducing atmosphere of nitrogen–hydrogen mixture at 1000°C caused a red shift of the Ce3+ luminescence by about 20–25nm. The effect was stronger for the powder prepared with urea. Also this powder was characterized by a longer decay time of the Ce3+ emission indicating the treatment at reducing atmosphere diminished nonradiative relaxation probability of the excited electrons. [Copyright &y& Elsevier]

Abstract: Y2SiO5 doped with Ce3+ was successfully prepared at 1300°C with the aid of Li2SO4 flux. SEM and TEM images proved that the sizes of particles making-up the powder are in the range of 1–10μm. A small fraction of grains is nanosized. EDS spectra proved that the distribution of Y, Si and Ce is uniform. Luminescence spectra show typical broad Ce3+ luminescence in Y2SiO5 host, which peaks around 420nm. The emission decays with the time constant of about 40ns. [Copyright &y& Elsevier]

Aluminum garnets display exceptional adaptability in incorporating mismatching elements, thereby facilitating the synthesis of novel materials with tailored properties. This study explored Ce 3+ -doped Tb 3 Al 5-x Sc x O 12 crystals (where x ranges from 0.5 to 3.0), revealing a novel approach to control luminescence and photoconversion through atomic size mismatch engineering. Raman spectroscopy confirmed the coexistence of garnet and perovskite phases, with Sc substitution significantly influencing the garnet lattice and induced A 1g mode softening up to Sc concentration x = 2.0. The Sc atoms controlled sub-eutectic inclusion formation, creating efficient light scattering centers and unveiling a compositional threshold for octahedral site saturation. This modulation enabled the control of energy transfer dynamics between Ce 3+ and Tb 3+ ions, enhancing luminescence and mitigating quenching. The Sc admixing process regulated luminous efficacy (LE), color rendering index (CRI), and correlated color temperature (CCT), with adjustments in CRI from 68 to 84 and CCT from 3545 K to 12,958 K. The Ce 3+ -doped Tb 3 Al 5-x Sc x O 12 crystal (where x = 2.0) achieved the highest LE of 114.6 lm/W and emitted light at a CCT of 4942 K, similar to daylight white. This approach enables the design and development of functional materials with tailored optical properties applicable to lighting technology, persistent phosphors, scintillators, and storage phosphors.

A number of Lu 2 O 3 -based materials were reported to present efficient capability of trapping excited charge carriers in metastable excited states formed either by specific dopants or naturally occurring defects. Over the years, abundant experimental data have been collected, which were taken as a solid ground to treat the problem using computational chemistry. Density functional theory (DFT) calculations with an advanced meta generalized gradient approximation (mGGA) functional were used to analyze electron trapping in cubic Lu 2 O 3 doped with Hf. Individual ions of dopant and nearest-neighbor dopant ion pairs were considered. The effects of interstitial anions such as O 2- and Cl - were analyzed. In most of the analyzed cases the additional electron charge is localized at the dopant site. However, in many of the studied cases, the dopant/defect states overlap with the conduction band and cannot correspond to electron trapping. The Hf 3+ ion in the Lu site of C 3i local symmetry ({\rm Hf}^{\times}_{{\rm Lu}-C_{\rm 3i}}) corresponds to a moderate trap depth of 0.8-0.9 eV. Several composite defects corresponding to deeper (1.1-1.4 eV) traps also exist. Unambiguous deep traps (1.5-1.8 eV) correspond to systems with Hf dopant in the cationic void, accompanied by two interstitial oxygen atoms. The results thus indicate that basic `Hf-substitutes-Lu' doping is unlikely to correspond to the deep traps observed experimentally in Lu 2 O 3 :Tb,Hf andLu 2 O 3 :Pr,Hf and more complex defects must be involved.