Eu Powder Research Articles

Structure and luminescence properties of EuF3 and SrF2:Eu nanoparticles after microwave plasma annealing in "methane-hydrogen".

Recently, progress has been made in fabricating diamond-based scintillators with integrated rare-earth luminescent particles. These luminescent particles are integrated into the bulk of diamond during their synthesis by chemical vapor deposition (CVD). However, the growth conditions include a chemically aggressive plasma environment and elevated temperatures, which results in the partial degradation of particles and a decrease in the intensity of their luminescence. Here, we investigate the effect of thermal annealing of luminescent EuF3 and SrF2:Eu powders in microwave plasma that simulates the growth conditions of polycrystalline diamond. It was found that silicon substrates act as efficient reducing agents that lead to the partial reduction of trivalent europium to divalent europium. When annealing occurs on a diamond substrate, the reduction processes proceed at a significantly slower rate. The observed luminescence spectra showed both Eu2+ and Eu3+ luminescence bands, which allows for a targeted tuning of the luminescence spectrum of europium in composites and can be used to fabricate detectors and visualizers of X-ray radiation using a visible signal from the desired combination of Eu2±/Eu3± ions. During plasma annealing in pure hydrogen at moderate temperatures (600 °C), an intensive hydrogenation of particles is observed. Such hydrogen plasma treatment of fluorides may be considered a promising route to fabricate hydrides of various metals.

The effect of high temperature aging on fluorescence properties of Eu3+-doped La2(Zr0.7Ce0.3)2O7

Introduction of luminescent rare earth ions into thermal barrier coatings (TBCs) for the study of TBCs failure mechanism is a very effective non-destructive method. In this paper, Eu3+ ions were doped into La2(Zr0.7Ce0.3)2O7 (LZ7C3) to form LZ7C3:Eu fluorescent material using a high-temperature solid-phase synthesis method. By analyzing the physical structure, fluorescence properties and thermophysical properties of LZ7C3:Eu powders synthesized with different Eu3+ dopant concentrations at different temperatures, we determined that a synthesis temperature of 1400 °C, a dopant concentration of 1 mol% are the optimal synthesis conditions for LZ7C3:Eu. Independent LZ7C3:Eu coating was prepared by atmospheric plasma spraying technology, and high temperature aging test was carried out at 1400 °C. The influence of high temperature aging on the 5D0→7F2 energy level transition peak of Eu3+ in LZ7C3 powder and its coating was examined by microscopic emission spectroscopy. The results show that the peak of the 5D0→7F2 energy level transition is red-shifted, and the peak intensity and the full width at half maxima (FWHM) of the powder decrease gradually with the increase of high temperature aging time. The peak of the 5D0→7F2 energy level transition of the coating exhibits a constantly fluctuating tendency of red-shifting and then blue-shifting, and the peak intensity and the FWHM also continue to decrease. High temperature aging has a negative effect on the fluorescence properties of LZ7C3:Eu materials.

A pure tetragonal europium-doped yttrium-stabilized zirconia thermal barrier coating: Phase structure and luminescence

YSZ:Eu powder was prepared by sol spray pyrolysis method. Thermal barrier coatings (TBCs) composed of Eu3+-doped pure tetragonal yttrium-stabilized zirconia (namely, YSZ:Eu) were fabricated by air-plasma spraying technique. Crystal structure and fluorescence intensity of YSZ:Eu coating were investigated after aging at 1200 °C for 5 − 100 h. X-ray diffraction (XRD) indicates that tetragonal phase in YSZ:Eu coating had high resistance to degradation over a wide range of time periods and temperatures. Luminescence results indicate that asymmetry ratios of the fluorescence emission spectra were stable in a range of 1.2 ± 0.2. Relationships between phase structure and lattice distortion were further studied by fluorescence spectroscopy measurement using I606/I590 intensity ratio. The fluorescence results were consistent with those drawn by XRD, where the high stability of YSZ:Eu coating was confirmed. Excellent thermal stability, in terms of both the phase structure and luminescence intensity, of YSZ:Eu coating indicates that the present preparation method is suitable for phosphor powder applications.

Microstructure and photoluminescence of Eu-doped Sr3Al2O6 phosphors calcined with and without H3BO3 flux

The development of highly efficient and stable red phosphors fabricated using cost-effective and simple mass-production methods is essential for applications in future displays and lighting devices. Herein, we investigate the phase formation, microstructures, and luminescence properties of Sr3Al2O6:Eu powders synthesized using a solid-state reaction process. Single-phase Sr3Al2O6:Eu phosphors exhibiting excellent photoluminescence with color-tunable orange-red and red colors under different excitation wavelengths were successfully synthesized. The optimal Eu doping concentration of Sr3Al2O6, yielding strong photoluminescence with phase stability, was 5 at. %, with the concentration quenching point determined by systematic exploration. The addition of H3BO3 as a flux significantly affected the grain size and improved the emission intensity of the synthesized (Sr0.95Eu0.05)3Al2O6 phosphors up to 12.5 wt %, while secondary phases were formed at higher flux concentrations. The photoluminescence intensities of the 5D0 → 7F1 and 5D0 → 7F2 transitions of 12.5 wt % H3BO3 added (Sr0.95Eu0.05)3Al2O6 increased by 3.4 and 4.2 times compared with the flux-free powders under the 394 nm-wavelength excitation, while the decay time decreased from 7.35 to 5.40 ms. Our report of the enhanced photoluminescence intensity and shortened decay time of (Sr0.95Eu0.05)3Al2O6 phosphors following the flux addition is promising for production of single-phase phosphors emitting multi-colors, which is needed for optical devices activated by various excitation frequencies.

Flexible Mechanoluminescent SrAl2O4:Eu Film with Tracking Performance of CFRP Fracture Phenomena.

Non-destructive testing of carbon-fiber-reinforced plastic (CFRP) laminates with bidirectional fiber bundles (twill-weave) using a mechanoluminescence (ML) technique was proposed. The dynamic strain distributions and fracture phenomena of the CFRP laminates in the tensile testing were evaluated by the fabricated ML sensor consisting of SrAl2O4:Eu (SAOE) powder and epoxy resin. The ML images for the ML sensor attached to the CFRP laminates with bidirectional fiber bundles gave a net-like ML intensity distribution similar to the original twill weave pattern. Specifically, it was found that the ML intensity on the longitudinal fiber bundle, which is the same as the tensile direction, is higher than that on the transverse fiber bundle. This indicates that the ML sensor can visualize the load share between fiber bundles in different directions of the CFRP laminate with high spatial resolution. Meanwhile, the ML sensor could also visualize the ultrafast discontinuous fracture process of the CFRP laminates and its stress distribution. The amount of SAOE powder in the ML sensor affects the tracking performance of the crack propagation. A higher SAOE amount leads to a fracture of the ML sensor itself, and a lower SAOE amount leads to poor ML characteristics.

Enhanced quantum efficiency of a self-organized silica mixed red phosphor CaAlSiN3:Eu

This study develops self-organized silica mixed CaAlSiN3:Eu (CASN) powder which improves light extraction efficiency (LEE) of the phosphor particles by enhanced scattering. A simple powder process conducted at room temperature, which is free from high temperature sintering process often applied for glass coated phosphors. Red phosphor CASN particles with a size of a few microns are mixed with nano-sized silica which was prepared in a tetraethyl orthosilicate (TEOS) solution of an alkali hydrolysis bath. The pair distribution function (PDF) profile obtained by an X-ray total scattering experiment indicates that the obtained nano-sized silica powders were amorphous. Compared to pure CASN powders, the composite CASN has an increased diffuse reflection, a reduced amount of absorption light, and an improved quantum efficiency (QE) of about 15%. QE is the product of internal quantum efficiency (IQE) and light extraction efficiency (LEE). The light emission lifetime measurement does not show a noticeable change between the pure and composite samples, indicating that the mixing process does not affect the electronic state of the Eu2+ luminescence center of CASN powder. That is, IQE of composite CASN is the same with that of pure CASN particles. Therefore, the improvement of QE of the composite CASN powders is due to the improvement of LEE.

Luminescence and energy transfer processes in LuNbO4:Bi, Eu

Microcrystalline powders of LuNbO4:Bi3+, Eu3+ with the same nominal Bi3+ concentration (2 at.%) and different nominal Eu3+ concentrations (varying from 0 to 8 at.%) are synthesized and analyzed by the X-ray diffraction method. Photoluminescence characteristics of the co-doped LuNbO4:Bi, Eu powders are investigated by the steady-state and time-resolved luminescence spectroscopy methods in a wide temperature range (4.2–500 K) and compared with those of the undoped and bismuth-doped LuNbO4. It is found that owing to the overlap of the intrinsic and Bi3+-related emission bands with the absorption bands of Eu3+, an effective non-radiative (resonance) energy transfer from both the host and the Bi3+-related exciton-like states to Eu3+ ions, resulting in the appearance of the luminescence in the 1.6–3.8 eV energy range, takes place in LuNbO4:Bi, Eu. The exchange interaction is found to be responsible for the energy transfer process. The possible application of LuNbO4:Bi, Eu in white light-emitting diodes is discussed.

Composite resin reinforced with fluorescent europium-doped hydroxyapatite nanowires for in-situ characterization

ObjectiveThe object is to find an easy but efficient way to illustrate the in-situ dispersion of nano-scaled one-dimensional fillers in composite resins, and to correlate their dispersion status with the properties of composite resins. MethodsFluorescent europium-doped hydroxyapatite nanowires (HANW:Eu) were synthesized via the hydrothermal method. The HANW:Eu was mixed into Bis-GMA/TEGDMA (60/40, w/w) at different contents (1–5wt.%), and different processing methods (kneading, grinding, stirring) were tested to achieve good dispersion of HANW:Eu with the aid of fluorescent imaging system. Then, the mixtures of HANW:Eu and barium glass powder (BaGP) were kneaded into resin at a fixed content (70wt.%) while at different mixing ratios. In addition to the 3D fluorescent imaging, characterizations were carried out on mechanical properties, fractured surface, wear resistance and polymerization shrinkage, to correlate the composite properties of with the dispersion status of the incorporated HANW:Eu. ResultsBy doping calcium with 5mol.% of europium, the obtained HANW:Eu displayed strong fluorescence, which made the illustration of its in-situ dispersion status within composites being possible. And this helped to judge that kneading was more efficient to homogeneously disperse HANW:Eu than grinding and stirring. However, it was illustrated vividly that HANW:Eu aggregated severely when it was co-incorporated with BaGP into composites at the total content of 70wt.%, which had not been previously revealed by other microscope observations. In comparison with composites containing 70wt.% of BaGP, improvements in the mechanical properties of resulting composites were identified for the cases containing 3wt.% of HANW and 67wt.% of BaGP, however, their wear volume loss and the polymerization shrinkage did not decrease as expected due to the HANW aggregations. SignificanceThe fluorescent filler prepared in this study provides a feasible strategy to illustrate the in-situ dispersion status of inorganic fillers, which provides guidance for the processing of composite resins.

Color tracing in the hydration process of α-Ca3(PO4)2:Eu

Eu-doped tricalcium phosphate (α-TCP:Eu) powders were obtained via solid-state reaction under air. The phase and microstructures of as-recieved samples and the hydration products soaked in 0.25 M K2HPO4 solution for different time was investigated using X-ray diffraction, SEM and Rietveld refinement method. The photoluminescence results of powders were changed with prolonged hydration time, not only the luminescence intensity of the products gradually depressed, but also the CIE chromaticity coordinates moved from bluish-green region of α-TCP phase to orange region of hydroxyapatite phase. The light emission change was confirmed by the color under the UV lamp. Therefore, results of this study suggested that the photoluminescence color of hydration products can be used as an obvious qualitative feature to trace the hydration process of α-TCP: Eu.

Low-temperature solid-state synthesis and luminescent performance of a novel Li2NaBP2O8-based phosphor activated with europium (III)

For the application of inorganic phosphors in solid-state lighting field, exploring a synthesis route with low energy consumption and low cost is the current research focus. In this study, a low-temperature solid-state synthesis route for a novel Li2NaBP2O8:Eu3+ (LNBP:Eu) phosphor is reported. The phase structure, morphology, and elemental composition of its powder phase are characterized. According to photoluminescence and X-ray photoelectron spectroscopy data, the occupancy site and oxidation state of doping europium are discussed. Under near-UV (395 nm) excitation, the powder phase exhibits reddish-orange emission with a dominant 5D0 → 7F1 transition of europium. The intensity of visible photoluminescence is closely influenced by the europium doping content. The optimal content is 0.04 mol, and concentration quenching is ascribed to energy transfer among the nearest-neighbor europium ions. Moreover, chromatic properties are investigated in detail. The obtained data show that the LNBP:Eu powder phase is a prospective phosphor for application in near-UV-converted warm white light-emitting diodes.

A new low-level tritiated water measurement system using CaF2(Eu) powders

With the development of ITER and CFETR, the measurement of tritium in low-level tritiated water is indispensable from the viewpoint of assessment and safety of tritium. To reduce radioactive waste produced by liquid scintillation counting, we have built a new low-level tritiated water measurement system using CaF2(Eu) powders. When an 8 mm thickness sample chamber and M sample (average grain sizes: 59.1 μm) were used, our measurement system responded accurately to tritium concentrations down to approximately 2.6 Bq/mL for 10 min measurements, and the calculated detection limit was about 4.6 Bq/mL. When a 3 mm thickness sample chamber and S sample (average grain sizes: 8.4 μm) were used, our measurement system responded accurately to tritium concentrations down to approximately 1.2 Bq/mL for 10 min measurements, and the calculated detection limit was about 0.64 Bq/mL.

The use of optical fibers as passageways for the scintillation light produced in CaF2 (Eu) powder in water for low-level tritiated water measurement

A solid scintillation counting (SSC) system which uses the mixture of CaF2(Eu) powder and tritiated water inside the chamber room will be developed for the measurement of low-level tritiated water. However, the coincidence detection efficiency and net count rate might be limited by the photon absorption in the chamber of the SSC detector. This paper discusses the feasibility of using light guide fibers as the optical passageway in the chamber room by Geant4 simulation. The simulation results show that the performance of the detector can be improved by using wavelength-shifting fibers as optical passageway in the chamber. The detector can maintain a 4.2% coincidence detection efficiency at a 6 cm chamber thickness, and the detection limit can be as low as 0.47 Bq/mL under 10 min measurement. As a result, using wavelength-shifting fibers as optical passageways in the chamber room of the SSC system is possible and effective.

Structural, microstructural, and luminescent properties of laser-sintered Eu-doped YAG ceramics

This work reports the laser sintering of Eu doped Y3Al5O12 (YAG:Eu) ceramics and their luminescent response as a function of Eu concentration. The laser sintering technique consists of using a CO2 laser to thermally activate the sintering process. The YAG:Eu powders were synthesized by a polymeric precursor method and yielded single cubic crystalline phase particles after calcination at 1000 °C for 2 h as determined by x-ray diffraction. The laser-sintered ceramics with a total sintering time of 7 min exhibited high relative density and homogeneous microstructure. The photoluminescent spectra of the YAG:Eu laser-sintered ceramics presented the well-know Eu3+ emissions along with two additional bands associated with Eu2+, as confirmed by XANES, even when sintered in air.

Effects of synthesis temperature on the microstructures and photoluminescent properties of Eu2O3-doped Sr2−xBaxSiO4 phosphors

In this study, Sr2−xBaxSiO4 (x = 0, 0.2, and 0.4) was used as the host material and Eu2O3 was used as the activator to produce commercial Sr2SiO4:Eu, Sr1.8Ba0.2SiO4:Eu, and Sr1.6Ba0.4SiO4:Eu phosphors by a solid-state reaction method. All the Sr2−xBaxSiO4–Eu phosphors were synthesized in the temperature range of 1000–1300 °C for 2 h. XRD patterns revealed that when different BaO contents and synthesis temperatures were used, all the Sr2−xBaxSiO4–Eu phosphors had similarly crystalline properties. The mainly crystalline phase changed from the (121) to the (103) plane as the BaO content changed from 0 to 0.2. In the case of all Sr2−xBaxSiO4–Eu powders, secondary or unknown phases were not observed if the synthesis temperature was lower than 1000 °C, and only the precursor SiO2 phase was observed in the 1000 °C-synthesized Sr2SiO4–Eu powder. This study also thoroughly investigated the effects of different BaO contents and synthesis temperatures on the photoluminescent properties of Sr2−xBaxSiO4–Eu phosphors. We show that the photoluminescent properties of Sr2−xBaxSiO4–Eu phosphors are dependent on the BaO content and synthesis temperature.

The substitutability of liquid scintillation cocktail for CaF2(Eu) powder in low-level tritiated water measurement

The liquid scintillation counting (LSC) is an established method for direct quantitative measurement of tritiated water, but the generated radiotoxic waste, its storage, handling and proper disposal is the major concern arising from using scintillation cocktail. In our work, CaF2(Eu) was chosen as the scintillation material to substitute scintillation cocktail in low-level tritiated water measurement. In order to find out the ideal vial type, grain size of powders and CaF2(Eu) powders quantity, three groups of 6 and 20 ml scintillation vials filled with different CaF2(Eu) powders were prepared. Using polyethylene vial, which is much smaller than the glass vial, significantly increased the detection efficiency. The highest detection efficiency was achieved by using polyethylene vial and 4 g S sample (average grain sizes: 8.355 μm). In addition, the polyethylene vials with 4 g S sample inside were most sensitive and had the best linear relation between tritium concentration and count rate. Under this condition, the detection limit can be as low as about 13 Bq/mL. The CaF2(Eu) powder can be re-used after a simple treatment. What's more, it is nontoxic as well as easy to store and disposal. These make it advantageous compared with traditional scintillation cocktail. With these results, the replacement of the scintillation cocktail with CaF2(Eu) powder in low-level tritiated water measurements is promising.

The effect of particle size of CaF2(Eu) powder and chamber thickness on solid scintillation counting for low-level tritiated water measurement

With the development of the International Thermonuclear Experimental Reactor (ITER) and the China Fusion Engineering Test Reactor (CFETR), the measurement of tritium in low-level tritiated water is indispensable from the viewpoint of assessment and safety of tritium. In our work, CaF2(Eu) was chosen as the scintillation material in the research to design a tritium monitor for tritiated water. The effect of particle size of CaF2(Eu) powder and chamber thickness on detection efficiency and count rate were assessed by Geant4 simulation. Our results show that reducing the CaF2(Eu) particle size can effectively improve the probability of energy deposition in the scintillator. Under the same conditions, the use of CaF2(Eu) particles with a radius of 0.5 μm increases the energy deposition probability by a factor of more than 20 compared to particles with a radius of 50 μm. However, the coincidence detection efficiency rapidly decreases as the chamber thickness of the solid scintillation counting (SSC) system increases when the particle size is small. With a fine CaF2(Eu) powder (particle radius of 1 μm), the coincidence detection efficiency is greater than 50% when the chamber thickness is 1 mm. Only approximately 35% of tritium decay is coincidentally detected when the chamber thickness is 5 mm. In addition, filling the chamber with CaF2(Eu) particles of different sizes leads to different maximum count rates. With the finest CaF2(Eu) powder, the SSC system has the highest count rate when the chamber thickness is 5 mm. With such results, the replacement of the scintillation cocktail with CaF2(Eu) powder in low-level tritiated water measurements is very promising. The simulation result will help in the design of a SSC system applied to low-level tritiated water measurement, and such a system will be tested in our future work.

Particle size effects on the dosimetry characteristics of K3Na(SO4)2:Eu TLD micro- and nanophosphors

K3Na(SO4)2:Eu is a highly sensitive TLD material in its microcrystalline form. It has been found that the material in its nanocrystalline form could also be used for very high dose measurements (of the order of 100 kGy) of high-energy radiations, like γ rays. However, it is not known whether the nanoparticle prepared by different methods of preparation, i.e., prepared using chemical coprecipitation method (by bottom up approach) and by ball milling (top down approach) behave in a similar manner. In the present paper, the TLD material was prepared by the standard solid state diffusion method, crushed and sieved/ball milled for different time periods to get particles of different sizes ranging from micro- to nanosize ranges. TL dosimetry characteristics of the material were studied and compared with our earlier results on the nanoparticles prepared by chemical coprecipitation method. It has been found that the K3Na(SO4)2:Eu powder sample in the particle size range 75–106 µm show the highest sensitivity and could be used up to 10 kGy dose of γ radiation. It has also been found that the nanoparticles prepared by two different approaches behave differently, i.e., the nanoparticles prepared by chemical coprecipitation method though are less sensitive than the microcrystalline but they do not saturate even up to very high doses (∼100 kGy, whereas the nanoparticles prepared by ball milling are equally sensitive to that of prepared by solution coprecipitation method but saturate early (at lower doses). It has been concluded that the surface defects might be playing an important role. The effect of high energy γ radiation on its repeated use as TLD phosphor for high doses (radiation hardening) was also studied and found that another TL peak at high temperature appears and its intensity varies on repeated use but the dosimetry peak remains invariant making the phosphor reusable for several times.

Effects of different dopants and synthesizing temperatures on the microstructures and photoluminescence properties of Sr1.4Ba0.6SiO4-based phosphors

Rare-earth ions can be used to design a virtually unlimited number of new luminescent materials because of their special energy level transitions in different energy bands. In this study, Nd2O3, Eu2O3 and Sm2O3 were used as dopants to produce commercial Sr1.4Ba0.6SiO4:Nd, Sr1.4Ba0.6SiO4:Eu, and Sr1.4Ba0.6SiO4:Sm phosphors by a solid-state reaction method. All the Sr1.4Ba0.6SiO4-based phosphors were synthesized in the temperature range of 1000–1300 °C for 2 h. XRD patterns revealed that when different dopants and synthesizing temperatures were used, the Sr1.4Ba0.6SiO4-based phosphors had different physical and luminescent properties. The SiO2 phase in Sr1.4Ba0.6SiO4:Nd powder was observed when the synthesizing temperature was 1000 °C but was absent if the synthesizing temperature was higher. There were no raw material or secondary phase residuals in the Sr1.4Ba0.6SiO4:Eu powder, even when the synthesizing temperature was 1000 °C. In the case of Sr1.4Ba0.6SiO4:Sm powder, secondary or unknown phases were still observed if the synthesizing temperature was lower than 1300 °C. When the temperature was increased from 1000 to 1300 °C, the 2θ value and the full width at half maximum value of the (103) plane underwent no apparent change in the Sr1.4Ba0.6SiO4:Nd and Sr1.4Ba0.6SiO4:Eu powders. This study also thoroughly investigated the effects of different dopants and synthesizing temperatures on the luminescent properties of Sr1.4Ba0.6SiO4-based phosphors.

Synthesis and characterization of flexible thermographic phosphor temperature sensors

The temperature dependence of the emission characteristics of thermographic phosphors has been used extensively for surface temperature measurements of systems where thermal management is critical for the safe operation of the system. The instantaneous, remote, and highly accurate nature of this form of temperature measurement makes it a very attractive measurement technique. However, the destructive nature of depositing phosphors directly onto the surface of interest and the complications of working with fine powders has limited the use of this technique in all areas. This work focuses on the design and characterization of polymer-encapsulated thermographic phosphor flexible sensors for surface temperature assessment. La2O2S:Eu powder was embedded in an elastomeric sleeve at concentrations of 10%, 25%, and 50% wt. and fully characterized. The effect of spin-coating on emission characteristics of La2O2S:Eu was tested and the decay times were compared to results obtained from bulk-doped samples previously created by the authors.

On the response of semitransparent nanoparticulated films of LuPO4:Eu in poly-energetic X-ray imaging applications

In the present work, we demonstrate the fabrication technique of highly translucent layers of nanoparticulated (~50 nm) LuPO4:Eu phosphor, present their basic luminescent properties and give results of their performance in a planar imaging system coupled to a CMOS photodetector. For comparison, the imaging performance of an opaque Gd2O2S:Eu phosphor screen prepared by sedimentation is also shown. The X-ray detection parameters as well as the luminescence efficiency of the investigated films were discussed. Results show that the in-line transmittance at ~600–700 nm, in the range of the phosphor luminescence, varies with respect to the thickness of the films from 40 to 50 % for a film of 67 μm thick to 4–12 % when the thickness increases to 460 μm. Yet, X-ray detection parameters get enhanced as the thickness of the films increases. Those results affect the luminescence efficiency curves of the films under poly-energetic X-ray radiation of various tube energies. The normalized noise power spectrum values were found similar for LuPO4:Eu films and a phosphor screen made using commercial Gd2O2S:Eu powder. The detective quantum efficiency of our films is clearly lower compared to the Gd2O2S:Eu screen from 2 to 10 cycles mm−1 frequency range while the modulation transfer function is lower from 0 to 5.5 cycles mm−1 frequency range. The acquired data allow to predict that high-temperature sintering of our films under pressure may help to improve their imaging quality, since such a processing should increase the luminescence efficiency without significant growth of the grains and thus without sacrificing their translucent character.