Electrophoretic deposition is employed to deposit flower-like TiO2 (F-TiO2) particles onto stainless steel textiles to obtain a Fe@F-TiO2/PDMS hybrid textile as the negative tribo-material. The electrophoresis process enables adjustable deposit amounts and three-dimensional and uniform deposits of flower TiO2. The textile triboelectric nanogenerators (tTENGs) fabricated from the Fe@F-TiO2/PDMS hybrid textile working in conjunction with cotton and silk exhibit excellent performances. The tTENG generates a voltage of 120 V, a current of 25 mu A and an output power of 0.85 W m(-2) with the cotton and 110 V, 30 mu A and 1.05 W m(-2) with the silk. The flower-like TiO2 is significant for the high performance of the tTENG, being attributed to the tailored surface and improved permittivity. Wearable tTENGs exhibit good durability after 8,000 cycles and power 58 light emitting diodes. By utilizing the worn tTENG, real-time biomechanical energy harvesting is realized; furthermore, a wireless communication via infrared rays is achieved, confirmed by the successfully receiving of the wireless signal and lighting up of the indicator LED. This work demonstrates high-performance hybrid textiles prepared by electrophoretic deposition and tTENGs for applications in wearable real-time energy harvesters and wireless communication units.

In this study, a flower-like TiO2 filled polymethyl methacrylate (PMMA) composite is presented as a positive tribo-material to produce an excellent-performance triboelectric nanogenerator (TENG). By working in conjunction with polydimethylsiloxane (PDMS), the flat-surface PDMS/PMMA-flower TiO2 TENG generates a voltage of 1200 V, a current of 139 mA m-2 and an output power of 34.85 W m-2, showing significant enhancement compared with its counterpart utilizing neat PMMA as the positive tribo-material under the same operating conditions, whose voltage is 620 V, current is 78 mA m-2 and output power is 13.89 W m-2, respectively. The performance of the TENG is highly dependent on filler loadings of TiO2 flower particles in PMMA composites with an optimal filler loading of 40 wt% with the highest performances. The flower TiO2 is vital to the enhanced performances of the TENG, which is due to the modified surface, the tailored dielectric constant and the space charge polarization. The TENG is capable of powering 600 light emitting diodes, a calculator and a digit display, and applied in self-powered electrophoretic deposition of oxide films. This work demonstrates a facile, low-cost approach for obtaining high-performance TENGs utilizing a PMMA-flower TiO2 composite as the positive tribo-material for applications in sustainable power systems.

Cerium-doped YAlO3:Ce (YAP:Ce) is an interesting oxide scintillator that exhibits a wider range of light yield nonproportionality on a sample-to-sample basis than most other well-known oxide scintillators. In general, most oxide materials, such as Bi4Ge3O12 and Lu2SiO5:Ce, are thought to have an intrinsic proportional response that is nearly constant between samples and independent of growth conditions. Since light yield nonproportionality is responsible for degrading the achievable energy resolution of all known scintillators, it is important to understand what contributes to the behavior. In an attempt to understand if the phenomenon can be affected by growth parameters or by other means, seven samples of YAP:Ce were collected from various sources, and eight samples were grown in-house using the Czochralski method. Based on optical and scintillation measurement as well as direct measurement of the cerium concentration, it was determined that the light yield proportionality in YAP:Ce is strongly related to the cerium concentration. Samples that were found to have higher relative cerium concentration displayed a more proportional light yield response. In addition, it was determined that samples with higher cerium concentration also exhibit a faster decay time and an enhanced energy resolution when compared to samples with less cerium. It was also determined that growth in a reducing atmosphere can effectively suppress a parasitic optical absorption band.

Block detector designs, utilizing a pixelated scintillator array coupled to a photosensor array in a light-sharing design, are commonly used for positron emission tomography (PET) imaging applications. In practice, the spatial sampling of these designs is limited by the crystal pitch, which must be large enough for individual crystals to be resolved in the detector flood image. Replacing the conventional 2D scintillator array with an array of phoswich elements, each consisting of an optically coupled side-by-side scintillator pair, may improve spatial sampling in one direction of the array without requiring resolving smaller crystal elements. To test the feasibility of this design, a 4×4 phoswich array was constructed, with each phoswich element consisting of two optically coupled, 3.17×1.58×10mm3 LSO crystals co-doped with cerium and calcium. The amount of calcium doping was varied to create a ‘fast’ LSO crystal with decay time of 32.9 ns and a ‘slow’ LSO crystal with decay time of 41.2 ns. Using a Hamamatsu R8900U-00-C12 position-sensitive photomultiplier tube (PS-PMT) and a CAEN V1720 250 MS/s waveform digitizer, we were able to show effective discrimination of the fast and slow LSO crystals in the phoswich array. Although a side-by-side phoswich array is feasible, reflections at the crystal boundary due to a mismatch between the refractive index of the optical adhesive (n=1.5) and LSO (n=1.82) caused it to behave optically as an 8×4 array rather than a 4×4 array. Direct coupling of each phoswich element to individual photodetector elements may be necessary with the current phoswich array design. Alternatively, in order to implement this phoswich design with a conventional light sharing PET block detector, a high refractive index optical adhesive is necessary to closely match the refractive index of LSO.

Hg3Se2Br2 is a wide band gap semiconductor (2.22 eV) with high density (7.598 g/cm(3)) and crystallizes in the monoclinic space group C2/m with cell parameters of a = 17.496 (4) angstrom b = 9.3991 (19) angstrom c = 9.776(2) angstrom, beta = 90:46(3)degrees, V = 1607.6(6) angstrom(3). It melts congruently at a low temperature, 566 degrees C, which allows for an easy single crystal growth directly from the stoichiometric melt. Single crystals of Hg3Se2Br2 up to 1 cm long have been grown using the Bridgman method. Hg3Se2Br2 single crystals exhibit a strong photocurrent response when, exposed to Ag X-ray and blue diode laser. The resistivity of Hg3Se2Br2 measured by the two probe method is on the order of 10(11) Omega.cm, and the mobility lifetime product (mu tau) of the electron and hole carriers estimated from the energy spectroscopy under Ag X-ray radiation are (mu tau)(e) approximate to 1.4 x 10(-4) cm(2)/V and (mu tau)(h) approximate to 9.2 x 10(-5) cm(2)/V. Electronic structure calculations at the density functional theory level indicate a direct band gap and-a relatively small effective mass for carriers. On the basis of the photoconductivity and hard X-ray spectrum, Hg3Se2Br2 is a promising candidate for X-ray and gamma-ray radiation detection at room temperature.

The refined synthesis and optimized crystal growth of high quality Pb2P2Se6 single crystals are reported. Improved experimental procedures were implemented to reduce the oxygen contamination and improve the stoichiometry of the single crystal samples. The impact of oxygen contamination and the nature of the stoichiometry deviation in the Pb2P2Se6 system were studied by first-principles density functional theory (DFT) electronic structure calculations as well as experimental methods. The DFT calculations indicated that the presence of interstitial oxygen atoms (O-int) leads to the formation of a deep level located near the middle of the gap, as well as a shallow acceptor level near the valence band maximum. In addition, total energy calculations of the heat of formation of Pb2P2Se6 suggest that the region of thermodynamic stability is sufficiently wide. By refining the preparative procedures, high quality Pb2P2Se6 single crystal samples were reproducibly obtained. These Pb2P2Se6 single crystals exhibited excellent optical transparency, electrical resistivity in the range of 10(11) Omega.cm, and a significant increase in photoconductivity. Infrared photoluminescence of the Pb2P2Se6 single crystals was observed over the temperature range of 15-75 K. Detectors fabricated from boules yielded a clear spectroscopic response to both Ag K alpha X-ray and Co-57 gamma-ray radiation. The electron and hole mobility lifetime product (mu tau) of the current Pb2P2Se6 detectors were estimated to be 3.1 x 10(-4) and 4.8 X 10(-5) cm(2)/V, respectively.

Scintillation materials that lack intrinsic luminescence centers must be doped with optically active ions in order to provide luminescent centers that radiatively de-excite as the final step of the scintillation process.Codoping, on the other hand, can be defined as the incorporation of additional specific impurity species usually for the purpose of modifying the scintillation properties, mechanical properties, or the crystal growth behavior.In recent years codoping has become an increasingly popular approach for engineering scintillators with optimal performance for targeted applications.This report reviews several successful examples and its effect on specific properties.

CsPbBr3 has direct band gap (orange color, 2.25 eV), high density (4.85 g/cm3), attenuation coefficient comparable to CZT, and high resistivity ~10^9 ohm∙cm. These fundamental physical properties of CsPbBr3well meet the requirements for gamma-ray detector materials. CsPbBr3 exhibits the carrier mobility-lifetime product in the order of 10^-4 cm2/V promising enough to be further developed for practical applications. The major challenge in the process to further enhance the detection performance is the carrier traps present at a deep level of the energy gap which should be minimized. We report the synthesis, purification, crystal growth and physical characterization of the CsPbBr3 crystals obtained by new processes we developed for highly pure materials with reduced carrier traps. The starting binary materials were prepared by reaction of Cs2CO3/HBr and Pb(ac)2/HBr in aqueous solution. Purification of materials was performed by sublimation, bromination with HBr gas, and filtration of molten materials. Large single crystals were grown by the vertical Bridgman and EelectroDynamic Gradient method and cut to the dimensions appropriate for assessment of the material for gamma-ray detector applications. All characterization including optical characteristics, charge transport properties, photoconductivity, and gamma-ray spectroscopy from the new single crystals of CsPbBr3 will be presented. In addition, the charge carrier traps profile has been studied for this compound by Deep-Level Transient Spectroscopy (DLTS), Thermally Stimulated Luminescence (TSL), and Photoluminescence (PL) and will be presented.

Single crystals of Gd3Ga3Al2O12:Ce with Ca, B and Ba codopants were successfully grown using the Czochralski technique. The samples of each composition were irradiated to 10 kGy and 100 kGy gamma dose to determine the radiation induced absorption. The Ca co-doped crystal was found to have maximum induced absorption, while B and Ba co-doped were found to be more radiation hard. The reduction in transmission could be partially restored at room temperature without any annealing treatment of the crystals. The additional absorption was also measured after annealing the crystals in reducing environment and compared with the radiation induced absorption. Thermoluminescence measurements were carried out to explain the defect structure and recovery of the transmission reduction at room temperature.

GGAG:Ce crystals with various Ca concentrations were grown by the Czochralski technique. The introduction of Ca2+ ions into a trivalent site results in a change in the Ce valence state as well as an additional F+ luminescence center. The changes of Ce valence state could be affected by various annealing atmospheres and were investigated via measuring the Ce3+ absorbance and observing the color change of the sample. Photoluminescence spectra and photoluminescence decay were used to reveal the occurrence of F+ center related to the oxygen vacancies during the annealing. A redox mechanism and a charge compensation process are proposed to explain the change in Ce state charge and F+ center during the annealing.

Multicomponent garnet materials can be made in optical ceramic as well as single crystal form due to their cubic crystal structure. In this work, high-quality Gd3Ga3Al2O12:0.2at% Ce (GGAG:Ce) single crystal and (Gd,Lu)3Ga3Al2O12:1at% Ce (GLuGAG:Ce) optical ceramics were fabricated by the Czochralski method and a combination of hot isostatic pressing (HIPing) and annealing treatment, respectively. Under optical and X-ray excitation, the GLuGAG:Ce optical ceramic exhibits a broad Ce3+ transition emission centered at 550nm, while the emission peak of the GGAG:Ce single crystal is centered at 540nm. A self-absorption effect in GLuGAG:Ce optical ceramic results in this red-shift of the Ce3+ emission peak compared to that in the GGAG:Ce single crystal. The light yield under 662keV γ-ray excitation was 45,000±2500 photons/MeV and 48,200±2410 photons/MeV for the GGAG:Ce single crystal and GLuGAG:Ce optical ceramic, respectively. An energy resolution of 7.1% for 662keV γ-rays was achieved in the GLuGAG:Ce optical ceramic with a Hamamatsu R6231 PMT, which is superior to the value of 7.6% for a GGAG:Ce single crystal. Scintillation decay time measurements under 137Cs irradiation show two exponential decay components of 58ns (47%) and 504ns (53%) for the GGAG:Ce single crystal, and 84ns (76%) and 148ns (24%) for the GLuGAG:Ce optical ceramic. The afterglow level after X-ray cutoff in the GLuGAG:Ce optical ceramic is at least one order of magnitude lower than in the GGAG:Ce single crystal.

Polycrystalline Gd3Ga3Al2O12:Ce (GGAG:Ce) pellets with various codopants were prepared via solid-state synthesis and characterized by X-ray diffraction, radioluminescence (RL), photoluminescence (PL), reflectivity and PL decay measurements. GGAG:Ce pellets codoped with B and Ba were found to have higher RL intensity than pellets with other codopants, while Ca codoping improved the decay time but reduced the RL intensity. These results were strongly correlated with the performance of these codopants in GGAG:Ce single crystals. The light yield of the single crystals codoped with B or Ba was similar to 15% higher than the light yield of the GGAG:Ce crystal without codoping, while Ca codoping in single crystals resulted in lower light yield but shorter scintillation decay time (43 ns vs. 56 ns). The consistent performance of these codopants in both matrix forms indicates that sintering pellets may be used as a simple cost effective technique to evaluate compositions for likely single crystal scintillator performance. (C) 2014 Elsevier B.V. All rights reserved.

Polycrystalline Gd3Ga3Al2O12:Ce (GGAG:Ce) pellets with various codopants were prepared via solidstate synthesis and characterized by X-ray diffraction, radioluminescence (RL), photoluminescence (PL), reflectivity and PL decay measurements. GGAG:Ce pellets codoped with B and Ba were found to have higher RL intensity than pellets with other codopants, while Ca codoping improved the decay time but reduced the RL intensity. These results were strongly correlated with the performance of these codopants in GGAG:Ce single crystals. The light yield of the single crystals codoped with B or Ba was ~ 15% higher than the light yield of the GGAG:Ce crystal without codoping, while Ca codoping in single crystals resulted in lower light yield but shorter scintillation decay time (43 ns vs. 56 ns). The consistent performance of these codopants in

Indium doped cesium iodide (CsI:In) single crystals were grown by the Bridgman method. A comparison study of the scintillation properties of our CsI: In and commercially available CsI:Tl single crystals was carried out, including scintillation decay time, energy resolution, non-proportionality, absolute light yield, and afterglow. Under X-ray excitation, the CsI: In emission corresponds to a symmetrical broad band centered at 545 nm. Its scintillation decay time is 1.99 +/- 0.02 mu s at room temperature under Cs-137 gamma-ray excitation. The CsI: In light yield was found to be 34, 700 +/- 1735 photons per MeV with an energy resolution of 9.1 +/- 0.3%, based on the pulse height spectra under Cs-137 excitation. The afterglow level of CsI:In over 130 ms after pulsed X-ray excitation was two orders of magnitude higher than that of CsI:Tl.

A textured CoFe2O4 ceramic was fabricated by reactive template grain growth (RTGG) method using rodlike alpha-FeOOH particles as templates. The template particles were synthesized by hydrothermal method, the particles showed good crystallization and rod-like shape with a diameter of 0.1-0.2 mu m and an aspect ratio of 20-50. (110) oriented CoFe2O4 ceramic was obtained after a sintering process. The ceramic sintered at 1150 degrees C for 4 h showed dense and oriented structure with orientation degree of 0.89. Different magnetic hysteresis loops were observed along the in-plane and out-of-plane direction of the textured CoFe2O4, which was due to anisotropy properties of the sample. The textured ceramic exhibited an in-plane M-s enhancement (355 emu/cm(3)) compared to that of the non-textured ceramics (320 emu/cm(3)) in the same sintering conditions. (C) 2015 Elsevier B.V. All rights reserved.

Single crystals of Gd 3 Ga 3 Al 2 O 12 :Ce with Ca, B and Ba codopants were successfully grown using the Czochralski technique. The samples of each composition were irradiated to 10 kGy and 100 kGy gamma dose to determine the radiation induced absorption. The Ca co-doped crystal was found to have maximum induced absorption, while B and Ba co-doped were found to be more radiation hard. The reduction in transmission could be partially restored at room temperature without any annealing treatment of the crystals. The additional absorption was also measured after annealing the crystals in reducing environment and compared with the radiation induced absorption. Thermoluminescence measurements were carried out to explain the defect structure and recovery of the transmission reduction at room temperature.

Codoping is a method of current interest for modifying the properties of scintillators. The study reported here explores the effect of codoping on cerium doped Gd3Ga3Al2O12 (GGAG:Ce) crystals with various concentrations of Ca. These single crystals were grown via the Czochralski technique with Ce concentrations fixed at 0.2at% and Ca concentrations ranging from 0.1at% to 0.4at% in the initial melt. The relationship between dopant concentration and light yield, rise time, and scintillation and photoluminescence decay times was determined. In addition, the absorbance, photoluminescence, radioluminescence, afterglow and thermoluminescence dependence on the dopant concentration are presented. In some of the Ca codoped crystals, an additional luminescence center was observed with an excitation wavelength of 350nm and an emission wavelength of 400nm and a photoluminescence decay time of ~3.5ns.

It is difficult to obtain the pure YAP phase in YAP:Ce pellets synthesized by solid-state reaction at high temperature (up to 1500°C), because a small amount of YAG (Y 3 Al 5 O 12 ):Ce tends to form, resulting in additional emission and degrading the scintillation performance. We attempted three methods to suppress the formation of this YAG phase: a) codoping with Ca, B and Ba, b) adding Ba and F compounds as flux, and c) adding excess Y. The presence or absence of a YAG phase in the YAP pellets was determined by photoluminescence (PL), radioluminescence (RL) and reflectivity spectra. The most significant suppression of the YAG phase was achieved by adding 10% excess Y, after which the YAG emission peak was nearly completely suppressed in the RL and PL spectra, and no YAG phase absorbance was found in reflectivity spectra compared to stoichiometric YAP pellets.

Codoping is a method of current interest for modifying the properties of scintillators. The study reported here explores the effect of codoping on cerium doped Gd3Ga3Al2O12 (GGAG:Ce) crystals with various concentrations of Ca. These single crystals were grown via the Czochralski technique with Ce concentrations fixed at 0.2 at% and Ca concentrations ranging from 0.1 at% to 0.4 at% in the initial melt. The relationship between dopant concentration and light yield and scintillation decay times was determined.