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The SrWO4:RE3+ (RE = Eu, Sm, Pr) fluorescent powders are synthesized using a high-temperature solid-state method. The phase structures and morphologies of the fluorescent powders are examined using X-ray diffraction and field-emission scanning electron microscopy, respectively. The results reveal that pure phase SrWO4 can be prepared via calcination at 900oC for 4 h and that doping with rare-earth ions has no effect on the crystal phase of the fluorescent powders; SrWO4 powders doped with three rare-earth ions all form spherical-like structures. The luminescence properties of the samples are evaluated using a fluorescence spectrometer, and the excitation and emission spectra of the SrWO4:RE3+ (RE = Eu, Sm, Pr) fluorescent powders are analyzed. The results indicate that SrWO4:Eu3+ fluorescent powder can be effectively excited by ultraviolet light at 395 nm and emit red light at 615 nm when a doping concentration of Eu3+ is 7%; Sm3+- and Pr3+-doped SrWO4 can emit red light at 650 and 687 nm when excited at 406 and 460 nm, respectively, with a doping concentration of 5% each. A W-LED device with SrWO4:Eu3+ pink fluorescent powder and a 395-nm UV chip is successfully assembled. The chromaticity coordinates of the device are (0.3055, 0.3532), exhibiting prominent white light. SrWO4:RE3+ (RE = Eu, Sm, Pr) fluorescent powders are expected to be red suorescent powders for UV-excited white LEDs. [ABSTRACT FROM AUTHOR]

It has been a research hot spot how to efficiently heighten the photocatalytic activity and stability of CdS-based photocatalysts for H 2 evolution. Here, SrWO 4 /CdS nanoparticles which contained CdS/SrWO 4 heterojunctions were prepared. Meanwhile, their photocatalytic performance and stability were investigated in detail for H 2 evolution. At last, the photocatalytic mechanism of the SrWO 4 /CdS nanoparticles was discussed roughly. The results show that the photocatalytic performance of CdS can be heightened significantly due to introduction of SrWO 4. The fastest evolution rate of H 2 over the SrWO 4 /CdS nanoparticles is 392.5 μmol g−1 h−1, which is 5.8 times as high as that over the pure CdS nanomaterial. More interestingly, the SrWO 4 /CdS nanoparticles possess excellent stability. The evolution rate of H 2 over the photocatalyst used 10 times can be up to 473 μmol g−1 h−1, which is the same as that over the once used sample, even is 37% higher than that over of the fresh one. In contrast, after used five times, the photocatalytic activity of the pure CdS nanomaterial is only 57% of that of the fresh sample. This study will supply a new idea for the design and development of highly stable and efficient CdS-based photocatalysts for H 2 evolution in the future. [Display omitted] • Novel pathway to boosting stability of the CdS-based photocatalyst. • Simultaneously heighten stability and activity of the CdS-based photocatalyst. • Stable and efficient photocatalyst containing CdS and SrWO 4 for H 2 evolution. [ABSTRACT FROM AUTHOR]

In this study, we successfully synthesized rare-earth-doped crystalline SrWO4 at room temperature by co-precipitation. The results from the X-ray diffraction analysis showed a main diffraction peak related to the (112) plane. Phosphors doped with either Dy3+ or Sm3+ ions showed strong light absorption in the UV region and blue-yellow and red light emission. To synthesize a white light phosphor, Dy3+ and Sm3+ ions were co-doped to produce a SrWO4:[Sm3+]/[Dy3+] phosphor. When the Sm3+ ion concentration was increased and the Dy3+ concentration was maintained, the red light intensity increased while the blue-yellow light intensity decreased. The composites were combined with polydimethylsiloxane (PDMS), and a flexible composite material was fabricated. The composite exhibited various luminescence properties under UV and visible light, which suggested its potential for use as an LED color filter. [ABSTRACT FROM AUTHOR]

Crystalline SrWO4 was synthesized at room temperature using a co-precipitation method. To use the SrWO4 as a phosphor, green and red phosphors were synthesized by doping with Tb3+ and Eu3+ rare earth ions. The synthesized samples had a tetragonal structure, and the main peak (112) phase was clearly observed. When the sample was excited using the absorption peak observed in the ultraviolet region, SrWO4:Tb3+ showed an emission spectrum of 544 nm, and SrWO4:Eu3+ showed an emission spectrum of 614 nm. When Tb3+ and Eu3+ ions were co-doped to realize various colors, a yellow-emitting phosphor was realized as the doping concentration of Eu3+ ions increased. When the synthesized phosphor was scattered on a glass substrate with fingerprints, as used in the field of fingerprint recognition, the fingerprint was revealed by green, red, and yellow emissions in response to a UV lamp. [ABSTRACT FROM AUTHOR]

A simple co-presipitation method has been developed to synthesize SrWO4 and Ag°-SrWO4 micro/nanostructures with different morphologies, including platelet-, star- and flower-like, in the presence of Na(B(C6H5)) as surfactant. The formation of platelet-, star- and flower-like shapes of particulate system was examined by electron microscopy technique. The products were characterized by X-ray diffraction, scanning electron microscope, UV-vis absorption, energy dispersive X-ray and fourier transform infrared spectra. The scheelite type tetragonal structure of all the synthesized compounds was revealed by powder X-ray diffraction analysis. The influence of surfactant concentration (sodium tetraphenylborate as new surfactant) on the size and morphology of products was investigated. Finally, a good photocatalytic activity was first discovered of the Ag°-SrWO4 microcrystals for the degradation of methyl orange dye after 100 min under UV-vis light. Hence, from the present investigation it was observed that the doping of Ag in SrWO4 will yield a new kind of multifunctional material for fabricating electronic devices.

To improve the luminous performance of SrWO4; Dy3+, Eu3+ phosphors, the Li十 and Al$+ with valence state compensation and smaller radius were used as dopant. The white LED phosphor with low color temperature and good luminous intensity was prepared in this study. The phase structure - morphology and luminescence properties of the samples were characterized by the X ray Diffraction (XRD) - Scanning Electron Microscope(SEM), and Spectrophotometer. The results showed that the main phase of the sample doped with metal ions was SrWCX, and the microstructure was mainly a spindle structure. The luminous intensity and luminous color have been greatly improved for the sample doped with 7.5% A1 什 compared with non doped phosphors. The color coordinate was(0. 338,0, 342), the color temperature was 4 337 K, and the luminescence intensity at 619 nm was 8 times higher than that of samples without metal ions. For the sample(SrWO4 5 2. 5%Dy+, 7. 5%Eu+, 7. 5%Li+), the color coordinate was (0. 380, 0, 401), the color temperature was 4 867 K, and the luminescence intensity at 619 nm was 5 times higher than that of samples without metal ions. The energy transfer effect between luminescent ions can be improved by adding Li+ and Al$+, then the red component of the phosphor was increased, resulting in the red shift of the color coordinate and decreased color temperature* This study is meaningful in the field of low color temperature lighting. [ABSTRACT FROM AUTHOR]

Rapid-monitoring of drugs has attracted tremendous consideration owing to robust global demand for cost-effective and high effectiveness. Binary metal oxides with various morphology have been reported as electrodes for electrochemical sensor to fulfilling the clinical and enviromental requirements. In this study, strontium tungstate (SrWO4) nanoflakes have been successfully prepared via the facile sonochemical method for the first time. The characteristics of as-prepared SrWO4 are systematically measured by various analytical and spectroscopic methods. The SrWO4 nanoflakes are utilized to modify the electrochemical electrode for the sulfadiazine (SDZ) determination. The SrWO4 modified electrode possesses excellent electrocatalytic activity and high recognition capability for the electrochemical detection of SDZ. Impressively, the as-fabricated SrWO4 modified electrode attainted lowest oxidation peak at +0.93 V (vs Ag/AgCl2) with the limit of detection of 0.009 μM, the sensitivity of 0.123 µA µM−1 cm2 and linear detection range of 0.05–235 μM. The enhanced performance of proposed SrWO4-based sensors could be attributed to the catalytic effect, large surface area, good electrical conductivity and physicochemical nature. Notably, the electrocatalytic performances of the SDZ sensors are good as compared to the previous literature, indicating the significance of the newly designed SrWO4 modified electrode. The real-sample diagnosis by the SDZ detection in environmental sample demonstrates the proposed SrWO4-based sensors with good recovery range.

Crystalline SrWO4 was synthesized at room temperature using a co-precipitation method. To use the SrWO4 as a phosphor, green and red phosphors were synthesized by doping with Tb3+ and Eu3+ rare earth ions. The synthesized samples had a tetragonal structure, and the main peak (112) phase was clearly observed. When the sample was excited using the absorption peak observed in the ultraviolet region, SrWO4:Tb3+ showed an emission spectrum of 544 nm, and SrWO4:Eu3+ showed an emission spectrum of 614 nm. When Tb3+ and Eu3+ ions were co-doped to realize various colors, a yellow-emitting phosphor was realized as the doping concentration of Eu3+ ions increased. When the synthesized phosphor was scattered on a glass substrate with fingerprints, as used in the field of fingerprint recognition, the fingerprint was revealed by green, red, and yellow emissions in response to a UV lamp.

Scheelite-type strontium tungstate (SrWO4) phosphor powders were successfully synthesized using strontium nitrate and tungstic acid as starting materials by a gamma-ray irradiation-assisted polyacrylamide gel route. The phase purity, structure, functional groups, surface morphology, chemical composition, colorimetric, optical and photoluminescence properties of SrWO4 phosphor powders were systematically studied by various testing instruments. The crystallite size of SrWO4 phosphor powders increases with the increasing of sintering temperature. The color, optical and photoluminescence properties of SrWO4 phosphor powders are strongly dependent on the sintering temperature, carbon chain and the distortion of tetrahedral [WO4] clusters. The fluorescence emission at (310Â nm, 338Â nm, 360Â nm and 400Â nm) and 465Â nm can be ascribed to the new energy level formed by a carbon chain, amorphous SrWO4 or oxygen vacancy, and the distortion of tetrahedral [WO4] clusters, respectively. [ABSTRACT FROM AUTHOR]

In this paper, we present a systematic investigation of the photocatalytic H2 production over the Sr1−1.5xLaxWO4 (0 ≤ x ≤ 0.2) solid solutions. The doped La3+ ion in the crystal structure was identified by the Le Bail fit on the X-ray diffraction pattern of the as-prepared sample. The cell volume of the doped sample was linearly decreased by the augmentation of the La3+ ion. The morphology and composition of Sr0.82La0.12WO4 were observed by the transmission electron microscope, scanning electron microscope, and X-ray photoelectron spectroscopy. And then the loading of Cu, Ag, Au, Pt, Ni, and Ru as cocatalysts on sub-crystallite Sr0.82La0.12WO4 sample for H2 production was studied. The optimum H2 production rate is 309.7 μmol/h/g for 1.5 wt% Ru/Sr0.82La0.12WO4, which is 3.1 times than the undoped sample. And its apparent quantum yield is 0.44% at 365 (± 15) nm. All the photocatalysts recycled after the photocatalytic reactions show no degradation. [ABSTRACT FROM AUTHOR]

Ammonia synthesized by nitrogen reduction is the most promising new energy material. Photoelectrocatalytic (PEC) nitrogen reduction reaction (NRR) occurs under ambient conditions and is the optimal alternative to the energy-intensive Haber-Bosch method. Here, we report the one-step reaction synthesis of Ti–WO 3 /SrWO 4 as a photocathode for ammonia synthesis. First-principles calculations demonstrate that Ti doping can afford nitrogen-adsorption sites, and Ti3+ undergoes chemical adsorption and becomes a nitrogen-activation site by providing electrons to nitrogen. Under light irradiation, the photogenerated electrons are captured by Ti4+; this is conducive to the activation and regeneration of Ti3+, thus forming a nitrogen fixation cycle and improving the nitrogen fixation yield. At − 0.5 V vs. RHE, the ammonia synthesis efficiency reaches 11.17 μg h-1 cm-2, which is four times that of SrWO 4. Furthermore, the high stability and N-gas sensitivity of Ti–WO 3 /SrWO 4 in the NRR indicate that it can be used as an efficient and stable photoelectrocatalyst for ammonia synthesis. [Display omitted] • SrWO 4 firstly utilized as an effective photoelectrocatalyst for N 2 fixation. • Ti-WO 3 /SrWO 4 was synthesized by a one-step reaction based on H 2 WO 4. • N 2 is more easily adsorbed on Ti to facilitate the NRR reaction. • Ti-WO 3 /SrWO 4 PEC synthesis of ammonia is greatly improved. [ABSTRACT FROM AUTHOR]

[Display omitted] • Using SrWO 4 to enhance photocatalytic activity of Cd 0.5 Zn 0.5 S. • The fastest H 2 production rate of 9.47 mmol g−1 h−1 is achieved. • The photocatalytic activity of Cd 0.5 Zn 0.5 S is enhanced 31-fold. It has been attracting worldwide interests in efficient and sustainable H 2 generation. Developing an efficient photocatalyst is the major kernel to achieve the aforesaid goal. Here, we developed a visible photocatalytic system using Cd 0.5 Zn 0.5 S and SrWO 4. And then its photocatalytic behavior was explored for H 2 generation under visible light illumination. We found that the obtained Cd 0.5 Zn 0.5 S/SrWO 4 nanocomposite was a visible photocatalyst with outstanding photocatalytic performance for H 2 production. When it was used as a photocatalyst, the fastest H 2 production rate of 9.47 mmol g−1 h−1 would be achieved. Moreover, the results also indicate that SrWO 4 is an excellent cocatalyst for Cd 0.5 Zn 0.5 S. The photocatalytic performance of Cd 0.5 Zn 0.5 S will be strengthened by about 31 times due to usage of SrWO 4. These research results would provide helpful insight into the design and preparation of visible photocatalysts with excellent performance used for H 2 generation tomorrow. [ABSTRACT FROM AUTHOR]

A series of Pr3+ doped SrWO 4 phosphors were synthesized using solid-state reaction routes. The phase composition, photoluminescence and temperature sensitivities of as-prepared materials were investigated. Rietveld refinement of measured XRD data was applied to analyze the lattice parameters. The optical transition was elaborated using UV–visible diffuse reflectance spectra and photoluminescence spectra. The photoluminescence measurements confirmed the strong visible light emission from the developed phosphors under both UV excitation at 250 nm and blue excitation at 450 nm. Notably, the maximum emission intensity was observed at a Pr3+ doping concentration of 2 mol%. Furthermore, the fluorescence intensity ratio (FIR) technique was employed, focusing on the emissions originating from the 3P 0 and 1D 2 state of Pr3+ within the temperature range of 298–598 K. Two FIR groups were adopted in this case, which can verify each other to achieve self-calibration. Typically, SrWO 4 :0.02Pr3+ exhibited remarkable performance as a temperature sensor, displaying an absolute sensitivity (Sa) of 3.11%K−1 and a relative sensitivity (Sr) of 0.81%K−1. As a result, the significant temperature-dependent PL and remarkable down-conversion luminescence make the SrWO 4 :Pr3+ material a promising candidate for optical thermometers and UV to visible converters of solar cell applications. • Intense visible emission of SrWO 4 :Pr3+ excited by 250 nm and 450 nm was observed. • FIR from non-thermally coupled energy levels was used for temperature sensing. • The wide-range and highly-sensitive of optical temperature sensing were realized. • The self-calibration of temperature measurement was achieved by two FIR groups. [ABSTRACT FROM AUTHOR]

• An intracavity SrWO 4 Raman laser at 2637.5 nm is first investigated. • The maximum average output power of 720 mW is achieved. • The maximum pulse energy and peak power are 196 μJ and 10.9 kW, respectively. • The Raman laser beam is close to fundamental transverse electromagnetic mode. We first report a 2.6 µm mid-infrared SrWO 4 Raman laser, intracavity-pumped by an actively Q-switched Ho:YAG laser. The 2122 nm fundamental laser was generated from the Ho:YAG laser, which was resonantly pumped by a 1908 nm continuous wave Tm:YLF laser. Based on the stimulated Raman scattering effect of SrWO 4 crystal, the fundamental wavelength of 2122 nm was converted into the Raman wavelength of 2637.5 nm, corresponding to the Raman shift of 921 cm−1. The output characteristics of SrWO 4 Raman laser were investigated at various repetition frequencies. The maximum average output power was 720 mW at the 6.6 W absorbed pump power and 4 kHz repetition frequency. The maximum single pulse energy and peak power were 196 μJ and 10.9 kW at the 5.6 W absorbed pump power and 3 kHz repetition frequency, respectively. The pulse Raman laser near 2.6 µm has potential applications in material processing, spectroscopy, remote sensing, and nonlinear frequency conversion. [ABSTRACT FROM AUTHOR]

A series of wide-range-tunable light emissive SrWO 4 :Sm 3+ , SrWO 4 :Sm 3+ ,Eu 3+ phosphors were synthesized via the simple co-precipitation method. The charge compensation can greatly improve SrWO 4 : Sm 3+ phosphors luminous intensity. The critical distance, η T and energy transfer mechanism of SrWO 4 :0.01Sm 3+ ,0.12Eu 3+ were studied. These obtained phosphors exhibit a high luminous efficiency, purity and lower color temperature of the comfortable warm white LEDs. Hues varying have been generated by appropriately tuning the Sm 3+ ions concentration, excitation wavelength or Sm 3+ , Eu 3+ co-doping, which have the color tunable wide gamut light covering the yellow–green, greenish-yellow, yellow, yellow orange, orange, reddish orange and red chromaticity region. In particular, SrWO 4 :0.01Sm 3+ ,0.12Eu 3+ phosphors excited at 404 and 480 nm have higher color saturation than commercially available Y 2 O 2 S:Eu 3+ red phosphor. These phosphors can be excited efficiently using commercial ultraviolet, blue laser diodes and LEDs, and can be used for developing new color light sources, fluorescent display devices, ultraviolet-sensors and tunable visible lasers. [ABSTRACT FROM AUTHOR]

Abstract: SrWO4 and SrWO4:xEu3+ powders were synthesized by the method of microwave radiation heating. The synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and luminescence measurements. The XRD patterns show that SrWO4 and SrWO4:Eu3+ samples can be indexed as a pure tetragonal scheelite structure. The SEM results show that SrWO4 and SrWO4:Eu3+ samples have spherical morphologies. The surfactant of sodium dodecyl sulfonate (SDS) plays an important role in the formation of spheres. And Ostwald ripening may be the general mechanism in the process. The excitation spectrum of SrWO4 sample exhibits a broad absorption band peaked at 294nm due to the charge-transfer transition in the WO4 2− anion. Upon excitation at 294nm, SrWO4 sample exhibits a broad luminescence in the blue spectral range originating from the charge transfer transitions within the WO4 2− group. The excitation spectrum of SrWO4:Eu3+ sample includes a strong absorption band centered at 295nm and weak peaks centered at 389 and 467nm. The emission peaks of SrWO4:Eu3+ sample at 589 and 616nm can be attributed to the 5D0→7F j (j=1 and 2) transitions of Eu3+. The quenching concentration of Eu3+ in SrWO4:Eu3+ sample is 0.04. [Copyright &y& Elsevier]

Abstract: SrWO4 crystallites with various morphologies were synthesized simply by adjusting electrolyte composition in an electrochemical-assisted precipitation process. The structure and morphology characterization of the products were investigated by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). Results indicate that spindle-like, pillar-/needle-like and flower-like SrWO4 crystallites with scheelite structure can be obtained by respectively introducing ethylene glycol (DEG), ethanol (EG) and polyethylene glycol (PEG400) into the electrolyte. Ultraviolet–visible (UV–vis) adsorption spectra and photoluminescence (PL) spectra have shown that the optical properties of the products are greatly influenced by their morphologies. SrWO4 flowers exhibit the strongest absorption ability in UV region and the weakest photoluminescence intensity centered at about 475nm. [Copyright &y& Elsevier]

Abstract: This paper reports our initial research to obtain SrWO4 microcrystals by the injection of ions into a hot aqueous solution and their photocatalytic (PC) properties. These microcrystals were structurally characterized by X-ray diffraction (XRD), Rietveld refinements and Fourier transform (FT)-Raman spectroscopy. The shape and average size of these SrWO4 microcrystals were observed by field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). In addition, we have investigated the PC activity of microcrystals for the degradation of rhodamine B (RhB) and rhodamine 6G (Rh6G) dyes. XRD patterns, Rietveld refinement data and FT-Raman spectroscopy confirmed that SrWO4 microcrystals have a scheelite-type tetragonal structure without deleterious phases. FT-Raman spectra exhibited 12 Raman-active modes in a range from 50 to 1000cm−1. FE-SEM and TEM images suggested that the SrWO4 microcrystals (rice-like – 95%; star-, flower-, and urchin-like – 5%) were formed by means of primary/secondary nucleation events and self-assembly processes. Based on these FE-SEM/TEM images, a crystal growth mechanism was proposed and discussed in details in this work. Finally, a good PC activity was first discovered of the SrWO4 microcrystals for the degradation of RhB after 80 min and Rh6G after 50 min dyes under ultraviolet-light, respectively. [Copyright &y& Elsevier]

A convenient microwave-assisted process has been applied to prepare Scheelite-type SrWO4 microcrystals. The phase structures and morphologies of the products obtained at different time have been characterized by X-ray diffraction, transmission electron microscopy, and field-emission scanning electron microscopy. The results show that SrWO4 with various morphologies including nanoparticles, nanorod, dumbbell, and sphere shapes were synthesized. A possible mechanism to illustrate the formation of the SrWO4 structures was discussed. The examination of photoluminescence (PL) property revealed that their PL emission properties of the as-prepared SrWO4 microcrystals can be dependent on the morphologies, degree of crystal, and sizes of SrWO4. [ABSTRACT FROM PUBLISHER]

SrMoO4 and SrWO4 nanocrystals have been synthesized using Sr(NO3)2 and Na2MeO4 (Me = Mo and W) in ethylene glycol by a microwave irradiation method at 50% of 180 W for 20 min. The product phases were detected using X-ray and selected area electron diffractions. They show the body-centered primitive tetragonal structure with the lattice parameters of a = b = 5.4007 Å and c = 12.0330 Å for SrMoO4, and a = b = 5.4274 Å and c = 11.9241 Å for SrWO4. X-ray diffraction patterns of the products, obtained by simulation using CaRIne version 3.1 program, are in accordance with those of the corresponding experiment and International Centre for Diffraction Data. A transmission electron microscope revealed the presence of nanocrystals composing the products, with their sizes in the ranges of 14–40 and 14–38 nm for SrMoO4 and SrWO4, respectively. Six different vibrations of ν1( Ag), ν3( Bg), ν3( Eg), ν4( Bg), ν2( Ag), and νf.r.( Ag) were detected using a Raman spectrometer, and the ν3( F2) antisymmetric stretching and ν4( F2) bending modes of [MeO4]2− tetrahedrons using a Fourier transform infrared spectrometer. Photoluminescence emissions of SrMoO4 and SrWO4, caused by the 1 T2 → 1 A1 transition of electrons, were detected at 410 and 418 nm, respectively. [ABSTRACT FROM AUTHOR]

Strontium tungstate is a well-known stimulated Raman scattering laser material. The unique structure of this crystal allows the usage of these crystals as matrices for laser active elements with nonlinear self-conversion of radiation to a new spectral range. The recent advances in crystal growth, particle and thin film fabrication, spectroscopy, and laser properties were reviewed. The demonstration of laser output of neat and Nd3+-doped SrWO4 crystal shows that it is an efficient self-stimulated Raman scattering laser. [ABSTRACT FROM AUTHOR]

Abstract: The electronic structures of the SrWO4 crystals containing F-type color centers are studied within the framework of the fully relativistic self-consistent Dirac–Slater theory using a numerically discrete variational (DV-Xα) method. The calculations indicate that either F or F+ center has donor energy level within the forbidden band. The electronic transition energies from the two donor levels to the bottom of the conduction band are 1.82eV and 2.28eV corresponding to the 685nm and 545nm absorption bands, respectively. It is, therefore, concluded that the 545–685nm absorption bands are originated from the F and F+ center in SrWO4 crystal respectively. [Copyright &y& Elsevier]

[Display omitted] • Fe-SrWO 4 specific surface area was 3.154, 9.991, 14.541 m2/g. • 0.02 M Fe-SrWO 4 delivered excellent durability and high conductivity. • 0.02 M Fe-SrWO 4 delivered elevated HER with low overpotential and Tafel slope. • ECSA were 26.7, 79.1 and 98.8 mF/cm2for alkaline electrolyte. • ECSA were 8.6, 24.9 and 93.3 mF/cm2 for alkaline natural seawater electrolyte. Water splitting is a popular method to make hydrogen and oxygen gas, and it is one of the risen methods for overcoming energy shortage. Recently, the main challenge is to prepare the efficient materials at a low cost, earth-abundant, high durability, and catalytic action for water splitting applications. In this present work, the pristine and different molar concentrations of Fe doped SrWO 4 was produced via simple co-precipitation technique. The high crystalline peak at 27.6° explored (1 1 2) crystal plane confirmed the SrWO 4 formation. In Raman spectra, active modes such as stretching and bending vibrations of [WO 4 ]2- tetrahedron confirmed the existence of SrWO 4. The flower-like morphology was briefly investigated by using SEM characterization. Moreover, the elements such as Sr, W, O and Fe were existed in proper ratio, which also confirmed the formation of SrWO 4. The prepared electrocatalysts was tested by two different electrolytes such as 1 M KOH electrolyte and seawater + 1 M KOH electrolytes. In addition, electrochemical measurements of electrocatalysts prepared with and without Fe doping were characterized and compared. The overpotential of the prepared electrocatalysts including SW1, SW2 and SW3 were 206, 182, 154 mV (for alkaline electrolyte) and 261, 198, 172 mV (for alkaline natural seawater electrolyte). In both electrolytes, 0.02 M Fe doped SrWO 4 explored outstanding HER action and high durability because of existence of elevated surface area and exclusive morphology. Hence, the present study recommends developing strontium based materials in electrochemical hydrogen evolution reaction. [ABSTRACT FROM AUTHOR]

Abstract: SrWO4 powders were synthesized by the co-precipitation method and processed in a microwave-hydrothermal (MH) at 140 °C for different times. The obtained powders were analyzed by X-ray diffraction (XRD), micro-Raman (MR) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, field-emission gun scanning electron microscopy (FEG-SEM), ultraviolet–visible (UV–vis) absorption spectroscopy and photoluminescence (PL) measurements. XRD patterns and MR spectra showed that the SrWO4 powders present a scheelite-type tetragonal structure without the presence of deleterious phases. FT-IR spectra exhibited a high absorption band situated at 831.57 cm−1, which was ascribed to the Wmetric stretching vibrations into the [WO4] tetrahedron groups. FEG-SEM micrographs suggested that the processing time is able to influence in the growth process and morphology of SrWO4 powders. UV–vis absorption spectra revealed different optical band gap values for these powders. A green PL emission at room temperature was verified in SrWO4 powders when excited with 488 nm wavelength. [Copyright &y& Elsevier]

Abstract: Metal tungstates (MeWO4, Me=Ba, Sr and Ca) were successfully prepared using the corresponding Me(NO3)2·2H2O and Na2WO4·2H2O in ethylene glycol by the 5h sonochemical process. The tungstate phases with scheelite structure were detected with X-ray diffraction (XRD) and selected area electron diffraction (SAED). Their calculated lattice parameters are in accord with those of the JCPDS cards. Transmission electron microscopy (TEM) revealed the presence of nanoparticles composing the products. Their average sizes are 42.0±10.4, 18.5±5.1 and 13.1±3.3nm for Me=Ba, Sr and Ca, respectively. Interplanar spaces of the crystals were also characterized with high-resolution TEM (HRTEM). Their crystallographic planes are aligned in systematic array. Six different vibration wavenumbers were detected using Raman spectrometer and are specified as ν 1(Ag), ν 3(Bg), ν 3(Eg), ν 4(Bg), ν 2(Ag) and free rotation. Fourier transform infrared (FTIR) spectra provided the evidence of scheelite structure with W–O anti-symmetric stretching vibration of [WO4]2− tetrahedrons at 786–883cm−1. Photoluminescence emission of the products was detected over the range of 384–416nm. [Copyright &y& Elsevier]

Abstract: Nanocrystalline SrWO4 was successfully prepared using SrCl2 and Na2WO4 in ethylene glycol at different pH values, microwave powers and prolonged times. The phase was detected using XRD and SAED. TEM, HRTEM, SEM and particle size distribution revealed the presence of nano-sized crystals with their crystallographic planes aligning in systematic order. Raman and FTIR spectra provide the evidence of scheelite structure with W–O stretching vibration in tetrahedrons at 781–912cm−1. PL emission of the products is considered to be from the 1T2 → 1A1 transition of electrons within [WO4]2− tetrahedrons at 420–428nm (2.901–2.956eV). [Copyright &y& Elsevier]

The polycrystalline materials of SrWO4 were synthesized by means of a solid phase reaction with analytical purity SrCO3 and WO3 at high temperature. The transparent SrWO4 single crystal with dimension of ϕ 22 mm×40 mm has been successfully grown along a-axis by Czochralski method. X-ray powder diffraction results show that the as-grown SrWO4 single crystal belongs to tetragonal system and I41/a space group. The measured density of SrWO4 is 6.439 g·cm−3 by buoyancy method. The effective segregation coefficients of W and Sr elements in SrWO4 single crystal are close to 1 by the X-ray fluorescence method. [ABSTRACT FROM AUTHOR]

Abstract: AWO4 (A=Ca, Ba, Sr) nanofilms on a glass substrate are prepared through the combination of the reverse micelle system with the dip-coating technology, in which collodion is used as a dispersant and film-forming agent. The nanofilms are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), photoluminescence (PL) and IR spectra, respectively. The results indicate that the tungstate nanoparticles having a tetragonal scheelite structure are well distributed on the substrate. PL results indicate that a blue-shift emission band peak of the nanofilms appears when they are excited at 240nm relative to those of the bulk materials, and a red-shift emission band peak of nanofilms appears compared with nanoparticles, which can be attributed to the quantum size effect. IR spectra reveal that a large absorption band, which is ascribed to the W–O stretching vibration in WO4 tetrahedron, is observed around 820cm−1. [Copyright &y& Elsevier]

Abstract: We have investigated the stability of AZrO3 and AWO4 (A=Ba, Sr and Ca) in the ErBa2Cu3O y (Er123) matrix, and the effect of their addition on the superconducting properties of Er123. No degradation of T c(zero) was observed for the Er123 samples with BaZrO3 and SrZO3 addition up to 0.5wt.%, and with BaWO4 and SrWO4 addition up to 1.0wt.%. T c(onset) was not affected by the AZrO3 and AWO4 addition for all the samples. The BaZrO3-added samples showed uniform distribution of BaZrO3 fine particles. It was found that BaZrO3 and BaWO4 were most stable in the Er123 matrix among AZrO3 and AWO4 materials. [Copyright &y& Elsevier]

Stoichiometric CaWO4 and SrWO4 thin films were synthesized using a chemical solution processing, the so-called polymeric precursor method. In this soft chemical method, soluble precursors such as strontium carbonate, calcium carbonate and tungstic acid, as starting materials, were mixed in an aqueous solution. The thin films were deposited on glass substrates by means of the spinning technique. The surface morphology and crystal structure of the thin films were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Nucleation stages and surface morphology evolution of the thin films on glass substrates were studied by atomic force microscopy. The films nucleate at 300 °C, after the coalescence of small nuclei into larger grains yielding a homogeneous dense surface. XRD characterization of these films showed that the CaWO4 and SrWO4 phases crystallize at 400 °C from an inorganic amorphous phase. No intermediate crystalline phase was identified. The optical properties were also studied. It was found that CaWO4 and SrWO4 thin films have an optical band gap, Egap=5.27 and 5.78 eV, respectively, of a direct transition nature. The excellent microstructural quality and chemical homogeneity confirmed that this soft solution processing provides an inexpensive and environmentally friendly route for the preparation of CaWO4 and SrWO4 thin films. [Copyright &y& Elsevier]

The polyacrylamide gel method combined with low temperature calcination technology have been used to synthesize the SrMoO 4 /SrWO 4 micro/nano heterojunction phosphors with excellent photoluminescence properties. The effects of mass ratio of SrMoO 4 /SrWO 4 on the phase structure, microstructure, charge state, photoluminescence performance and photocatalytic activity of SrMoO 4 /SrWO 4 phosphors were systematically studied. Various characterization methods jointly confirmed that SrMoO 4 and SrWO 4 formed a special interface contact, generated a large number of oxygen vacancies, and then promoted the transfer and recombination of charge carriers, and further enhanced the photoluminescence properties of SrMoO 4 /SrWO 4 micro/nano heterojunction phosphors. The SrMoO 4 /SrWO 4 micro/nano heterojunction phosphors exhibits novel emission peak at 440 nm with the excitation wavelength of 310 nm and the ultraviolet intrinsic emission peak at 378 nm of SrMoO 4. Photocatalytic experiments further confirmed that the SrMoO 4 /wt 5% SrWO 4 micro/nano heterojunction phosphors have high charge transfer and recombination rates, demonstrating high photoluminescence properties for the SrMoO 4 /SrWO 4 micro/nano heterojunction phosphors. This new idea provides a technical reference for the construction of heterojunction phosphor with special interface contact and its application in LED and laser fields. • Polyacrylamide gel method have been used to synthesize the heterojunction phosphors. • A novel photoluminescence phenomenon for the heterojunction phosphors was observed. • A photoluminescence mechanism of heterojunction phosphors was proposed. [ABSTRACT FROM AUTHOR]

Abstract: Well-crystallized SrWO4 products with kayak-like shapes were synthesized by a microemulsion method. In addition, various other morphologies including peanut, dumbbell, and notched sphere shapes were synthesized using a simple precipitation reaction. As the molar ratio of [WO4 2−] to [Sr2+] was increased, the morphology of the SrWO4 crystals evolved from rods, through peanut-like structures and dumbbells, to notched spheres. This morphology evolution of SrWO4 crystals is attributed to a fractal mechanism. [Copyright &y& Elsevier]

Rapid-monitoring of drugs has attracted tremendous consideration owing to robust global demand for cost-effective and high effectiveness. Binary metal oxides with various morphology have been reported as electrodes for electrochemical sensor to fulfilling the clinical and enviromental requirements. In this study, strontium tungstate (SrWO 4) nanoflakes have been successfully prepared via the facile sonochemical method for the first time. The characteristics of as-prepared SrWO 4 are systematically measured by various analytical and spectroscopic methods. The SrWO 4 nanoflakes are utilized to modify the electrochemical electrode for the sulfadiazine (SDZ) determination. The SrWO 4 modified electrode possesses excellent electrocatalytic activity and high recognition capability for the electrochemical detection of SDZ. Impressively, the as-fabricated SrWO 4 modified electrode attainted lowest oxidation peak at +0.93 V (vs Ag/AgCl 2) with the limit of detection of 0.009 μM, the sensitivity of 0.123 µA µM−1 cm2 and linear detection range of 0.05–235 μM. The enhanced performance of proposed SrWO 4 -based sensors could be attributed to the catalytic effect, large surface area, good electrical conductivity and physicochemical nature. Notably, the electrocatalytic performances of the SDZ sensors are good as compared to the previous literature, indicating the significance of the newly designed SrWO 4 modified electrode. The real-sample diagnosis by the SDZ detection in environmental sample demonstrates the proposed SrWO 4 -based sensors with good recovery range. ga1 • The SrWO 4 was prepared by sonochemical technique. • The SrWO 4 modified electrode was applied towards the determination of sulfadiazine. • The SrWO 4 modified electrode exhibits a good electrocatalytic activity with low limit of detection, wide linear range and sensitivity. • The SrWO 4 modified electrode showed a proficient sensing ability in water samples. [ABSTRACT FROM AUTHOR]

Tb3+ doped glass ceramics containing SrWO 4 crystals are prepared by melting crystallization method and their luminescence properties are studied. It is determined by DSC that the heat treatment temperature is 730℃ and the time is 2h. Through the XRD of the glass ceramics, it can determine the crystalize phase is SrWO 4 after comparing with PDF normal card. In the emission spectrum of the Tb3+ doped SrWO 4 glass ceramics samples, there are two obvious emission peaks at 490nm and 544nm corresponding to the transitions of 5D 4 →7F 6 and 5D 4 →7F 5 of Tb3+. Based on the fluorescence spectrum, it can be determined that the optimum concentration of Tb 4 O 7 is 1.0 mol, and the fluorescence lifetime is 2.16 ms. [ABSTRACT FROM AUTHOR]