6 research outputs found
Fast microwave synthesis and white luminescent emission from Pb1–2xCaxSrxMoO4 (x=0; 0.3; and 0.5) particles
Scheelite with ABO4 structure has been increasingly highlighted in the optoelectronic field. In this study, PbMoO4, Pb0.4Ca0.3Sr0.3MoO4, and Ca0.5Sr0.5MoO4 particles were fast synthesized via microwave-assisted hydrothermal method for 1, 2, 4, and 8 min. The particles were characterized by X-ray diffraction (XRD) and Rietveld refinement, ultraviolet-visible (UV–vis) absorption spectroscopy, photoluminescence (PL), and field emission scanning electron microscopy (FE-SEM). The diffractogram showed a scheelite-type tetragonal structure and a unit cell with space group I41/a, as well as the presence of defects with an increase in the synthesis time in PbMoO4 and Pb0.4Ca0.3Sr0.3MoO4 samples. Rietveld refinement data possibilities the evaluation of distortions in the tetrahedral [MoO4] clusters and FE-SEM images showed octahedral, spherical particles, and flower-like morphology due to the additions of calcium and strontium in the structure. The bandgap of the materials varied between 3.32 and 4.18 eV, which was affected by the increase in the presence of dopants in the materials. The photoluminescence presented by the PL emission spectral showed a typical emission peak in green with the PL signal intensity decreasing with the synthesis time increase for the PCSMO samples, and the longer the synthesis time, the higher the PL signal for CSMO samples. CCT coordinates have been calculated for all samples and its value exhibited that, overall emission is near white light. This parameter infers that Pb0.4Ca0.3Sr0.3MoO4 sample, synthesized in 1 min, may have potential application in commercial LEDs, due to near white emission and fast microwave synthesis
Spray pyrolysis synthesis and characterization of Mg1-xSrxMoO4 heterostructure with white light emission
[EN] Molybdates are inorganic materials with great potential in white phosphors application, being an alternative to traditional lighting sources. In this study, we report the synthesis and characterization of Mg1-xSrxMoO4 (x = 0, 0.25, 0.50, 0.75, and 1) powders with white light-emitting properties. Using X-ray diffraction, the formation of the monoclinic beta-MgMoO4 phase was observed for x = 0 and the formation of the tetragonal scheelite phase of SrMoO4 was observed for x = 1. The formation of a heterostructure composed of both phases was found for compositions with x = 0.25, 0.50 and 0.75. Scanning and trasmission electron microscopy images showed that the Mg1-xSrxMoO4 particles exhibit a spherical morphology formed by several primary nanoparticles. Raman scattering spectroscopy enabled the accurate identification of the Raman modes for different compositions and their assignment to either the SrMoO4 or beta-MgMoO4 modes. The bandgap energies were determined to fluctuate between 4.25 eV and 4.44 eV, being influenced by the degree of structural disorder. The photoluminescence emission spectra of the nanoparticles showed neutral- and cool-white emission with high-quality white light (CRI > 80%). The samples synthesized with x <= 0.50 are potential materials for the application in LED lamps (6500 K) and pure white-light sources (5500 K).The authors thank the following Brazilian and Spanish research financing institutions for financial support: A.A.G. Santiago acknowledges financial support from the National Council for Scientific and Technological Development -CNPq, the Graduate Program in Materials Science and Engineering (PPGCEM-UFRN) and the Coordination for the Improvement of Higher Education Personnel (CAPES) -Brazil (CAPES) -Finance Code 001. F.J.M. and D.E. acknowledge financial support from the Spanish Ministerio de Ciencia, Innovacion y Universidades, the Spanish Agencia Estatal de Investigacion (AEI), and the Fondo Europeo de Desarrollo Regional (FEDER) under Grants No. MAT2016-75586-C4-1/2-P and from the Generalitat Valenciana under Grant Prometeo/2018/123 - EFIMAT.Santiago, AAG.; Tranquilin, RL.; Botella, P.; Manjón, F.; Errandonea, D.; Paskocimas, CA.; Motta, FV.... (2020). Spray pyrolysis synthesis and characterization of Mg1-xSrxMoO4 heterostructure with white light emission. Journal of Alloys and Compounds. 813:1-13. https://doi.org/10.1016/j.jallcom.2019.152235S113813Gao, Z., Sun, P., Zhong, Y., Yu, R., & Deng, B. (2019). Eu3+-doped highly thermal-stable barium yttrium aluminate as a red-emitting phosphor for UV based white LED. Optics & Laser Technology, 111, 163-168. doi:10.1016/j.optlastec.2018.09.026Zhong, J., Chen, X., Chen, D., Liu, M., Zhu, Y., Li, X., & Ji, Z. (2019). 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