Structural refinement, growth process, photoluminescence and photocatalytic properties of (Ba1-xPr2x/3)WO4 crystals synthesized by the coprecipitation method

Abstract

Barium praseodymium tungstate (Ba 1-x Pr 2x/3 )WO 4 crystals with (x = 0, 0.01, and 0.02) were prepared by the coprecipitation method. These crystals were structurally characterized by X-ray diffraction (XRD), Rietveld refinements, Fourier-transform Raman (FT-Raman) and Fourier-transform infrared (FT-IR) spectroscopies. The shape and size of these crystals were observed by field emission scanning electron microcopy (FE-SEM). Their optical properties were investigated by ultraviolet visible (UV-vis) absorption and photoluminescence (PL) measurements. Moreover, we have studied the photocatalytic (PC) activity of crystals for degradation of rhodamine B (RhB) dye. XRD patterns, Rietveld refinements data, FT-Raman and FT-IR spectroscopies indicate that all crystals exhibit a tetragonal structure without deleterious phases. FT-Raman spectra exhibited 13 Raman-active modes in a range from 50 to 1000 cm 21 , while FT-IR spectra have 8 infrared active modes in a range from 200 to 1050 cm 21 . FE-SEM images showed different shapes (bonbon-, spindle-, rice-and flake-like) as well as a reduction in the crystal size with an increase in Pr 3+ ions. A possible growth process was proposed for these crystals. UV-vis absorption measurements revealed a decrease in optical band gap values with an increase of Pr 3+ into the matrix. An intense green PL emission was noted for (Ba 1-x Pr 2x/3 )WO 4 crystals (x = 0), while crystals with (x = 0.01 and 0.02) produced a reduction in the wide band PL emission and the narrow band PL emission which is related to f-f transitions from Pr 3+ ions. High photocatalytic efficiency was verified for the bonbon-like BaWO 4 crystals as a catalyst in the degradation of the RhB dye after 25 min under UV-light. Finally, we discuss possible mechanisms for PL and PC properties of these crystals.

Crystal growth and photoluminescence of europium-doped strontium titanate prepared by a microwave hydrothermal method

“…This phenomenon can be explained by new electronic levels related to additional 4f orbitals of Eu 3 þ ions. Cavalcante et al [22] achieved a significant reduction in E gap values (from 4.9 to 3.82 eV) upon the replacement of Ba 2 þ by Pr 3 þ in the BaWO 4 lattice. They reported that Pr 3 þ ions induce the appearance of a new intermediary energy level within the optical band gap, since the praseodymium contributes 4f orbitals, while the barium exhibits 6 s orbitals in the valence band.…”

Synthesis and morphological transformation of BaWO4 crystals: Experimental and theoretical insights

“…Barium tungstate (BaWO 4 ) crystals have attracted significant interest from many research groups due to their potential applications in scintillation devices, batteries, capacitors, photocatalysts, and, in particular, photoluminescent materials [1][2][3][4][5][6]. In recent years, various synthetic methods have been used to produce BaWO 4 crystals, such as co-precipitation (CP), sol-gel, modified Pechini, solid state reaction, solution route, Czochralski, sonochemical, and hydrothermal techniques [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24].…”

Microwave-assisted hydrothermal synthesis of Ag2(W1-xMox)O4 heterostructures: Nucleation of Ag, morphology, and photoluminescence properties

“…According to Longo et al [8], the emission in the red spectrum is most likely related to the [AgOy] clusters. In this manner, an increase in the violet PL emission in the Ag 2 W 0.50 Mo 0.50 O 4 sample is also related to order-disorder effects, which significantly influence the luminescence properties of the tungstates [37].…”