Structural and Optical Properties of Ca_0.9Cu_0.01WO₄ Solid Solution Synthesized by Sonochemistry Method at Room Temperature

Abstract

In this work, we report the room-temperature synthesis of pure calcium tungstate (CaWO 4 ) and copper-doped calcium tungstate solid solution (Ca 0.99 Cu 0.01 WO 4 ) by using a sonochemistry method. These materials were structurally characterized by X-ray diffraction (XRD) and Raman spectroscopy. The obtained XRD patterns were submitted to a Rietveld refinement showing, in both materials, a tetragonal phase with space group and point group of I4 1 /a and C 4h 6 , respectively. Microscopy images of both materials, obtained by field emission scanning electron microscopy, showed spherical agglomerated structures composed by spherical nanoparticles, while calcium and tungstate elements were identified by energy-dispersive X-ray spectroscopy for pure calcium tungstate and copper, calcium, and tungstate for Ca 0.99 Cu 0.01 WO 4 solid solution. The decrease of optical band gap (E gap ) from 4.0 eV (CaWO 4 ) to 3.45 eV (Ca 0.99 Cu 0.01 WO 4 ) confirmed the substitution of calcium atoms for copper atoms in the clusters [CaO 8 ]. Maximum photoluminescence (PL) emission was shifted from 522 nm in the pure CaWO 4 to 475 nm in the Ca 0.99 Cu 0.01 WO 4 solid solution. Consequently, there was an increase of PL emissions intensity in the blue and green regions of the visible spectrum, due to electronic transitions between the orbitals O 2p, Cu 3d, and W 5d.

Sonochemical Synthesis and Characterization of the Biphasic Compound Na2Ti3O7/ Na2Ti6O13

“…The detailed study regarding the phase composition and the unit cell parameters was performed using the Rietveld refinement method via the FullProf package software 9 . The lattice parameters (a, b, c, α, β, γ), unit cell volume (V) atomic coordinates (x, y, z), background, Cagliote parameters of Pseudo-Voigt function (U, V and W), thermal anisotropic factor (B iso ) and occupation, O cc were also refined 1,[10][11][12][13][14][15] . The quality of computed data was checked using R quality indicators (R exp , R p , R wp and χ 2 ), as well as the profile of the residual line (Y obs -Y cal ) 16 .…”

Rietveld Refinement, Morphology, and Optical and Photoluminescence Properties of a β-Ag1.94Cu0.06MoO4 Solid Solution

“…In addition, the summarized values for the strain and crystallite size are displayed in Table . On the basis of the WH plot, it is observed that the slope obtained for the β-Ag 2 MoO 4 sample is −8.65(5) × 10 –5 , indicating the lower contribution of the strain in the broad line of the diffraction peaks . On the other hand, the WH plot for β-Ag 1.94 Cu 0.06 MoO 4 was 30.69(5) × 10 –5 .…”

“…Molybdenum oxide compounds are a well-known semiconductor family that has been investigated for several applications such as catalysts, − sensors, , photocatalysts, , microbial agents, , and photoluminescence (PL). − Silver molybdate (Ag 2 MoO 4 ) is an important member of this family and has two polymorphs: α-Ag 2 MoO 4 with a tetragonal structure and α-Ag 2 MoO 4 , which exhibits a cubic spinel-like structure. ,, Therefore, stick, flower, and potato morphologies have been synthesized for these materials. β-Ag 2 MoO 4 has aroused great interest because of its good chemical stability at high temperatures, in addition to presenting a range of applications in different fields including energy storage, antimicrobial agents, , photocatalysis, , and PL. , However, β-Ag 2 MoO 4 has an effective photon absorption in the ultraviolet region, which is limited to several photonics applications. , For this reason, the insertion of dopants on these materials such as rare-earth metals have been extensively studied .…”

Ag2–xCuxWO4 Solid Solution: Structure, Morphology, Optical Properties, and Photocatalytic Performance in the Degradation of RhB under Blue Light-Emitting Device Irradiation

“…The photocatalytic activity of semiconductors has been recently correlated with the band potentials edge of semiconductors, , in this case, through the optical band gap values and the total electronegativity of semiconductors. Therefore, the valence band ( E VB ) and conduction band ( E CB ) edge potentials can be estimated for a pure semiconductor, solid solution, or heterojunction.…”

“…The partial replacement of cations in the host matrix by copper ions resulted in solid solutions with interesting properties, mainly regarding the photocatalytic, − magnetic, electrical, and optical properties . Moreover, the investigation of copper-doped silver tungstate was completely absent in the literature until now.…”