Rietveld refinement, morphology and optical properties of (Ba_1−xSr_x)MoO₄crystals

Abstract

In this article, the structural refinement, morphology and optical properties of barium strontium molybdate [(Ba1−xSrx)MoO4 with x = 0, 0.25, 0.50, 0.75 and 1] crystals, synthesized by the co‐precipitation (drop‐by‐drop) method, are reported. The crystals obtained were structurally characterized by X‐ray diffraction (XRD), Rietveld refinement, and Fourier transform–Raman (FT–Raman) and Fourier transform–infrared (FT–IR) spectroscopies. The shapes of the crystals were observed by means of field‐emission scanning electron microscopy (FE‐SEM). The optical properties were investigated using ultraviolet–visible (UV–Vis) absorption spectroscopy and photoluminescence (PL) measurements. XRD patterns, Rietveld refinement, and FT–Raman and FT–IR spectra showed that all of the crystals are monophasic with a scheelite‐type tetragonal structure. The refined lattice parameters and atomic positions were employed to model the [BaO8], [SrO8] and [MoO4] clusters in the tetragonal lattices. The FE‐SEM images indicate that increased x content produces a decrease in the crystal size and modifications in the crystal shape. UV–Vis spectra indicated a decrease in the optical band gap with an increase in x in the (Ba1−xSrx)MoO4 crystals. Finally, a decrease in the intensity of PL emission is apparent with an increase in x up to 0.75 in the (Ba1−xSrx)MoO4 crystal lattice when excited by a wavelength of 350 nm, probably associated with the degree of structural order–disorder.

Structural, Optical, and Magnetic Properties of NiMoO4 Nanorods Prepared by Microwave Sintering

“…PL emission is considered a powerful tool to obtain information on the electronic structure and degree of structural organization at medium range of the materials [46–49]. The PL spectrum of the α , β -NiMoO 4 nanostructures shows a broad band covering a large part of the visible spectrum with a maximum situated at 480 nm (blue emission), when excited by a 350.7 nm laser line (see Figure 5).…”

Temperature dependence of scintillation properties of SrMoO4

“…The main motif of this structure is an oxyanion complex MoO 4 2-surrounded by eight Sr 2+ cations [24]. Since the bottom of the conduction band and the top of the valence band are formed mainly by molybdenum and oxygen states [25], the oxyanion complex determines the main optical properties of the crystal.…”

Effect of cation vacancies on the crystal structure and luminescent properties of Ca 0.85−1.5x Gd x Eu 0.1 □ 0.05+0.5x WO 4 (0 ≤ x ≤ 0.567) scheelite-based red phosphors

“…However, in stoichiometric scheelites (a = b in the formula), ordering between the A'/A'' cations is rare. Typically, it is realized when the ionic radius of A' is about 0.35 Å larger than that of A'', provided that the A' cation has a formal charge larger than that of A'' [18][19][20][21][22][23][24]. On the other hand, scheelite-based materials can accommodate a large amount of vacancies in the A sublattice (compounds with a < b) [25][26][27][28][29] In these structures, A'/A'' cation ordering is more common, because it is also coupled to the ordering between cations and vacancies; and can occur for the A'/A'' ionic radii differences as low as ∼ 0.1 Å.…”