Presence of excited electronic state in CaWO4 crystals provoked by a tetrahedral distortion: An experimental and theoretical investigation

Abstract

By combining experimental techniques such as x-ray diffraction, Fourier transform Raman, ultraviolet-visible, x-ray absorption near edge structure, extended x-ray absorption fine structure spectroscopy, and theoretical models, a general approach to understand the relationship among photoluminescence (PL) emissions and excited electronic states in CaWO 4 crystals is presented. First-principles calculations of model systems point out that the presence of stable electronic excited states (singlet) allow us to propose one specific way in which PL behavior can be achieved. In light of this result, we reexamine prior experiments on PL emissions of CaWO 4 .

Pycnometric and Spectroscopic Studies of Red Phosphors Ca2+(1-1.5x)WO4:Eu3+xand Ca2+(1-2x)WO4:Eu3+x,Na+x

“…This trend is more apparent for Ca (1−1.5x) Eu x WO 4 , which has vacancies in the structure. The positions and shapes of each peak are almost identical with those of Gracia et al 19 and Cavalcante et al 20 In Figure 5, the positions of Figure 5. FT-Raman spectra of CaWO4, Ca0.85Eu0.10WO4, and Ca0.80Eu0.10Na0.10WO4.…”

A combined theoretical and experimental study of electronic structure and optical properties of β-ZnMoO4 microcrystals

“…Gracia et al [78] have demonstrated that the CCCT mechanism in CaWO 4 crystals at excited states (excited singlet and excited triplet) can be considered a new class of electronic transitions which are involved in PL emissions. In this work, we consider that within the β-ZnMoO 4 lattice, the octahedral [ Intensity (arb.…”

Potentiated Electron Transference in α-Ag2WO4 Microcrystals with Ag Nanofilaments as Microbial Agent

“…7 Breaking symmetry processes of these clusters such as distortions, breathings, and tilts create a huge number of different structures; this phenomenon can be related to short-, intermediate-and long-range structural order−disorder that subsequently creates different materials properties. Therefore, for a α-Ag 2 WO 4 material, structural and electronic properties can primarily be associated with cluster constituents, and the disparity or mismatch of both clusters can induce structural order−disorder effects that will significantly influence their luminescence and photodegradation processes.…”