Contribution of structural order-disorder to the green photoluminescence ofPbWO4

Abstract

An intense and broad visible photoluminescence ͑PL͒ band was observed at room temperature in structurally disordered PbWO 4 thin films. The scheelite lead tungstate ͑PbWO 4 ͒ films prepared by the polymeric precursor method and annealed at different temperatures were structurally characterized by means of x-ray diffraction and atomic force microscopy analysis. Quantum-mechanical calculations showed that the local disorder of the network modifier ͑Pb͒ has a very important role in the charge transfer involved in the green PL emission. The experimental and theoretical results are in good agreement, both indicating that the generation of the intense visible PL band is related to simultaneous structural order and disorder in the scheelite PbWO 4 lattice.

Experimental and theoretical correlation of very intense visible green photoluminescence in BaZrO3 powders

“…Using the same kind of distorted model, we have explained the PL of various perovskite titanates 33,34 , zirconate titanates, 35,36 and tungstates. 37,38 Figure 2 shows the UV-vis absorption spectra of BZO powders annealed at 400, 450, 500, and 700°C for 2 h in an oxygen atmosphere.…”

“…In our model, the wide-band model, 38 the most important events occur before excitation, i.e., before the photon arrives. The short and intermediate-range structural defects generate localized states in the band gap and inhomogeneous charge distribution in the cell, thus allowing for the trapping of elec- …”

Hydrothermal synthesis and photoluminescence properties of cerium-doped cadmium tungstate nanophosphor

“…It is stated in the literature that the blue emission originates from the tetragonal WO 4 2À groups, while the origin of the green emission remains controversial. [17] The intensity of blue-green emission band is more in Figure 5(b) when compared to Figure 5(c). It is due to higher stimulation energy of 263 nm excitation wavelength on comparison with 600 nm excitation wavelength.…”

Estudo, caracterização e propriedades de ortofosfatos multifuncionais

“…Quando ocorre excitação, os elétrons armadilhados acima da BV são promovidos a níveis de energia próximos a BC. No processo de recombinação, ocorre a emissão de fótons com distintas energias, dando origem ao espectro de FL do tipo banda larga [121][122][123].…”

“…Ou seja, com os processos de difusão de matéria, a diferença entre o comprimento e a largura das partículas diminui, evidenciando uma preferência da densificação nos planos {100}. [86,87,197,201,203], além do modelo de banda larga [121]. A estrutura eletrônica da HA perfeita e sem defeitos é constituída por níveis de energia provenientes dos clusters de [PO4] (banda de valência) e Ca (banda de condução) e com energia de gap similar aos apontados para amostras com caráter isolante.…”